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DETECTING MATERNAL CELL CONTAMINATION IN PRENATAL DIAGNOSIS
1074 SUCCESSFUL TREATMENT OF MENINGIOMA WITH OCTREOTIDE
SIR,-Dr Krenning and colleagues (Feb 4, p 242) present a method for tumour localisation with a radioiodinated analogue of somatostatin (tyr-3-octrestide). Among the tumours that could be visualised were meningiomas, in which they had demonstrated somatostatin receptors.’ We report a 30-year-old man in whom a pituitary macroadenoma with intrasellar, parasellar, and suprasellar extension had been diagnosed two years before. The main symptoms were severe headaches which responded only to subcutaneous application of octreotide. The tumour had not been operated on because of an inborn deficiency of coagulation factor XI. Because the patient became tolerant the dosage had to be increased to 500 Ilg thrice daily. For endocrinological evaluation and to exclude possible psychological dependence, octreotide was replaced by subcutaneous injections of normal saline. Normal pituitary function was observed after withdrawal of octreotide and the tumour was shown to be hormonally inactive. However, after three days off octreotide the patient complained of headaches and demanded extra doses of octreotide. Neurological symptoms quickly developed and examination revealed bitemporal visual field defects for the first time; computerised tomographic scanning showed signs of obstructive hydrocephalus. Therefore we resumed the previous medication and 12 hours later headaches had resolved. During the following week visual fields were normal. X-ray after five days showed normal cerebral ventricles and a grossly unchanged tumour
(6 x 4 cm). Because of the need for continued octreotide administration with the development of tolerance, neurosurgical intervention was planned. After substitution of coagulation factors the tumour was subtotally resected. Histological examination of the resected tissue revealed haemangiopericytic meningioma. The patient has been well without octreotide for 4 months now. This outcome suggests favourable acute and chronic effects of octreotide on meningioma size. Scintigraphy with 123I-tyr-3octreotide may be of value in selecting patients with inoperable
somatostatin-receptor-positive meningiomas candidates for octreotide therapy.
as
potential
M. W. RÜNZI
C. JASPERS Departments of Medicine, Neurosurgery, and Neuropathology, University of Essen, 4300 Essen, West Germany
R. WINDECK G. BENKER H. M. MEHDORN V. REINHARDT D. REINWEIN
1. Reubi JC, Maurer R, Klijn JGM, et al. High incidence of somatostatin receptors in human meningiomas: biochemical characterisation. J Clin Endocrinol Metab 1986; 63: 433-38.
free GABA (32 and 25 nmol/1, control range 75-150) and homocamosine (2-5 and 0-9 umol/1, control range 4-10), which are features not previously reported in this condition. The clinical
picture was severe psychomotor retardation, generalised spasticity, and hyperexcitability but no convulsions. Vigabatrin 50 mg/kg per day was started in both children. Within a few days the spasticity and hyperexcitability significantly decreased while CSF GABA levels became normal. The only side-effect was drowsiness in one boy when on a daily dose of 75 mg/kg, but not when he was on 50 mg/kg. These findings suggest that low levels of GABA in the brain could contribute to the symptoms of metachromatic leucodystrophy and that vigabatrin may be a useful treatment for patients with this disease and perhaps other lysosomal disorders. Vigabatrin deserves careful evaluation in primary or secondary GABA metabolism disorders, even when not associated with convulsions. We thank Merrell Dow
(Belgium) for the supply of vigabatrin.
Department of Paediatrics, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
JAAK JAEKEN PAUL CASAER PAUL DE COCK
Dr Willems
Institute, Diepenbeek, Belgium
BAUDOUIN FRANCOIS
1. Pattarelli PP, Nyhan WL, Gibson KM. Oxidation of (U - 14C) succinic semialdehyde in cultured human lymphoblasts: measurement of residual succinic semialdehyde dehydrogenase activity in 11 patients with 4-hydroxybutyric aciduria. Pediatr Res 1988; 24: 455-60. 2. Kolodny EH, Moser HW. Sulfatide lipidosis: metacliromatic leukodystrophy. In. Stanbury JB, Wijngaarden JB, Friedrickson DS, Goldstein JL, Brown MS, eds. The metabolic basis of inherited disease New York: McGraw-Hill, 1983. 881-905.
CHEST DRAIN THROMBECTOMY
SIR,-Blocked chest drains
are not only useless but also reinsertion of drains is difficult, painful, and hazardous, especially after thoracotomy. I have developed a simple technique to unblock chest drains with an arterial embolectomy catheter. This technique is safe, painless, repeatable, and usually successful. Under aseptic conditions a sterile, inflatable, balloon embolectomy catheter is passed proximally along the blocked drain. Intercostal drainage tubes are of a standard length (indicated on the packaging) and embolectomy catheters have a graduated scale; the catheter should be inserted to the limit of the drain only. A catheter with a balloon capacity of 0.75 ml is used. The balloon is inflated with sterile saline and the catheter withdrawn, retrieving the cause of obstruction, which is usually a blood or fibrin clot. Before the inflated balloon is removed from the drain a clamp may be applied to the drain more proximally, until the drain is connected to an underwater system. It is important not to overfill the balloon, which makes withdrawal difficult. This procedure may be repeated as
dangerous, and
accurate
necessary.
VIGABATRIN IN GABA METABOLISM DISORDERS
SiR,—Your March 11editorial focuses on the anticonvulsant properties of vigabatrin, an irreversible inhibitor of GABAaminotransferase, the first step in GABA catabolism. We report our experience with vigabatrin in three children with GABA metabolism disturbances not accompanied by epilepsy. A girl aged 2 years had ataxia and moderate psychomotor retardation due to succinic semialdehyde dehydrogenase deficiency, a defect in the second step of GABA catabolism. This condition is characterised by accumulation of y-hydroxybutyrate in body fluids.’ Vigabatrin 75 mg/kg per day was started in an attempt to reduce y-hydroxybutyrate concentration in the cerebrospinal fluid (CSF); the concentration decreased to 28% of pretreatment value (460 pmol/1) after a month of treatment. CSF free GABA had increased from 95 to 591 nmol/1 (control range for age, 75-150). Ataxia and the electroencephalographic epileptic sharp waves decreased and the improvement has persisted over the 16 months of treatment.
In two other children (boys aged 3 and 7 years) with metachromatic leucodystrophy2 we found decreased lumbar CSF
The technique has been used to salvage drains sited during thoracotomy and drains inserted percutaneously. I am unaware of any complications arising from this technique and it may be
applicable to drains in other sites. University Department of Surgery, General Infirmary at Leeds, Leeds LS1 3EX
R. H. DIAMENT
DETECTING MATERNAL CELL CONTAMINATION IN PRENATAL DIAGNOSIS
StR,—The Canadian multicentre studyl showed that chorionic villus sampling (CVS) is a reliable and accurate sampling procedure for prenatal diagnosis. CVS seems likely to become the prenatal diagnostic procedure of choice for most eligible pregnancies. However, in the Canadian study, maternal cell contamination was recognised in almost 4% of cases even though the trial participants
experienced operators. Furthermore, cytogenetic analysis detected maternal contamination in five cases of male fetuses for every female fetus, suggesting that maternal contamination in as were
1075 biochemical and molecular techniques there may be a serious risk of error. The polymerase chain reaction (PCR) technique is especially prone to error from maternal contamination. For these reasons we suggest that rapid and simple procedures based on hypervariable probes should be introduced into the CVS protocols for DNA diagnoses so that significant maternal contamination can be
recognised. Single locus hypervariable probes are available for the X chromosome and for the pseudoautosomal region common to both X and Y.2-5 Given that the frequencies of individual alleles for such genetic probes are generally less than 5% the probability of distinguishing between mother and fetus, thereby detecting possible maternal contamination, should exceed 99%. Fig 1 illustrates the patterns of restriction fragments that can be expected. We have tested this approach by mixing DNA from a mother and children, to achieve maternal contamination in the range 0-50%,
Fig 1—Possible patterns of restriction fragments indicating ease of detection of maternal contamination in male or female offspring and the identification of XO progeny.
(We thank Yumiko Ishakawa for this diagram.) 80% of the mother/daughter instances would go unrecognised. A 5-10% maternal contamination rate on routine many
as
CVS is probably a realistic expectation, even in good centres. Transabdominal chorionic biopsy is also inseparable from contamination by maternal tissue. When screening for cytogenetic abnormalities this degree of contamination is not too great a problem; however, with
and probing these mixtures with an X chromosome specific and pseudoautosomal probes (fig 2). Simulated maternal contamination can be detected at the 10% level with little difficulty. This application has the advantage that it employs similar procedures to the probe-based diagnostic tests for disease loci. The procedure we suggest has the additional advantage of detecting sex chromosome imbalances; it would also be able to distinguish XO from XY. The development of reagents to allow the extension of this approach to monitor the products from PCR amplification would be highly advantageous. Genetics
Laboratory, Department of Biochemistry, University of Oxford, Oxford OX1 3QU
IAN CRAIG MARK Ross JOHN H. EDWARDS
Murdoch Institute, Melbourne, Australia
NEIL FRASER
Clinical Genetics, University of British Columbia, Vancouver, Canada
JUDITH HALL
1 Canadian Collaborative CVS-amniocentesis Trial
2. 3.
4.
5.
Group. Multicentre randomised clinical trial of clorion villus sampling and amniocentesis. Lancet 1989; i: 1-6. Cooke HJ, Brown WRA, Rappold GA. Hypervariable telomeric sequences from the human sex chromosomes are pseudoautosomal. Nature 1985; 317: 687-91. Davies KE, Mandel J-L, Wiessenbach J, Fellous M. Report of the committee on the genetic constitution of the X- and Y-chromosomes. Cytogenet Cell Genet 1987; 46: 277-315. Fraser NF, Boyd Y, Brownlee G, Craig IW. Multi-allelic RFLP for M27&bgr;, an anonymous single copy genomic clone at Xp 11.3-Xcen. Nucleic Acid Res 1987; 15: 9616 Simmler MC, Johnsson C, Petit C, Rouyer F, Vergnaud G, Weissenbach J. Two highly polymorphic minisatellites from the pseudoautosomal region of the human sex chromosomes. EMBO J 1987; 6: 963-69.
EPSTEIN-BARR VIRUS ASSOCIATED B-CELL LYMPHOMAS IN AIDS AND AFTER ORGAN TRANSPLANTATION
SIR,-Patients with AIDS are at increased risk of aggressive B-cell lymphoma. The involvement of Epstein-Barr virus (EBV) in these lesions is suggested by the detection of EBV genome and specific nuclear antigen (EBNA) in DNA extracts or tissue sections of the tumours .1-3 Kalter et al4 have reported that AIDS-related B-cell lymphomas are in two groups clinicopathologically, which
Fig 2-DNA from family probed with X-specific marker M27(3 (upper) or pseudoautosomal probe MR24/1 (lower). "Contaminated" samples were produced by mixing maternal DNA with DNA from son or daughter. Degree of maternal contamination, as % of total, is indicated Each track contained 5 Ilg DNA. Filters were exposed for 72 h (a) or 21 h (b). Left-hand track is HindIII digest of lambda phage DNA. Restriction enzymes were EcoRI for M27p and Hinfl for MR2411.
f = father; m = mother; d = daughter;
s=son.
suggest that the role of EBV may be different in the two types of lesion. Some of these tumours resemble the EBV-related B-cell disorders that develop in patients with primary immunodeficiency diseases and after organ transplantation;s some AIDS-related B-cell tumours, in contrast to transplantation-associated lymphoproliferation, resemble Burkitt lymphoma. 6 Normal B cells immortalised by EBV display latent viral gene expression, consisting of EBNA proteins 1-6 (M. J. Allday and others, unpublished) and latent membrane protein (LMP7). This is in contrast to the restricted expression of EBNA-1 in Burkitt lymphoma biopsy cells or freshly derived Burkitt lymphoma cell lines.7 Evidence that cytoadhesion molecules (LFA-1, ICAM-1, and LFA-3) are strongly expressed on immortalised B cell lines but weak or absent on Burkitt lymphoma tissue or early Burkitt lymphoma cell lines suggests that absence of these molecules is a
SIR,-Dr Krenning and colleagues (Feb 4, p 242) present a method for tumour localisation with a radioiodinated analogue of somatostatin (tyr-3-octrestide). Among the tumours that could be visualised were meningiomas, in which they had demonstrated somatostatin receptors.’ We report a 30-year-old man in whom a pituitary macroadenoma with intrasellar, parasellar, and suprasellar extension had been diagnosed two years before. The main symptoms were severe headaches which responded only to subcutaneous application of octreotide. The tumour had not been operated on because of an inborn deficiency of coagulation factor XI. Because the patient became tolerant the dosage had to be increased to 500 Ilg thrice daily. For endocrinological evaluation and to exclude possible psychological dependence, octreotide was replaced by subcutaneous injections of normal saline. Normal pituitary function was observed after withdrawal of octreotide and the tumour was shown to be hormonally inactive. However, after three days off octreotide the patient complained of headaches and demanded extra doses of octreotide. Neurological symptoms quickly developed and examination revealed bitemporal visual field defects for the first time; computerised tomographic scanning showed signs of obstructive hydrocephalus. Therefore we resumed the previous medication and 12 hours later headaches had resolved. During the following week visual fields were normal. X-ray after five days showed normal cerebral ventricles and a grossly unchanged tumour
(6 x 4 cm). Because of the need for continued octreotide administration with the development of tolerance, neurosurgical intervention was planned. After substitution of coagulation factors the tumour was subtotally resected. Histological examination of the resected tissue revealed haemangiopericytic meningioma. The patient has been well without octreotide for 4 months now. This outcome suggests favourable acute and chronic effects of octreotide on meningioma size. Scintigraphy with 123I-tyr-3octreotide may be of value in selecting patients with inoperable
somatostatin-receptor-positive meningiomas candidates for octreotide therapy.
as
potential
M. W. RÜNZI
C. JASPERS Departments of Medicine, Neurosurgery, and Neuropathology, University of Essen, 4300 Essen, West Germany
R. WINDECK G. BENKER H. M. MEHDORN V. REINHARDT D. REINWEIN
1. Reubi JC, Maurer R, Klijn JGM, et al. High incidence of somatostatin receptors in human meningiomas: biochemical characterisation. J Clin Endocrinol Metab 1986; 63: 433-38.
free GABA (32 and 25 nmol/1, control range 75-150) and homocamosine (2-5 and 0-9 umol/1, control range 4-10), which are features not previously reported in this condition. The clinical
picture was severe psychomotor retardation, generalised spasticity, and hyperexcitability but no convulsions. Vigabatrin 50 mg/kg per day was started in both children. Within a few days the spasticity and hyperexcitability significantly decreased while CSF GABA levels became normal. The only side-effect was drowsiness in one boy when on a daily dose of 75 mg/kg, but not when he was on 50 mg/kg. These findings suggest that low levels of GABA in the brain could contribute to the symptoms of metachromatic leucodystrophy and that vigabatrin may be a useful treatment for patients with this disease and perhaps other lysosomal disorders. Vigabatrin deserves careful evaluation in primary or secondary GABA metabolism disorders, even when not associated with convulsions. We thank Merrell Dow
(Belgium) for the supply of vigabatrin.
Department of Paediatrics, University Hospital Gasthuisberg, B-3000 Leuven, Belgium
JAAK JAEKEN PAUL CASAER PAUL DE COCK
Dr Willems
Institute, Diepenbeek, Belgium
BAUDOUIN FRANCOIS
1. Pattarelli PP, Nyhan WL, Gibson KM. Oxidation of (U - 14C) succinic semialdehyde in cultured human lymphoblasts: measurement of residual succinic semialdehyde dehydrogenase activity in 11 patients with 4-hydroxybutyric aciduria. Pediatr Res 1988; 24: 455-60. 2. Kolodny EH, Moser HW. Sulfatide lipidosis: metacliromatic leukodystrophy. In. Stanbury JB, Wijngaarden JB, Friedrickson DS, Goldstein JL, Brown MS, eds. The metabolic basis of inherited disease New York: McGraw-Hill, 1983. 881-905.
CHEST DRAIN THROMBECTOMY
SIR,-Blocked chest drains
are not only useless but also reinsertion of drains is difficult, painful, and hazardous, especially after thoracotomy. I have developed a simple technique to unblock chest drains with an arterial embolectomy catheter. This technique is safe, painless, repeatable, and usually successful. Under aseptic conditions a sterile, inflatable, balloon embolectomy catheter is passed proximally along the blocked drain. Intercostal drainage tubes are of a standard length (indicated on the packaging) and embolectomy catheters have a graduated scale; the catheter should be inserted to the limit of the drain only. A catheter with a balloon capacity of 0.75 ml is used. The balloon is inflated with sterile saline and the catheter withdrawn, retrieving the cause of obstruction, which is usually a blood or fibrin clot. Before the inflated balloon is removed from the drain a clamp may be applied to the drain more proximally, until the drain is connected to an underwater system. It is important not to overfill the balloon, which makes withdrawal difficult. This procedure may be repeated as
dangerous, and
accurate
necessary.
VIGABATRIN IN GABA METABOLISM DISORDERS
SiR,—Your March 11editorial focuses on the anticonvulsant properties of vigabatrin, an irreversible inhibitor of GABAaminotransferase, the first step in GABA catabolism. We report our experience with vigabatrin in three children with GABA metabolism disturbances not accompanied by epilepsy. A girl aged 2 years had ataxia and moderate psychomotor retardation due to succinic semialdehyde dehydrogenase deficiency, a defect in the second step of GABA catabolism. This condition is characterised by accumulation of y-hydroxybutyrate in body fluids.’ Vigabatrin 75 mg/kg per day was started in an attempt to reduce y-hydroxybutyrate concentration in the cerebrospinal fluid (CSF); the concentration decreased to 28% of pretreatment value (460 pmol/1) after a month of treatment. CSF free GABA had increased from 95 to 591 nmol/1 (control range for age, 75-150). Ataxia and the electroencephalographic epileptic sharp waves decreased and the improvement has persisted over the 16 months of treatment.
In two other children (boys aged 3 and 7 years) with metachromatic leucodystrophy2 we found decreased lumbar CSF
The technique has been used to salvage drains sited during thoracotomy and drains inserted percutaneously. I am unaware of any complications arising from this technique and it may be
applicable to drains in other sites. University Department of Surgery, General Infirmary at Leeds, Leeds LS1 3EX
R. H. DIAMENT
DETECTING MATERNAL CELL CONTAMINATION IN PRENATAL DIAGNOSIS
StR,—The Canadian multicentre studyl showed that chorionic villus sampling (CVS) is a reliable and accurate sampling procedure for prenatal diagnosis. CVS seems likely to become the prenatal diagnostic procedure of choice for most eligible pregnancies. However, in the Canadian study, maternal cell contamination was recognised in almost 4% of cases even though the trial participants
experienced operators. Furthermore, cytogenetic analysis detected maternal contamination in five cases of male fetuses for every female fetus, suggesting that maternal contamination in as were
1075 biochemical and molecular techniques there may be a serious risk of error. The polymerase chain reaction (PCR) technique is especially prone to error from maternal contamination. For these reasons we suggest that rapid and simple procedures based on hypervariable probes should be introduced into the CVS protocols for DNA diagnoses so that significant maternal contamination can be
recognised. Single locus hypervariable probes are available for the X chromosome and for the pseudoautosomal region common to both X and Y.2-5 Given that the frequencies of individual alleles for such genetic probes are generally less than 5% the probability of distinguishing between mother and fetus, thereby detecting possible maternal contamination, should exceed 99%. Fig 1 illustrates the patterns of restriction fragments that can be expected. We have tested this approach by mixing DNA from a mother and children, to achieve maternal contamination in the range 0-50%,
Fig 1—Possible patterns of restriction fragments indicating ease of detection of maternal contamination in male or female offspring and the identification of XO progeny.
(We thank Yumiko Ishakawa for this diagram.) 80% of the mother/daughter instances would go unrecognised. A 5-10% maternal contamination rate on routine many
as
CVS is probably a realistic expectation, even in good centres. Transabdominal chorionic biopsy is also inseparable from contamination by maternal tissue. When screening for cytogenetic abnormalities this degree of contamination is not too great a problem; however, with
and probing these mixtures with an X chromosome specific and pseudoautosomal probes (fig 2). Simulated maternal contamination can be detected at the 10% level with little difficulty. This application has the advantage that it employs similar procedures to the probe-based diagnostic tests for disease loci. The procedure we suggest has the additional advantage of detecting sex chromosome imbalances; it would also be able to distinguish XO from XY. The development of reagents to allow the extension of this approach to monitor the products from PCR amplification would be highly advantageous. Genetics
Laboratory, Department of Biochemistry, University of Oxford, Oxford OX1 3QU
IAN CRAIG MARK Ross JOHN H. EDWARDS
Murdoch Institute, Melbourne, Australia
NEIL FRASER
Clinical Genetics, University of British Columbia, Vancouver, Canada
JUDITH HALL
1 Canadian Collaborative CVS-amniocentesis Trial
2. 3.
4.
5.
Group. Multicentre randomised clinical trial of clorion villus sampling and amniocentesis. Lancet 1989; i: 1-6. Cooke HJ, Brown WRA, Rappold GA. Hypervariable telomeric sequences from the human sex chromosomes are pseudoautosomal. Nature 1985; 317: 687-91. Davies KE, Mandel J-L, Wiessenbach J, Fellous M. Report of the committee on the genetic constitution of the X- and Y-chromosomes. Cytogenet Cell Genet 1987; 46: 277-315. Fraser NF, Boyd Y, Brownlee G, Craig IW. Multi-allelic RFLP for M27&bgr;, an anonymous single copy genomic clone at Xp 11.3-Xcen. Nucleic Acid Res 1987; 15: 9616 Simmler MC, Johnsson C, Petit C, Rouyer F, Vergnaud G, Weissenbach J. Two highly polymorphic minisatellites from the pseudoautosomal region of the human sex chromosomes. EMBO J 1987; 6: 963-69.
EPSTEIN-BARR VIRUS ASSOCIATED B-CELL LYMPHOMAS IN AIDS AND AFTER ORGAN TRANSPLANTATION
SIR,-Patients with AIDS are at increased risk of aggressive B-cell lymphoma. The involvement of Epstein-Barr virus (EBV) in these lesions is suggested by the detection of EBV genome and specific nuclear antigen (EBNA) in DNA extracts or tissue sections of the tumours .1-3 Kalter et al4 have reported that AIDS-related B-cell lymphomas are in two groups clinicopathologically, which
Fig 2-DNA from family probed with X-specific marker M27(3 (upper) or pseudoautosomal probe MR24/1 (lower). "Contaminated" samples were produced by mixing maternal DNA with DNA from son or daughter. Degree of maternal contamination, as % of total, is indicated Each track contained 5 Ilg DNA. Filters were exposed for 72 h (a) or 21 h (b). Left-hand track is HindIII digest of lambda phage DNA. Restriction enzymes were EcoRI for M27p and Hinfl for MR2411.
f = father; m = mother; d = daughter;
s=son.
suggest that the role of EBV may be different in the two types of lesion. Some of these tumours resemble the EBV-related B-cell disorders that develop in patients with primary immunodeficiency diseases and after organ transplantation;s some AIDS-related B-cell tumours, in contrast to transplantation-associated lymphoproliferation, resemble Burkitt lymphoma. 6 Normal B cells immortalised by EBV display latent viral gene expression, consisting of EBNA proteins 1-6 (M. J. Allday and others, unpublished) and latent membrane protein (LMP7). This is in contrast to the restricted expression of EBNA-1 in Burkitt lymphoma biopsy cells or freshly derived Burkitt lymphoma cell lines.7 Evidence that cytoadhesion molecules (LFA-1, ICAM-1, and LFA-3) are strongly expressed on immortalised B cell lines but weak or absent on Burkitt lymphoma tissue or early Burkitt lymphoma cell lines suggests that absence of these molecules is a