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Chromosome aberrations in 50 patients with idiopathic mental retardation and in 50 control subjects
September, 1970
444
The ]ournal of P E D I A T R I C S
Chromosome aberrations in 50 patients Mtb idiopathic mental retardation and in 50 control subjects Madison Blind Study III Analysis of coded, randomized chromosome preparations from 50 mentally retarded patients with three or more anomalies and from 50 normal control subjects revealed chromosomal abnormalities among 8 patients. Seven of these have changes in chromosome structure; the other is triplo-X. In 3 patients the structural abnormality is probably unrelated to the physical and mental defects. One control subject has mosaicism involving sex chromosomes.
Richard F . Daly, M.D. MADISON,
WIS.
S O M E V A R I A T I O N Of chromosomal structure occurs even among apparently normal persons. If, by coincidence, a variant is present in a retarded individual with multiple congenital anomalies, it may be interpreted incorrectly as the cause of his defects. For certain types of chromosome variants, only an extended comparative study of such patients and healthy control subjects can establish whether these variants have serious consequences. Such a study would also help to determine for what fraction of mentally retarded patients whose conditions do not represent a known syndrome a chromosomal causation can be assumed. The present report describes part of a From the University of Wisconsin. Supported by Grant GM-15422 from the National Institutes of Health to Dr. K. Patau. Address: UMvers~ty of Wisconsin, 515 Genetics Building, Madison, Wi$. 53706. Vol. 77, No. 3, pp. 444-453
long-range, continuing study* designed by Prof. Klaus Patau to give information on the incidence of chromosomal abnormalities among a certain class of patients and control subjects. Several participants have analyzed chromosomes (on coded slides) from individuals selected because they had mental retardation combined with at least 3 other anomalies and from an equal number of control subjects. Patients diagnosed as having a known syndrome were excluded. Apart from the very rare instances of diploid-triploid mosaicism, chromosomal aberrations found in live persons belong to either of two classes. One is aneuploidy sensu strictu, i.e., a wrong number of one or a few of the normal chromosomes; the other consists of structural abnormalities of chromosomes. All or most of the viable types of aneuploidy are known. Since the great * F o r parts I a n d I I see S u m m l t t ~ a n d P a t a u . ~T
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Chromosome aberrations in mental retardates
majority of such types, in particular the 3 autosomal trisomies, can be diagnosed clinically, few would get into the present study, unless mosaicism rendered the clinical expression atypical. It could therefore be anticipated that in the present group of patients chromosome abnormalities would often be of the structural kind. Since the number of chromosomes in this group is more often than not normal, the microscopic detection of such aberrations can be difficult or often even impossible. Since bias in interpreting the cytologic findings is a real danger, it is essential that any comparative study such as the present one be conducted blindly. MATERIAL
AND
METHODS
The group described is composed of 50 mentally retarded patients who have at least 3 other anomalies and 50 phenotypically normal control subjects. T h e rationale for establishing the criteria for patient selection is given by Summitt 1 in a recent description of his findings in a portion of this study. Most of the patients were chosen from special classes for retarded children in the Milwaukee school system. Screening of patients to find those meeting the criteria was done by the school physicians, members of the Milwaukee Health Department. T h e remainder were obtained from the Pediatrics Department, University Hospitals, University of Wisconsin, and from the Central Wisconsin Colony and Training School. Either Dr. John Opitz or I made the final selection of patients. Members of the staff and students at the University of Wisconsin served as control subjects. Chromosome preparations were made from the lymphocytes of 10 ml. of venous blood using a slight modification of the technique described by Moorhead and associates. 2 Two slides from each culture were stained with one per cent aceto-orcein, 2 with Feulgen (omitting the SOs washings), and 2 with azur A. Each individual was assigned a code number so that 20 consecutive numbers represented 10 patients and 10 control subjects in a random sequence. All metaphase plates studied were selected for good tech-
445
nical quality and analyzed at the microscope as completely as possible by means of pencil sketches. T h e scheme for determining the number of cells to be analyzed in each case is a routine followed in the blind study and has been described by Summitt. 1 The same procedure was followed in analyzing the chromosomes of parents and sibs of patients found to have a chromosomal abnormality. A few metaphase plates from each case were re-examined independently by Dr. E. T h e r m a n Patau. No case was decoded until a final conclusion had been reached regarding the analysis. If a chromosomal abnormality was established, the case was decoded immediately, in order to facilitate prompt follow-up studies of the patients and their families. In all other cases, decoding was delayed until all 20 analyses had been completed. CASE REPORTS
AND RESULTS
For the sake of brevity, only historical items of special interest are mentioned. For cytologic results and some other information, see Table I. The 8 patients had a total of 18 sibs. Twelve sibs available for chromosome analysis had normal karyotypes. Case 1 (TS310352). The patient, a Caucasian male, had lethargy and feeding difficulty in infancy. He walked at two years, and he communicates mainly by gesture. Binet score was 35. Physical abnormalities. Abnormalities included hypoplasia of the left face, flattening of the superior helix of the right ear, a few Brushfield spots bilaterally, bilateral simian creases, clinodactyly of the fifth fingers, 50 per cent syndactyly of the right index and third fingers, metatarsus adduetus, 50 per cent syndactyly of the second and third toes bilaterally, a hypoplastic penis and scrotum, anterior phimosis, dorsal kyphosis, a sacral dimple, hyperextensible joints, and a large car6 au lait spot over the left scapula. Cytologic diagnosis. The diagnosis was 46,XY, Dpt. In all modal cells only 5 chromosomes of the D group could be iden@ed; all contained 16 chromosomes apparently i~elonging to the C group. Evidently the patient is partially trisomlc for a segment translocated to the short arm of a D chromosome from an unknown donor chromosome. The translocation chromosome is
446
Daly
The Journal o[ Pediatrics September 1970
Table I
Case Age ~ No__...m~ (yr.) 1 2 3 4 5 6
111a/~. 10 7A2 7la/az 5 ~2 101~ 10~/J2
7 8
17 }12 6
9
24
~
Chromosome constitution
No. o[ cells analyzed
I
46,XY, (Dpt) +:~ 46,XX, (Dpt)+ 46,XX,Cq46,XY, Bp46,XY,t ( 16q+;Cq-) 45,XY,D--,t ( DqDq ) + 46,XY,17ps 46,XY 47,XXX 45,X 46,XY 47,XXY
16
11 11 11 11 11 7 23 11 33 51 2
Parental age at b i r t h
I
Carrier of chromosome abnormality Father
1 0 0 0 0 0
38 24 38 30 20 25
37 26 38 33 20 26
No No No No No No
DqDq
0 0
34 22
31 30
No No
No ?
?
?
4
Unknown
No No No No
SAt time of examination. "~Only cells with at least 44 chromosomes, ~Nomenclature recommended by Chicago Conference. as
indistinguishable from the C chromosomes. Case 2 (SW280754). The patient was a Caucasian female, with a birth weight of 2,300 Gin. She was a lethargic, jaundiced neonate with feeding difficulty. She sat up at one year and walked at 2I~ years. Speech was markedly delayed. Binet score was 46. Physical abnormalities. Abnormalites included trigonocephaly, a few Brushfield spots bilaterally, antimongoloid slant of the eyes, a prominent malar flush, a probable small ventricular septal defect, bilateral splayfoot, hammer toes, and genu valgum. Cytologic diagnosis. The diagnosis was 46,XX, Dpt. In all cells only 5 chromosomes of the D group could be identified; all contained 16 chromosomes appearing to belong to the C group (Fig. 1). Comments. T h e karyotypes of these two patients are distinguishable only because of the sex chromosome complements, but in each case the abnormal chromosome h a d arisen de novo, since neither of the parents was a carrier. If the clinical conditions in Cases 1 and 2 are the result of the observed chromosomal aberration, they would have to be considered to be caused by partial trisomy for the material translocated to the D's, since the concomitant .loss of some of the short a r m of the D's would almost certainly be innocuous. T h e marked differences in the two phenotypes indicates, not surprisingly, that the translocated chromosome
pieces were of different origin. Although Case 1 has a few of the anomalies found in the G1 and D1 trisomies, the total clinical picture in neither case is reminiscent of these syndromes. I have not found in the literature any other phenotypes sufficiently similar to either patient to provide clues regarding the source of the chromosome material translocated to the D chromosome. Case 3 (MO310354). This patient, a Caucasian female, had nasal regurgitation during the first year. She sat up at one year and walked at 2 years. Speech was markedly delayed: I.Q. equivalent was 21. Physical abnormalities. Abnormalities included brachycephaly, hypertelorism, antimongoloid slant of the. eyes, epicanthal folds, strabismus, macrostomia, and downward slant of angles of the mouth. Cytologic diagnosis. The diagnosis was 46,XX, Cq-. Each cell contained only 15 chromosomes which appeared to belong to the C group and 1 chromosome which could not be distinguished with certainty from No. 16, and obviously had come about by loss of chromosome material from the long arm of a C (Fig. 2). Although many cells from a fibroblast culture were not of the best quality, several analyzable cells were found to have the same karyotype. Comments. Deletion of part of the long a r m of an X chromosome is a possible but unlikely interpretation of this a b n o r m a l karyotype. We do not have additional cyto-
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Chromosome aberrations in mental retardates
44 7
Fig. 1. Karyotype of Case 2, showing 5 D chromosomes and 17 apparent C chromosomes.
Fig. 2. Karyotype of Case 3, showing 15 C chromosomes and 3 chromosomes with the appearance of chromosome 16. logic evidence for or against this possibility because an attempt to label the fibroblast culture with radioactive thymidine was not successful, and the original buccal smear was unsatisfactory. This patient needs to be forcibly restrained for even the simplest procedure. H e r parents are not willing to have
additional studies done at this time. Jacobs and associates, ~ de Grouchy and associates, 4 and Ferguson-Smith and associate# have noted that only short stature, disturbed menstruation, and "streak gonads" characterized the female patients reported to have a long alan deletion of the X chromosome. They
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DaIy
The Journal oI Pediatrics September 1970
tardation was obvious before meningitis at 11 months. He walked at 4.5 years; there was no meaningful speech. Physical abnormalities. Abnormalities included microcephaly, narrow palpebral fissures, a right upper epicanthal fold, a narrow palate, bilateral simian creases, and hypotonic musculature (Fig. 3). Cytologic diagnosis. The diagnosis was 46,XY, Bp-. In all ceils one B chromosome had a deletion of a portion of the short arms (Fig. 4). Comments. This patient obviously has the cri du chat syndrome and would not have been included in the study had this been known, but his record did not contain the history of a catlike cry. A survey of the published photographs of such children reveals that with advancing age, the physiognomy becomes less helpful as an aid in diagnosing the syndrome. At age 54/12 years, he did not have the moonlike face of infants with the eri du chat syndrome.
Fig. 3. Case 4. have neither the severe mental defect nor the other abnormalities described in our patient. Migeon 6 has reported on a mentally retarded girl with multiple anomalies quite different from those of our Patient; labeling with radioactive thymidine showed that the C chromosome with a long arm deletion is not an X chromosome. Biseatti 7 described a young glrl with mental retardation and several minor anomalies whose karyotype appears similar but whose physical characteristics do not resemble those of our patient; the author h a d no additional cytologic evidence for determining whether an X chromosome was affected. I t seems that the partially deleted C chromosome in the present case was an autosome, possibly one for which a deletion has not yet been described. Further studies on this patient are intended. Case 4 (DN301260). Case 4, a Caucasian male, as a neonate had catlike cry (unknown to us at time of examination). Psychomotor re-
Case 5 (RB030155). This infant, a Caucasian male, had markedly delayed speech. Physical abnormalities. Abnormalities included a low anterior hairline, synophrys, a preauricular sinus, a narrow anterior palate, strabismus, right ptosis, bilateral clinodactyly, and distal axial triradii. Cytologic diagnosis. The diagnosis was 46,XY, t(16q+;Cq-). Each cell contained one No. 16 chromosome whose long arms were of greater mass than those of the homologue. Although the material was not of ideal quality, several cells clearly had a metacentric C chromosome; a check of many additional cells indicated that this was present in all cells (Fig. 5). Comments. This patient balanced translocation. If somal aberration could not his physical anomalies and tion.
seems to have a so, the chromobe the cause of mental retarda-
Case 6 (DR291154). This Caucasian male had projectile vomiting in infancy and markedly delayed speech. Binet score was 57. Physical abnormalities. Abnormalities included asymmetrical ears with right-angled helix on the right, a flat occiput, hemangioma over the midforehead, synophrys, a high-arched palate, exaggerated lumbar lordosis, lower thoracic scoliosis,
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Chromosome aberrations in mental retardates
4 49
Fig. 4. Karyotype of Case 4, showing deletion of part of the short arm of a chromosome 5.
Fig. 5. Karyotype of Case 5, showing a balance transloeation between a C chromosome and a chromosome No. 16.
a large brown nevus over the left scapula, a gynecoid pelvis, an undescended right testicle, a right inguinal hernia, a hypoplastic penis, and hypoplastic nipples. Cytologic diagnosis. The diagnosis was 46,XY, D-,t(DqDq)+. Only 4 D chromosomes could be
identified. A metacentric chromosome, closely resembling the No. 3 chromoso~e, was present in all cells (Fig. 6). C o m m e n t s . Since the physically a n d m e n tally n o r m a l father of this boy carries the
4 50
Daly
The lournal o[ Pediatrics September 1970
Fig. 6. Karyotype of Case 6, showing the DqDq translocation.
same translocation, it is certain that the centric fusion translocation is between nonhomologous D chromosomes. Considering the relatively high frequency of this type of D q D q translocation in m a n (about one in 1,000 of the general population, according to C o u r t BrownS), and the absence of any recurring group of phenotypic traits a m o n g the translocation heterozygotes identified so far, it is most probable that the translocation in this boy is not the cause of his physical and mental defects. Recently a control individual in the Madison Blind Study was also found to have a nonhomologous D q D q translocation (Doyle~ Case 7 (JE281147). This Caucasian male was a dizygotic twin with a birth weight of 2,414 Gm. He walked at 21 months and had markedly delayed speech. Binet score was 57. Physical abnormalities. Abnormalities included brachycephaly, a low posterior hairline, anteverted ears, bilateral ptosis, trace of webbing of the neck, a depressed sternum, diastasis recti, small areolae, hypoplastic nipples, right inguinal hernia, distal axial triradii, syndactyly of the left second and third toes, and clinodactyly of the left fifth finger (Fig. 7). Cytologic diagnosis. The diagnosis was 46,XY, 17ps. The satellite at the short arm of a chromo-
some No. 17 was large compared with the usual satellites of human acrocentrics and need not represent extra material (Fig. 8). Rather, it may have resulted from the appearance of a new secondary constriction. In most cells, the satellite could not be recognized, but this may have been a variable manifestation of the secondary constriction rather than true mosaicism. An attempted skin culture did not succeed. Comments. Satellites on chromosome No. 17 have been reported in phenotypically normal individuals, including a control individual in the Madison Blind S t u d y (Doyleg), as well as in those with physical abnormalities; in the latter cases, the association of the physical defects and this chromosomal aberration m a y be simply fortuitous (for example, see Atnip and Summitt, l~ Emerit and associates, 11 Moores and associates, 12 Jacobs, la and German1*). Case 8 (NM141058). This patient, a Caucasian female, had a "buffalo hump," "claw hands," and inverted feet noted at birth. Speech was markedly delayed. Physical abnormalities. Abnormalities included frontal bossing, a high narow forehead, antimongoloid slant of the eyes, mild prognathism, hypertelorism, eversion of the lips, partial flexion
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Chromosome aberrations in mental retardates
45 1
severe mental retardation and multiple anomalies. However, the patient's face was reminiscent of the Franceschetti syndrome, and there were marked deformities of the thorax. In general, physical abnormalities are not regular features of the triplo-X condition as it is understood currently. Case 9 (FC140931). The patient, a Caucasian male university student, was married and the father of two children. Cytologic diagnosis. The diagnosis was 45,X/46,xY/a7,xxY. Comments. I t is not surprising that the very small proportion of 47,XXY cells, presumably resulting from mitotic nondisjunction, have not affected the patient's phenotype. T h e 45,X cell line found in 38.4 per cent of his peripheral lymphocytes m a y be m u c h more rare or even absent in other tissues. DISCUSSION
Fig. 7. Case 7.
of the distal phalanges of the hands, and pronation of the feet with lack of ability to extend the proximal interphalangeal joints. Cytologic diagnosis. The diagnosis was 47, XXX. Eleven analyzed cells contained 47 chromosomes. The additional chromosome belonged to t h e C group. In a buccal smear no Barr bodies were found in 42 cells, one in 27, and two in 31. Comments. This patient was ascertained because of having multiple anomalies plus mental retardation. Gilgenkrantz and associates 15 described a triplo-X female with
Phenotypically normal individuals may carry visible structural abnormalities of chromosomes which are of two types: (1) those leaving the genetic balance undisturbed and (2) those involving a deletion of or addition to the normal amount of chromosome material that does not alter the genetic balance sufficiently to cause clinical abnormalities. In this study, cases of both types have been found. T h e first type is typically represented by a reciprocal translocation in which the two abnormal chromosomes compensate for each other. Although it cannot be proved beyond doubt that Case 5, diagnosed as 46,XY, t ( 1 6 q + ; C q - ) , is of this kind, this is the most probable assumption. The cytogenetic literature is replete with examples of this type of rearrangement. In contradistinction to our patient, such translocation carriers are usually ascertained through an afflicted relative who is abnormM because of the presence of only one of the translocation chromosomes. I t is possible that Case 7, the patient with satellites one'chromosome No. 17, also belongs to this type insofar as the new secondary constriction might conceivably be a structural alteration not in-
452
Daly
The Journal o[ Pediatrics September 1970
Fig. 8. E group chromosomes from 4 cells, showing satellites on one chromosome No. 17 in Case 7.
volving genetic material. However, this patient might also belong to the second type. The second type of chromosomal abnormality exists in Case 6, the boy carrying a centric fusion of nonhomologous D chromosomes. In the formation of this type of translocation, a small chromosome composed mainly or exclusively of short arm material is also produced and is usually lost in a subsequent cell division. It is certainly absent in the cells of the present patient as it is in his father, presumably without clinical consequences. DqDq translocation carriers may of course produce chromosomally grossly imbalanced progeny, but according to Hamerton ~s this seems to be quite rare. It is gratifying that in the present series, as in the other samples of the Madison Blind Study, structural aberrations which might be expected to cause serious genetic imbalance were found exclusively among the patient group. This sample is obviously too small to give a meaningful estimate of the over-all incidence of either deleterious or innocuous chromosomal abnormalities in the patient or control populations. The drawing of statistical inferences must be left to the common analysi s of a sufficient number
of such samples. For a first report on pooled data from the Madison Blind Study see Patau. 17 SUMMARY
Fifty mentally retarded patients with three or more other anomalies were compared with 50 normal control subjects by analysis of chromosomes using coded, randomized slides. Patients recognized as having a known syndrome were excluded. This series is a portion of a long-range, continuing study designed to give information on the incidenc.e of chromosomal abnormalities among this class of patients and control subjects. Of 8 retarded patients with a chromosomal abnormality, 7 have a structural aberration; the other is triplo-X. One abnormality, mosaicism involving the sex chromosomes, was found in a control subject. In three cases, the structural chromosomal abnormality is probably not causative of the patient's physical and mental defects. Such variants occur in otherwise normal people, but their relative frequencies in the general population and in selected patient groups are undetermined. Statistical inferences relating tO such problems can be made from larger data accruing in the Madison study.
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Chromosome aberrations in mental retardates
I wish to thank Dr. Klaus Patau for his planning and supervision of this work and Dr. E. Therman Patau for very generous assistance. I am indebted to Dr. John Opitz for providing many of the cases studied, to Dr. Virginia Dowries, former superintendent of the Bureau of Maternal and Child Health, Milwaukee Health Department, and to the many physicians in that bureau whose cooperation made this study possible.
8. 9. 10.
tl.
REFERENCES 1. Summitt, R. L.: Cytogenetics in mentally defective children with anomalies: A controlled study, J. P~mAT. 74: 58, 1969. 2. Moorhead, P. S., Nowell, P. C., Mellman, W. J., Battips, D. M., and Hungerford, D. A.: Chromosome preparations of leucocyte cultures from human peripheral blood, J. Exp. Cell Res. 20: 613, 1960. 3. Jacobs, P. A., Harnden, D. G., Court Brown, W. M., Goldstein, J., Close, H. G., MacGregor, T. N., Maclean, N., and Strong, J. A.: Abnormalities involving the X chromosome in women, Lancet 1: 1213, 1960. 4. de Grouchy, J., Lamy, M., Yaneva, H., Salomon, Y., and Netter, A.: Further abnormalities of the X chromosome in primary amenorrhoea or in severe oligomenorrhoea, Lancet 2: 777, 1961. 5. Ferguson-Smith, M. A., Alexander, D. S., Bowen, P., Goodman, R. M., Kaufmann, B. N., Jones, H. W., and Holler, R. H.: Clinical and cytogenetical studies in female gonadal dysgenesis and their bearing on the cause of Turner's syndrome, Cytogenetics 3: 355, 1964. 6. Migeon, B. R.: Personal communication. 7. Biscatti, G.: Parziale delezione delle braccla
12.
13.
14. 15.
16. 17.
18.
453
lunghe di un cromosoma del gruppo 6-12, Pediatria (Napoli) 73: 660, 1965. Court Brown, W. M.: Human population cytogenetics, Amsterdam, 1967, North Holland Publishing Company. Doyle, C. : Personal communication. Atnip, R. L., and Summitt, R. L.: Chromosomal abnormalities in mentally defective children with other anomalies and in normal adult control subjects (Abst.), Amer. Soc. Hum. Goner. 54, 1967. Emerit, I., de Grouchy, J., Varnant, P., and Corone, P.: Chromosomal abnormalities and congenital heart disease, Circulation 36: 886, 1967. Moores, E. C., Anders, J. M., and Emanuel, R.: Inheritance of marker chromosomes from a cytogenetic survey of congenital heart disease, Ann. Hum. Genet. 30: 77, 1966. Jacobs, P. A.: Chromosome studies in the general population, in Harris, R. J. C., editor: Cytogenetics of cells in culture, New York, 1964, Academic Press, Inc., pp. 111121. German, J.: The chromosomal structural load in man, Texas Rep. Biol. Med. 24: 348, 1966. Gilgenkrantz, S., Gilgenkrantz, J.-M. Streiff, F., Fauchier, J.-P., and Baillon, D.: Syndrome triplo-X et anomalies squelettiques, Ann. Med. Nancy 6: 172, 1967. Hamerton, J. L.: Robertsonian translocations in man; evidence for prezygotic selection, Cytogenetics 7: 260, 1968. Patau, K.: Chromosome abnormalities in normals and in idiopathic mental retardates with multiple anomalies, (Abst.), Twelfth Int. Cong. Genet. 212, 1968. Chicago Conference: Standardization in Human Cytogenetics, Birth Defects: Original Article Series II: 2, 1966, New York, The National Foundation.
444
The ]ournal of P E D I A T R I C S
Chromosome aberrations in 50 patients Mtb idiopathic mental retardation and in 50 control subjects Madison Blind Study III Analysis of coded, randomized chromosome preparations from 50 mentally retarded patients with three or more anomalies and from 50 normal control subjects revealed chromosomal abnormalities among 8 patients. Seven of these have changes in chromosome structure; the other is triplo-X. In 3 patients the structural abnormality is probably unrelated to the physical and mental defects. One control subject has mosaicism involving sex chromosomes.
Richard F . Daly, M.D. MADISON,
WIS.
S O M E V A R I A T I O N Of chromosomal structure occurs even among apparently normal persons. If, by coincidence, a variant is present in a retarded individual with multiple congenital anomalies, it may be interpreted incorrectly as the cause of his defects. For certain types of chromosome variants, only an extended comparative study of such patients and healthy control subjects can establish whether these variants have serious consequences. Such a study would also help to determine for what fraction of mentally retarded patients whose conditions do not represent a known syndrome a chromosomal causation can be assumed. The present report describes part of a From the University of Wisconsin. Supported by Grant GM-15422 from the National Institutes of Health to Dr. K. Patau. Address: UMvers~ty of Wisconsin, 515 Genetics Building, Madison, Wi$. 53706. Vol. 77, No. 3, pp. 444-453
long-range, continuing study* designed by Prof. Klaus Patau to give information on the incidence of chromosomal abnormalities among a certain class of patients and control subjects. Several participants have analyzed chromosomes (on coded slides) from individuals selected because they had mental retardation combined with at least 3 other anomalies and from an equal number of control subjects. Patients diagnosed as having a known syndrome were excluded. Apart from the very rare instances of diploid-triploid mosaicism, chromosomal aberrations found in live persons belong to either of two classes. One is aneuploidy sensu strictu, i.e., a wrong number of one or a few of the normal chromosomes; the other consists of structural abnormalities of chromosomes. All or most of the viable types of aneuploidy are known. Since the great * F o r parts I a n d I I see S u m m l t t ~ a n d P a t a u . ~T
Volume 77 Number 3
Chromosome aberrations in mental retardates
majority of such types, in particular the 3 autosomal trisomies, can be diagnosed clinically, few would get into the present study, unless mosaicism rendered the clinical expression atypical. It could therefore be anticipated that in the present group of patients chromosome abnormalities would often be of the structural kind. Since the number of chromosomes in this group is more often than not normal, the microscopic detection of such aberrations can be difficult or often even impossible. Since bias in interpreting the cytologic findings is a real danger, it is essential that any comparative study such as the present one be conducted blindly. MATERIAL
AND
METHODS
The group described is composed of 50 mentally retarded patients who have at least 3 other anomalies and 50 phenotypically normal control subjects. T h e rationale for establishing the criteria for patient selection is given by Summitt 1 in a recent description of his findings in a portion of this study. Most of the patients were chosen from special classes for retarded children in the Milwaukee school system. Screening of patients to find those meeting the criteria was done by the school physicians, members of the Milwaukee Health Department. T h e remainder were obtained from the Pediatrics Department, University Hospitals, University of Wisconsin, and from the Central Wisconsin Colony and Training School. Either Dr. John Opitz or I made the final selection of patients. Members of the staff and students at the University of Wisconsin served as control subjects. Chromosome preparations were made from the lymphocytes of 10 ml. of venous blood using a slight modification of the technique described by Moorhead and associates. 2 Two slides from each culture were stained with one per cent aceto-orcein, 2 with Feulgen (omitting the SOs washings), and 2 with azur A. Each individual was assigned a code number so that 20 consecutive numbers represented 10 patients and 10 control subjects in a random sequence. All metaphase plates studied were selected for good tech-
445
nical quality and analyzed at the microscope as completely as possible by means of pencil sketches. T h e scheme for determining the number of cells to be analyzed in each case is a routine followed in the blind study and has been described by Summitt. 1 The same procedure was followed in analyzing the chromosomes of parents and sibs of patients found to have a chromosomal abnormality. A few metaphase plates from each case were re-examined independently by Dr. E. T h e r m a n Patau. No case was decoded until a final conclusion had been reached regarding the analysis. If a chromosomal abnormality was established, the case was decoded immediately, in order to facilitate prompt follow-up studies of the patients and their families. In all other cases, decoding was delayed until all 20 analyses had been completed. CASE REPORTS
AND RESULTS
For the sake of brevity, only historical items of special interest are mentioned. For cytologic results and some other information, see Table I. The 8 patients had a total of 18 sibs. Twelve sibs available for chromosome analysis had normal karyotypes. Case 1 (TS310352). The patient, a Caucasian male, had lethargy and feeding difficulty in infancy. He walked at two years, and he communicates mainly by gesture. Binet score was 35. Physical abnormalities. Abnormalities included hypoplasia of the left face, flattening of the superior helix of the right ear, a few Brushfield spots bilaterally, bilateral simian creases, clinodactyly of the fifth fingers, 50 per cent syndactyly of the right index and third fingers, metatarsus adduetus, 50 per cent syndactyly of the second and third toes bilaterally, a hypoplastic penis and scrotum, anterior phimosis, dorsal kyphosis, a sacral dimple, hyperextensible joints, and a large car6 au lait spot over the left scapula. Cytologic diagnosis. The diagnosis was 46,XY, Dpt. In all modal cells only 5 chromosomes of the D group could be iden@ed; all contained 16 chromosomes apparently i~elonging to the C group. Evidently the patient is partially trisomlc for a segment translocated to the short arm of a D chromosome from an unknown donor chromosome. The translocation chromosome is
446
Daly
The Journal o[ Pediatrics September 1970
Table I
Case Age ~ No__...m~ (yr.) 1 2 3 4 5 6
111a/~. 10 7A2 7la/az 5 ~2 101~ 10~/J2
7 8
17 }12 6
9
24
~
Chromosome constitution
No. o[ cells analyzed
I
46,XY, (Dpt) +:~ 46,XX, (Dpt)+ 46,XX,Cq46,XY, Bp46,XY,t ( 16q+;Cq-) 45,XY,D--,t ( DqDq ) + 46,XY,17ps 46,XY 47,XXX 45,X 46,XY 47,XXY
16
11 11 11 11 11 7 23 11 33 51 2
Parental age at b i r t h
I
Carrier of chromosome abnormality Father
1 0 0 0 0 0
38 24 38 30 20 25
37 26 38 33 20 26
No No No No No No
DqDq
0 0
34 22
31 30
No No
No ?
?
?
4
Unknown
No No No No
SAt time of examination. "~Only cells with at least 44 chromosomes, ~Nomenclature recommended by Chicago Conference. as
indistinguishable from the C chromosomes. Case 2 (SW280754). The patient was a Caucasian female, with a birth weight of 2,300 Gin. She was a lethargic, jaundiced neonate with feeding difficulty. She sat up at one year and walked at 2I~ years. Speech was markedly delayed. Binet score was 46. Physical abnormalities. Abnormalites included trigonocephaly, a few Brushfield spots bilaterally, antimongoloid slant of the eyes, a prominent malar flush, a probable small ventricular septal defect, bilateral splayfoot, hammer toes, and genu valgum. Cytologic diagnosis. The diagnosis was 46,XX, Dpt. In all cells only 5 chromosomes of the D group could be identified; all contained 16 chromosomes appearing to belong to the C group (Fig. 1). Comments. T h e karyotypes of these two patients are distinguishable only because of the sex chromosome complements, but in each case the abnormal chromosome h a d arisen de novo, since neither of the parents was a carrier. If the clinical conditions in Cases 1 and 2 are the result of the observed chromosomal aberration, they would have to be considered to be caused by partial trisomy for the material translocated to the D's, since the concomitant .loss of some of the short a r m of the D's would almost certainly be innocuous. T h e marked differences in the two phenotypes indicates, not surprisingly, that the translocated chromosome
pieces were of different origin. Although Case 1 has a few of the anomalies found in the G1 and D1 trisomies, the total clinical picture in neither case is reminiscent of these syndromes. I have not found in the literature any other phenotypes sufficiently similar to either patient to provide clues regarding the source of the chromosome material translocated to the D chromosome. Case 3 (MO310354). This patient, a Caucasian female, had nasal regurgitation during the first year. She sat up at one year and walked at 2 years. Speech was markedly delayed: I.Q. equivalent was 21. Physical abnormalities. Abnormalities included brachycephaly, hypertelorism, antimongoloid slant of the. eyes, epicanthal folds, strabismus, macrostomia, and downward slant of angles of the mouth. Cytologic diagnosis. The diagnosis was 46,XX, Cq-. Each cell contained only 15 chromosomes which appeared to belong to the C group and 1 chromosome which could not be distinguished with certainty from No. 16, and obviously had come about by loss of chromosome material from the long arm of a C (Fig. 2). Although many cells from a fibroblast culture were not of the best quality, several analyzable cells were found to have the same karyotype. Comments. Deletion of part of the long a r m of an X chromosome is a possible but unlikely interpretation of this a b n o r m a l karyotype. We do not have additional cyto-
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Fig. 1. Karyotype of Case 2, showing 5 D chromosomes and 17 apparent C chromosomes.
Fig. 2. Karyotype of Case 3, showing 15 C chromosomes and 3 chromosomes with the appearance of chromosome 16. logic evidence for or against this possibility because an attempt to label the fibroblast culture with radioactive thymidine was not successful, and the original buccal smear was unsatisfactory. This patient needs to be forcibly restrained for even the simplest procedure. H e r parents are not willing to have
additional studies done at this time. Jacobs and associates, ~ de Grouchy and associates, 4 and Ferguson-Smith and associate# have noted that only short stature, disturbed menstruation, and "streak gonads" characterized the female patients reported to have a long alan deletion of the X chromosome. They
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tardation was obvious before meningitis at 11 months. He walked at 4.5 years; there was no meaningful speech. Physical abnormalities. Abnormalities included microcephaly, narrow palpebral fissures, a right upper epicanthal fold, a narrow palate, bilateral simian creases, and hypotonic musculature (Fig. 3). Cytologic diagnosis. The diagnosis was 46,XY, Bp-. In all ceils one B chromosome had a deletion of a portion of the short arms (Fig. 4). Comments. This patient obviously has the cri du chat syndrome and would not have been included in the study had this been known, but his record did not contain the history of a catlike cry. A survey of the published photographs of such children reveals that with advancing age, the physiognomy becomes less helpful as an aid in diagnosing the syndrome. At age 54/12 years, he did not have the moonlike face of infants with the eri du chat syndrome.
Fig. 3. Case 4. have neither the severe mental defect nor the other abnormalities described in our patient. Migeon 6 has reported on a mentally retarded girl with multiple anomalies quite different from those of our Patient; labeling with radioactive thymidine showed that the C chromosome with a long arm deletion is not an X chromosome. Biseatti 7 described a young glrl with mental retardation and several minor anomalies whose karyotype appears similar but whose physical characteristics do not resemble those of our patient; the author h a d no additional cytologic evidence for determining whether an X chromosome was affected. I t seems that the partially deleted C chromosome in the present case was an autosome, possibly one for which a deletion has not yet been described. Further studies on this patient are intended. Case 4 (DN301260). Case 4, a Caucasian male, as a neonate had catlike cry (unknown to us at time of examination). Psychomotor re-
Case 5 (RB030155). This infant, a Caucasian male, had markedly delayed speech. Physical abnormalities. Abnormalities included a low anterior hairline, synophrys, a preauricular sinus, a narrow anterior palate, strabismus, right ptosis, bilateral clinodactyly, and distal axial triradii. Cytologic diagnosis. The diagnosis was 46,XY, t(16q+;Cq-). Each cell contained one No. 16 chromosome whose long arms were of greater mass than those of the homologue. Although the material was not of ideal quality, several cells clearly had a metacentric C chromosome; a check of many additional cells indicated that this was present in all cells (Fig. 5). Comments. This patient balanced translocation. If somal aberration could not his physical anomalies and tion.
seems to have a so, the chromobe the cause of mental retarda-
Case 6 (DR291154). This Caucasian male had projectile vomiting in infancy and markedly delayed speech. Binet score was 57. Physical abnormalities. Abnormalities included asymmetrical ears with right-angled helix on the right, a flat occiput, hemangioma over the midforehead, synophrys, a high-arched palate, exaggerated lumbar lordosis, lower thoracic scoliosis,
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Fig. 4. Karyotype of Case 4, showing deletion of part of the short arm of a chromosome 5.
Fig. 5. Karyotype of Case 5, showing a balance transloeation between a C chromosome and a chromosome No. 16.
a large brown nevus over the left scapula, a gynecoid pelvis, an undescended right testicle, a right inguinal hernia, a hypoplastic penis, and hypoplastic nipples. Cytologic diagnosis. The diagnosis was 46,XY, D-,t(DqDq)+. Only 4 D chromosomes could be
identified. A metacentric chromosome, closely resembling the No. 3 chromoso~e, was present in all cells (Fig. 6). C o m m e n t s . Since the physically a n d m e n tally n o r m a l father of this boy carries the
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Fig. 6. Karyotype of Case 6, showing the DqDq translocation.
same translocation, it is certain that the centric fusion translocation is between nonhomologous D chromosomes. Considering the relatively high frequency of this type of D q D q translocation in m a n (about one in 1,000 of the general population, according to C o u r t BrownS), and the absence of any recurring group of phenotypic traits a m o n g the translocation heterozygotes identified so far, it is most probable that the translocation in this boy is not the cause of his physical and mental defects. Recently a control individual in the Madison Blind Study was also found to have a nonhomologous D q D q translocation (Doyle~ Case 7 (JE281147). This Caucasian male was a dizygotic twin with a birth weight of 2,414 Gm. He walked at 21 months and had markedly delayed speech. Binet score was 57. Physical abnormalities. Abnormalities included brachycephaly, a low posterior hairline, anteverted ears, bilateral ptosis, trace of webbing of the neck, a depressed sternum, diastasis recti, small areolae, hypoplastic nipples, right inguinal hernia, distal axial triradii, syndactyly of the left second and third toes, and clinodactyly of the left fifth finger (Fig. 7). Cytologic diagnosis. The diagnosis was 46,XY, 17ps. The satellite at the short arm of a chromo-
some No. 17 was large compared with the usual satellites of human acrocentrics and need not represent extra material (Fig. 8). Rather, it may have resulted from the appearance of a new secondary constriction. In most cells, the satellite could not be recognized, but this may have been a variable manifestation of the secondary constriction rather than true mosaicism. An attempted skin culture did not succeed. Comments. Satellites on chromosome No. 17 have been reported in phenotypically normal individuals, including a control individual in the Madison Blind S t u d y (Doyleg), as well as in those with physical abnormalities; in the latter cases, the association of the physical defects and this chromosomal aberration m a y be simply fortuitous (for example, see Atnip and Summitt, l~ Emerit and associates, 11 Moores and associates, 12 Jacobs, la and German1*). Case 8 (NM141058). This patient, a Caucasian female, had a "buffalo hump," "claw hands," and inverted feet noted at birth. Speech was markedly delayed. Physical abnormalities. Abnormalities included frontal bossing, a high narow forehead, antimongoloid slant of the eyes, mild prognathism, hypertelorism, eversion of the lips, partial flexion
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severe mental retardation and multiple anomalies. However, the patient's face was reminiscent of the Franceschetti syndrome, and there were marked deformities of the thorax. In general, physical abnormalities are not regular features of the triplo-X condition as it is understood currently. Case 9 (FC140931). The patient, a Caucasian male university student, was married and the father of two children. Cytologic diagnosis. The diagnosis was 45,X/46,xY/a7,xxY. Comments. I t is not surprising that the very small proportion of 47,XXY cells, presumably resulting from mitotic nondisjunction, have not affected the patient's phenotype. T h e 45,X cell line found in 38.4 per cent of his peripheral lymphocytes m a y be m u c h more rare or even absent in other tissues. DISCUSSION
Fig. 7. Case 7.
of the distal phalanges of the hands, and pronation of the feet with lack of ability to extend the proximal interphalangeal joints. Cytologic diagnosis. The diagnosis was 47, XXX. Eleven analyzed cells contained 47 chromosomes. The additional chromosome belonged to t h e C group. In a buccal smear no Barr bodies were found in 42 cells, one in 27, and two in 31. Comments. This patient was ascertained because of having multiple anomalies plus mental retardation. Gilgenkrantz and associates 15 described a triplo-X female with
Phenotypically normal individuals may carry visible structural abnormalities of chromosomes which are of two types: (1) those leaving the genetic balance undisturbed and (2) those involving a deletion of or addition to the normal amount of chromosome material that does not alter the genetic balance sufficiently to cause clinical abnormalities. In this study, cases of both types have been found. T h e first type is typically represented by a reciprocal translocation in which the two abnormal chromosomes compensate for each other. Although it cannot be proved beyond doubt that Case 5, diagnosed as 46,XY, t ( 1 6 q + ; C q - ) , is of this kind, this is the most probable assumption. The cytogenetic literature is replete with examples of this type of rearrangement. In contradistinction to our patient, such translocation carriers are usually ascertained through an afflicted relative who is abnormM because of the presence of only one of the translocation chromosomes. I t is possible that Case 7, the patient with satellites one'chromosome No. 17, also belongs to this type insofar as the new secondary constriction might conceivably be a structural alteration not in-
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Fig. 8. E group chromosomes from 4 cells, showing satellites on one chromosome No. 17 in Case 7.
volving genetic material. However, this patient might also belong to the second type. The second type of chromosomal abnormality exists in Case 6, the boy carrying a centric fusion of nonhomologous D chromosomes. In the formation of this type of translocation, a small chromosome composed mainly or exclusively of short arm material is also produced and is usually lost in a subsequent cell division. It is certainly absent in the cells of the present patient as it is in his father, presumably without clinical consequences. DqDq translocation carriers may of course produce chromosomally grossly imbalanced progeny, but according to Hamerton ~s this seems to be quite rare. It is gratifying that in the present series, as in the other samples of the Madison Blind Study, structural aberrations which might be expected to cause serious genetic imbalance were found exclusively among the patient group. This sample is obviously too small to give a meaningful estimate of the over-all incidence of either deleterious or innocuous chromosomal abnormalities in the patient or control populations. The drawing of statistical inferences must be left to the common analysi s of a sufficient number
of such samples. For a first report on pooled data from the Madison Blind Study see Patau. 17 SUMMARY
Fifty mentally retarded patients with three or more other anomalies were compared with 50 normal control subjects by analysis of chromosomes using coded, randomized slides. Patients recognized as having a known syndrome were excluded. This series is a portion of a long-range, continuing study designed to give information on the incidenc.e of chromosomal abnormalities among this class of patients and control subjects. Of 8 retarded patients with a chromosomal abnormality, 7 have a structural aberration; the other is triplo-X. One abnormality, mosaicism involving the sex chromosomes, was found in a control subject. In three cases, the structural chromosomal abnormality is probably not causative of the patient's physical and mental defects. Such variants occur in otherwise normal people, but their relative frequencies in the general population and in selected patient groups are undetermined. Statistical inferences relating tO such problems can be made from larger data accruing in the Madison study.
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I wish to thank Dr. Klaus Patau for his planning and supervision of this work and Dr. E. Therman Patau for very generous assistance. I am indebted to Dr. John Opitz for providing many of the cases studied, to Dr. Virginia Dowries, former superintendent of the Bureau of Maternal and Child Health, Milwaukee Health Department, and to the many physicians in that bureau whose cooperation made this study possible.
8. 9. 10.
tl.
REFERENCES 1. Summitt, R. L.: Cytogenetics in mentally defective children with anomalies: A controlled study, J. P~mAT. 74: 58, 1969. 2. Moorhead, P. S., Nowell, P. C., Mellman, W. J., Battips, D. M., and Hungerford, D. A.: Chromosome preparations of leucocyte cultures from human peripheral blood, J. Exp. Cell Res. 20: 613, 1960. 3. Jacobs, P. A., Harnden, D. G., Court Brown, W. M., Goldstein, J., Close, H. G., MacGregor, T. N., Maclean, N., and Strong, J. A.: Abnormalities involving the X chromosome in women, Lancet 1: 1213, 1960. 4. de Grouchy, J., Lamy, M., Yaneva, H., Salomon, Y., and Netter, A.: Further abnormalities of the X chromosome in primary amenorrhoea or in severe oligomenorrhoea, Lancet 2: 777, 1961. 5. Ferguson-Smith, M. A., Alexander, D. S., Bowen, P., Goodman, R. M., Kaufmann, B. N., Jones, H. W., and Holler, R. H.: Clinical and cytogenetical studies in female gonadal dysgenesis and their bearing on the cause of Turner's syndrome, Cytogenetics 3: 355, 1964. 6. Migeon, B. R.: Personal communication. 7. Biscatti, G.: Parziale delezione delle braccla
12.
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14. 15.
16. 17.
18.
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lunghe di un cromosoma del gruppo 6-12, Pediatria (Napoli) 73: 660, 1965. Court Brown, W. M.: Human population cytogenetics, Amsterdam, 1967, North Holland Publishing Company. Doyle, C. : Personal communication. Atnip, R. L., and Summitt, R. L.: Chromosomal abnormalities in mentally defective children with other anomalies and in normal adult control subjects (Abst.), Amer. Soc. Hum. Goner. 54, 1967. Emerit, I., de Grouchy, J., Varnant, P., and Corone, P.: Chromosomal abnormalities and congenital heart disease, Circulation 36: 886, 1967. Moores, E. C., Anders, J. M., and Emanuel, R.: Inheritance of marker chromosomes from a cytogenetic survey of congenital heart disease, Ann. Hum. Genet. 30: 77, 1966. Jacobs, P. A.: Chromosome studies in the general population, in Harris, R. J. C., editor: Cytogenetics of cells in culture, New York, 1964, Academic Press, Inc., pp. 111121. German, J.: The chromosomal structural load in man, Texas Rep. Biol. Med. 24: 348, 1966. Gilgenkrantz, S., Gilgenkrantz, J.-M. Streiff, F., Fauchier, J.-P., and Baillon, D.: Syndrome triplo-X et anomalies squelettiques, Ann. Med. Nancy 6: 172, 1967. Hamerton, J. L.: Robertsonian translocations in man; evidence for prezygotic selection, Cytogenetics 7: 260, 1968. Patau, K.: Chromosome abnormalities in normals and in idiopathic mental retardates with multiple anomalies, (Abst.), Twelfth Int. Cong. Genet. 212, 1968. Chicago Conference: Standardization in Human Cytogenetics, Birth Defects: Original Article Series II: 2, 1966, New York, The National Foundation.