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The disturbances in odontogenesis in epidermolysis bullosa hereditaria letalis
The disturbances in odontogenesis in epidermolysis bullosa hereditaria letalis David G. Gardner, D.D.S., M.S.D.,* and Carolyn D. Hudson, B.D.S., M.S.D.,** London, Ontario, Canada, and London, England THE
UNIVERSITY
OF WESTERN
ONTARIO
AND
GUY’S
HOSPITAL
MEDICAL
SCHOOL
The disturbances in odontogenesis in a case of epidermolysis bullosa hereditaria letalis are described, with particular emphasis on the morphologic alterations in the ameloblasts and on the nature of vesicles in the enamel organ. These latter structures are compared to those found in the skin.
T
he term epidermolysis bullosa is applied to a group of inherited vesicular disorders of skin and mucous membranes. There is not complete agreement concerning the classification of epidermolysis bullosa, but one that is relatively well accepted includes a simplex form, a dyst,rophic form, and epidermolysis bullosa hereditaria letalis (EBHL). In turn, the dystrophic type is divided into a dominant hyperplastic form and a recessive polydysplastic form. Epidermolysis bullosa hereditaria letalis was first described in 1935 by Herlit and is a somewhat controversial disorder. It is considered by some to be simply a severe form of epidermolysis bullosa dystrophica polydysplasia. Others, notably Pearson and his colleagues,3 are convinced that it is a separate entity. The essential features of EBHL are the occurrence of vesicles at birth, death within the first 3 months of life, and the absence of milia or scarring. In addition, Pearson2 has shown that the separation of the epithelium from the connective tissue occurs above the basement membrane, the latter structure remaining with the underlying connective tissue. This finding has been confirmed recently by Pearson, Potter, and Strauss.3 Under the electron microscope, this splitting occurs between the plasma membrane of t,he basal cells and the basement membrane. In contrast, the separation in the recessive dystrophic type was found by Pearson* to be localized in the upper dermis, just below the basement membrane. This clear morphologic distinction between the two types of epidermolysis bullosa has been complicated by studies of other workers*, 5 who have found the type of splitting Presented in part at the twenty-ninth annual meeting Pathology, Kansas City, MO., April 21 to 25, 1975. *Professor and Chairman? Division of Oral Pathology, University of Western Ontarro. **Department of Oral Medicine and Pathology, Guy’s
of the
American
Faculties
of Dentistry
Hospital
Medical
Academy
of
Oral
and Medicine, School.
483
Pig. 1. Buccolingual section of the developing right mandibular first deciduous molar. TRIP area at the tip of the buccal cusp and the vesicle (8) are illustrated at higher magnifications in Figs. 2 and 5, respectively. ST Artefactual spaces; N, neonatal line. (Ikcalcifird sprcimm. Hematoxylin and eosin stain. Onginal magnification, x17.) Pig. 2. Higher magnification of the tip of the buccal cusp of the tooth illustrated in Fig. 1. There is present a thin layer of enamel which exhibits some lamination (arrow) and an irregular surface. The squamous epithelium at the tip of the cusp represents the reduced enamel epithelium. It is disorganized, and the cells are associated with numerous irregularly shaped globules exhibiting concentric lamination. Most are essentially basophilic, but some are eosinophilic, and one (A) has a basophilic periphery with an eosinophilic center. The appearance of this tissue is reminiscent of the calcifying epithelial odontogenic tumor. (Hematoxylin and eosin stain. Original magnificxtion, x130.)
Volume Number
40 4
Epidermolysis
bullosa hereditaria
letalis
485
3. Higher magnification of the concentric laminations and the squamous reduced epithelium from the tip of the cusp illustrated in Fig. 2. (Hematoxylin and eosin stain. magnification, x400.) Fig. 4. The globules are intimately related to the thin layer of enamel matrix which exhibits a Iamellar, nonprismatic structure. Both the globules and the enamel matrix are PAS positive. (Periodic acid-Schiff stain. Original magnification, x400.) Fig.
enamel Original
held by Pearson’ to be pathognomonic of EBHL in cases of the recessive dystrophic type. More work is required in this area. The purpose of this article is to describe the disturbances in odontogenesis in a case of EBHL, paying particular attention to the changes in the ameloblasts and to the nature of vesicles found in the enamel organ. These changes will be compared to those found in the skin.
Oral October,
Fig. deciduous membrane
5. The vesicle at the tip of the lingual cusp molar. The split is between the ameloblasts remaining with the odontoblasts. (Periodic
MATERIALS
AND
Surg. 1975
of the developing right mandibular first and the odontoblasts, with the basement acid-Schiff stain. Magnification, x400.)
METHODS
The specimen consisted of part of a mandible taken at autopsy from a Caucasian girl who had died of EBIIL at 6 weeks of age. There was no history of epidcrmolysis bullosa in the family, and this was the first child of parents who denied consanquinity. The specimen was radiographed and then decalcified in 10 per cent formic acid. With the radiographs serving as a guide, the specimen was then cut into appropriate blocks, double embedded, and stained with hematoxylin and eosin or periodic acid-Schiff. Sections of skin were stained by similar methods. RESULTS
The specimen contained three unerupted teeth-the first and second decidmolars and the first permanent molar. These teeth were at different stages of development.
uous
First
deciduous
molar
(Fig.
1)
A thin layer of enamel matrix, lacking any prismatic structure, had formed at the tip of the buccal cusp studied (h‘i g. 2). It was covered by a disorganized mass of squamous epithelium representing the premature alteration of the ameloblasts into reduced enamel epithelium. These cells were associated with numerous irregularly shaped globules exhibiting concentric laminations (Figs. 2 and 3). Both the enamel matrix and the globules were PAS positive. Fig. 4 illustrates the intimate relationship of the globules to the enamel matrix and the latter’s laminated structure. There was no evidence of prism formation. There was a vesicle at the tip of the lingual cusp where no hard tissues had yet formed. The split was bctwcen the amcloblasts and the odontoblasts. The PAS stain showed that the basement membrane had remained adherent to the odontoblastic layer (Fig. 5).
Volume Number
40 4
Epidermolysis
bullosa
hereditaria
letalis
Fig. 6. Buecolingual section of the developing right mandibular second deciduous Dentinogenesis has just commenced at the tip of the buccal cusp. This area is shown at magnification in Fig. 7. (Decalcified specimen. Hematoxylin and eosin stain. Original cation, x17.) Pig. 7. The tip of the buccal cusp of the developing second deciduous molar. A small of dentin exhibiting an unusually irregular surface has formed. The ameloblasts in this vacuolated and do not exhibit the typical nuclear orientation normally found in these enamel matrix has been secreted. (Hematoxylin and eosin stain. Original magnification,
Second
deciduous
molar
(Fig.
407
molar. a higher magnifiamount area are cells. No x250.)
6)
A small amount of dentin exhibiting an unusually irregular surface formed on the buccal cusp (Fig. i’), but none was found on the lingual. enamel had yet formed. The ameloblasts were vacuolated and disorganized did not exhibit the normal orientation of the nuclei at their proximal ends. terminal bars or Tomes’ processes were evident. First
permanent
molar
(Fig.
had No and No
81
Some dentin and a small amount of enamel matrix the buccal cusp examined. No hard tissues had formed
had formed at the tip of yet on the corresponding
Fig. 8. Buccolingual section of the developing right mandibular first permanent molar. Some dentin and a small amount of enamel matrix have formed at the tip of the huccal cusp. No hard tissues have formed yet on the lingual cusp, hut a vesicle is present between the amelohlasts and the odontohlasts. The area between the two arrows is further illustrated in Fig. 9. (Hematoxylin and eosin stain. Original magnificat,ion, x17.)
lingual cusp, where a vesicle was present bctwecn the ameloblasts and the odontoblasts. The ameloblasts appeared to have developed normally at first and induced the differentiation of odontoblasts from the mesenchymal cells of the dental papilla (Fig. 9). Further coronally, the odontoblasts had laid down the first dentin, which was normal except that the surfatc next to the ameloblasts was irregular. These cells had become disorganized and vacuolated and as yet had secreted no enamel matrix. Still further coronally, a small amount of enamel matrix had been secreted. The ameloblasts had regressed into short cells which lacked distal terminal bars and the nuclear polarization normally found in these cells. A markedly thin layer of enamel matrix was apparent at the tip of the buccal CUSP (Fig. 10). The ameloblasts in this area had lost their specialized morphology and exhibited no evidence of Tomes’ processes or distal terminal bars. A vesicle similar to that described in the first deciduous molar was present at the tip of the lingual cusp studied. No hard tissue had yet formed. The split was between the ameloblasts and the odontoblasts ; a PAS stain showed that the basement membrane had remained attached to the odontoblasts. Skin
The epithelium was separated from the dermis along the entire length of the specimen. Sections stained with PAS showed that the basement membrane remained attached to the dermis (Fig. 1I ) DISCUSSION
There have been two previous reports,“, ’ involving three cases, of the microscopic appearance of the developing teeth in EBHL. The findings in the present study are in general agreement with this earlier work.
Volume Number
40 4
Epidermolysis
bullosa
hereditaria
letalis
489
Fig. 9. Photomicrographs illustrating the sequential changes in the ameloblasts in the developing mandibular first permanent molar. A, St the apical end of the section, the ameloblasts appear normal and have induced the differentiation of odontoblasts from the cells of the dental papilla. H, Further coronally, the odontoblasts have laid down the first dentin, which is normal except that the surface next to the ameloblasts is irregular. The ameloblasts have become disorganized and vacuolated. No enamel matrix has yet been formed. C, Still further toward the tip of the cusp, a small amount of enamel matrix has been secreted. The ameloblasts have regressed into short cells lacking the nuclear polarization normally found in these cells. There is no evidence of distal terminal bars or Tomes’ processes. (Hematoxylin and eosin stain. Original magnification, x400.)
Oral October,
Fig 10. Photomicrograph of the illustrating the marked thinness of the specialized morphology. There is no (Hematoxylin and eosin stain. Original Fig. 11. Section of skin. There is basement membrane has remained with nification, x720.)
Surg. 1975
buccal cusp of the mandibular first permanent molar, enamel matrix (arrow). The ameloblasts have lost their evidence of Tomes’ processes or distal terminal bars. magnification, x165.) clear separation of the epithelium from the dermis. The the dermis. (Periodic acid-Schiff stain. Original mag-
It is apparent that the ameloblasts develop normally until such time as the first dentin is formed. At this stage, when amelogenesis should commence, they deposit a small amount of enamel matrix and then undergo premature squamous metaplasia into reduced enamel epithelium. This timing has been identical in all the teeth studied in the four cases so far reported. During odontogenesis, different teeth are at various stages of derelol~ment. The fact that the disturbance occurs at a particular stage in the development of the individual tooth indicates that the disturbance is not related to any chronologic insult. The vacuolization of the basal end of the ameloblasts in EBHL has been re-
Volume 40 Number 4
Epidermolysis
bulbosa hereditaria letalis
491
ported by Arwill and his colleagues” and is evident in the illustrations of Brain and Wigglesworth. However, neither group attempted to relate this morphologic finding to the pathogenesis of the condition. The vesicles in the present case occurred at the tips of the cusps between the ameloblasts and the odontoblasts. The basement membrane remained with the odontoblasts. This type of splitting, with the basement membrane remaining with the mesodermal cells, was found in the skin of this patient and has been emphasized by Pearson and his groupz~ 3 as being typical of EBHL. It seemsreasonable to conclude that the fault in the ameloblasts in this disease also occurs just above the basement membrane. The globules found in the reduced enamel epithelium of EBHL appear to represent enamel matrix similar to that first laid down by the ameloblasts in this condition. This conclusion is based on the apparent continuity of the two materials in someareas and on their similar staining properties. Normal enamel matrix is approximately 30 per cent calcified when first deposited. At this stage of primary calcification it is resistant to destruction by the decalcification procedures used in routine histologic technique and is intensely PAS positive. MaturaGon, or secondary calcification, when the enamel becomes approximately 96 per cent calcified, takes place later. Fully calcified enamel is destroyed during routine decalcification procedures in the laboratory. The enamel matrix, including the globules in the reduced enamel epithelium, in EBHL is PAS positive and resistant to decalcification in the histology laboratory. It therefore probably represents normal enamel matrix at the primary calcification stage. It is, however, not deposited in the normal prismatic pattern of enamel matrix which results from ameloblasts forming distal terminal bars and, therefore, Tomes’ processes. The ameloblasts in EBHL lack this ability, and the result is that the first thin layer of enamel matrix is laminated and the remainder forms globules. It is not clear why the initial secretion of enamel matrix is laminated rather than globular. Presumably, at first the ameloblasts retain sufficient organizational ability to lay the matrix down in layers. It is interesting to compare the alterations in amelogenesis in EBHL with those in regional odontodysplasia (ROD) .R In the latter condition some normal, prismatic enamel is formed. This enamel then becomes covered with a relatively amorphous material which is partly mineralized, PAS positive, and in some casesexhibits globules similar to those associated with the reduced enamel epithelium in EBHL. These globules are not as well formed as in EBHL, and relatively few cells of the reduced enamel epithelium are present. In EBHL no normal prismatic enamel matrix is formed. Instead, the first secretion of enamel matrix is laid down in a thin laminated layer and the remainder is secreted in globules separated from each other by numerous cells of the reduced enamel epithelium. One possible explanation for the alterations in the enamel in R(OD is that the ameloblasts in this disorder, having secreted some enamel matrix with the normal prismatic architecture, lose their ability to do so becausethey can no longer form distal terminal bars and, therefore, Tomes’ processes. They then simply secrete enamel matrix in a relatively amorphous manner with some globule formation. This situation would be comparable to that in EBHL in which the ameloblasts
Oral October,
Surg. 1975
never hail the ability to form terminal I~ara anal hciic~ to form prismatic enamel. If this hypothesis is correct. thcl partially valcifiecl material which covers the 11ormalprismatic c~numclill ROD rel)rrtsents cnamcl matrix which lacks the architectural structure of iio~~~al cuamol. This appears to IJC a better explanation than that which considers the material to represent dystrophic calcification of the degenerating enamel organ. Dentin does not appear to be affected specifically in EBHL, except that its surface is irregular. The marked tlisturbance in postnatal deposition of dentin in the case reported by Braiu and JVigglesworth’ is nonspecific and was probablr caused by the severe systematic tiisturbancc which EBHL represents. A few other findings in the previous studies on the developing teeth in EBHL require comment. Rrwill and his collcagucs’~ illustrated extensive vacuolization surrounding the globules assuciatetl with the reduced enamel epithelium. These vacuoles, which probabl;v rcprcscnt artefacts, were not found in Brain and Wigglesworth’s’ case or in the present study. Brain and Wigglesworth’ also noted “vesicle-like structures” in several locations on the surfaec of the developing teeth. These also appear to be artefactual. On the other hand, Fig. 7 of their article illustrates a vesicle at the tip of the lingual cusp of the first permanent Jnolar. This photomicrograph was taken at low power and does not show detail. However, the vesicle appears to bc similar to those found in the present study at the tips of those cusps where dcntinogcncsis had not yet occurred. Finally, Arwill and associates” noted a marked tendency for the outer enamel epithelinm to proliferate into the stcllate reticulum in EBHL. However, the proliferation of outer enamel epithclium with its supporting connective tissue is a normal occurrence during oclontogenesis. hmcloblasts, before the initial deposition of dentin, reccivc t.heir blood supply from the dental papilla. This source is compromisecl once dcntinogenesis begins. The proliferation of the outer enamel epithclium and supporting connecting tissno into the stellatc reticulum allows the blood vcsscls of thcl follicl(t to come closc~~to t,hc amcloblasts and therefore provide an alternate I~lood supply to thcsc ~11s. SUMMARY
This article describes the tlisturbanccs in odontogenesis in a case of EBHL, with particular emphasis on the morphologic alterations in the ameloblasts and to the nature of vesicles in the enamel organ. These latter structures are compared to those found in the skin. The authors are grntcful to Drs. N. 0. Doherty and S. F. Cahalane, The Children’s Hospit,al, Dublin, for supplying the material and details of the case and to Mrs. E. C. Jaffe, Guy’s Hospital, for assistance and adviw. This investigation was supported in part hy Grant MA3613 of the Medical Research Council of Canada. REFERENCES
I. Herlitz, G. : Kongenitsler, nieht syphilitischer Piner neuen Krxnkheitsform (Epidcrmolysis Stand. 17: 315371, 1935. 2. Pearson, R. W.: Studies on the Pathogencsis 39: 5X-575, 1962. 3. Pearson, R. W., Potter, H., and Strauss,
Pcmphigus bullosa
; Eine ijbersicht nebst Reschreibung hereditaria letalis), Aeta Paediatr.
of Epidermolysis F.:
Epiderrnolysis
Hullosa, Rullosa
J. Invest. Hereditaria
Dermatol. Letalis:
Volume Number
4.
5. 6. 7. 8.
40 4
Epidermolysis
bullosa hereditaria
letalis
493
Clinical and Histological Manifestations and Course of the Disease, Arch. Dermatol. 109: 349.355, 1974. Untersuchungen Lap&e, S., Castermans-Elias, S., and Firket, H.: Elektronenmikroskopische tiber die Ultrastriiktur der Epidermolysis bullosa letalis bei einem Saugling mit familiiirer Belastung, Hautarzt 15: 30.33, 1964. (Quoted in Gorlin, R. J. : Epidermolysis Bullosa, ORAL SURG. 32: 760-766, 1971.) Vogel, A., and Schnyder, U. W.‘: Feinstrukturelle Untersuchungen an rezessivdystrophischer Epidermolysis bullosa hereditaria, Dermatologica 135: 149-172, 1967. (Quoted in Gorlin, R. J.: Epidermolysis Bullosa, ORAL SURG. 32: 766766, 1971.) Armill, T.. Bewenholtz. A.. and O&on. 0.: Enidermolvsis Bullosa Hereditaria. III. A Histologic’ Study of Changes in Teeth in’ the Polydysplas&c Dystrophic and Lethal Forms, ORAL SURG. 19: 723-744, 1965. Brain, E. G., and Wigglesworth, J. S.: Developing Teeth in Epidermolysis Bullosa Hereditaria Letalis: A Histological Study, Br. Dent. J. 124: 255.260, 1968. Gardner, D. G., and Sapp, J. P.: Regional Odontodysplasia, ORAL SURG. 35: 351-365, 1973.
Reprint requests to : Dr. D. G. Gardner Department of Pathology University of Western Ontario London, Ontario N6A 5C1, Canada
UNIVERSITY
OF WESTERN
ONTARIO
AND
GUY’S
HOSPITAL
MEDICAL
SCHOOL
The disturbances in odontogenesis in a case of epidermolysis bullosa hereditaria letalis are described, with particular emphasis on the morphologic alterations in the ameloblasts and on the nature of vesicles in the enamel organ. These latter structures are compared to those found in the skin.
T
he term epidermolysis bullosa is applied to a group of inherited vesicular disorders of skin and mucous membranes. There is not complete agreement concerning the classification of epidermolysis bullosa, but one that is relatively well accepted includes a simplex form, a dyst,rophic form, and epidermolysis bullosa hereditaria letalis (EBHL). In turn, the dystrophic type is divided into a dominant hyperplastic form and a recessive polydysplastic form. Epidermolysis bullosa hereditaria letalis was first described in 1935 by Herlit and is a somewhat controversial disorder. It is considered by some to be simply a severe form of epidermolysis bullosa dystrophica polydysplasia. Others, notably Pearson and his colleagues,3 are convinced that it is a separate entity. The essential features of EBHL are the occurrence of vesicles at birth, death within the first 3 months of life, and the absence of milia or scarring. In addition, Pearson2 has shown that the separation of the epithelium from the connective tissue occurs above the basement membrane, the latter structure remaining with the underlying connective tissue. This finding has been confirmed recently by Pearson, Potter, and Strauss.3 Under the electron microscope, this splitting occurs between the plasma membrane of t,he basal cells and the basement membrane. In contrast, the separation in the recessive dystrophic type was found by Pearson* to be localized in the upper dermis, just below the basement membrane. This clear morphologic distinction between the two types of epidermolysis bullosa has been complicated by studies of other workers*, 5 who have found the type of splitting Presented in part at the twenty-ninth annual meeting Pathology, Kansas City, MO., April 21 to 25, 1975. *Professor and Chairman? Division of Oral Pathology, University of Western Ontarro. **Department of Oral Medicine and Pathology, Guy’s
of the
American
Faculties
of Dentistry
Hospital
Medical
Academy
of
Oral
and Medicine, School.
483
Pig. 1. Buccolingual section of the developing right mandibular first deciduous molar. TRIP area at the tip of the buccal cusp and the vesicle (8) are illustrated at higher magnifications in Figs. 2 and 5, respectively. ST Artefactual spaces; N, neonatal line. (Ikcalcifird sprcimm. Hematoxylin and eosin stain. Onginal magnification, x17.) Pig. 2. Higher magnification of the tip of the buccal cusp of the tooth illustrated in Fig. 1. There is present a thin layer of enamel which exhibits some lamination (arrow) and an irregular surface. The squamous epithelium at the tip of the cusp represents the reduced enamel epithelium. It is disorganized, and the cells are associated with numerous irregularly shaped globules exhibiting concentric lamination. Most are essentially basophilic, but some are eosinophilic, and one (A) has a basophilic periphery with an eosinophilic center. The appearance of this tissue is reminiscent of the calcifying epithelial odontogenic tumor. (Hematoxylin and eosin stain. Original magnificxtion, x130.)
Volume Number
40 4
Epidermolysis
bullosa hereditaria
letalis
485
3. Higher magnification of the concentric laminations and the squamous reduced epithelium from the tip of the cusp illustrated in Fig. 2. (Hematoxylin and eosin stain. magnification, x400.) Fig. 4. The globules are intimately related to the thin layer of enamel matrix which exhibits a Iamellar, nonprismatic structure. Both the globules and the enamel matrix are PAS positive. (Periodic acid-Schiff stain. Original magnification, x400.) Fig.
enamel Original
held by Pearson’ to be pathognomonic of EBHL in cases of the recessive dystrophic type. More work is required in this area. The purpose of this article is to describe the disturbances in odontogenesis in a case of EBHL, paying particular attention to the changes in the ameloblasts and to the nature of vesicles found in the enamel organ. These changes will be compared to those found in the skin.
Oral October,
Fig. deciduous membrane
5. The vesicle at the tip of the lingual cusp molar. The split is between the ameloblasts remaining with the odontoblasts. (Periodic
MATERIALS
AND
Surg. 1975
of the developing right mandibular first and the odontoblasts, with the basement acid-Schiff stain. Magnification, x400.)
METHODS
The specimen consisted of part of a mandible taken at autopsy from a Caucasian girl who had died of EBIIL at 6 weeks of age. There was no history of epidcrmolysis bullosa in the family, and this was the first child of parents who denied consanquinity. The specimen was radiographed and then decalcified in 10 per cent formic acid. With the radiographs serving as a guide, the specimen was then cut into appropriate blocks, double embedded, and stained with hematoxylin and eosin or periodic acid-Schiff. Sections of skin were stained by similar methods. RESULTS
The specimen contained three unerupted teeth-the first and second decidmolars and the first permanent molar. These teeth were at different stages of development.
uous
First
deciduous
molar
(Fig.
1)
A thin layer of enamel matrix, lacking any prismatic structure, had formed at the tip of the buccal cusp studied (h‘i g. 2). It was covered by a disorganized mass of squamous epithelium representing the premature alteration of the ameloblasts into reduced enamel epithelium. These cells were associated with numerous irregularly shaped globules exhibiting concentric laminations (Figs. 2 and 3). Both the enamel matrix and the globules were PAS positive. Fig. 4 illustrates the intimate relationship of the globules to the enamel matrix and the latter’s laminated structure. There was no evidence of prism formation. There was a vesicle at the tip of the lingual cusp where no hard tissues had yet formed. The split was bctwcen the amcloblasts and the odontoblasts. The PAS stain showed that the basement membrane had remained adherent to the odontoblastic layer (Fig. 5).
Volume Number
40 4
Epidermolysis
bullosa
hereditaria
letalis
Fig. 6. Buecolingual section of the developing right mandibular second deciduous Dentinogenesis has just commenced at the tip of the buccal cusp. This area is shown at magnification in Fig. 7. (Decalcified specimen. Hematoxylin and eosin stain. Original cation, x17.) Pig. 7. The tip of the buccal cusp of the developing second deciduous molar. A small of dentin exhibiting an unusually irregular surface has formed. The ameloblasts in this vacuolated and do not exhibit the typical nuclear orientation normally found in these enamel matrix has been secreted. (Hematoxylin and eosin stain. Original magnification,
Second
deciduous
molar
(Fig.
407
molar. a higher magnifiamount area are cells. No x250.)
6)
A small amount of dentin exhibiting an unusually irregular surface formed on the buccal cusp (Fig. i’), but none was found on the lingual. enamel had yet formed. The ameloblasts were vacuolated and disorganized did not exhibit the normal orientation of the nuclei at their proximal ends. terminal bars or Tomes’ processes were evident. First
permanent
molar
(Fig.
had No and No
81
Some dentin and a small amount of enamel matrix the buccal cusp examined. No hard tissues had formed
had formed at the tip of yet on the corresponding
Fig. 8. Buccolingual section of the developing right mandibular first permanent molar. Some dentin and a small amount of enamel matrix have formed at the tip of the huccal cusp. No hard tissues have formed yet on the lingual cusp, hut a vesicle is present between the amelohlasts and the odontohlasts. The area between the two arrows is further illustrated in Fig. 9. (Hematoxylin and eosin stain. Original magnificat,ion, x17.)
lingual cusp, where a vesicle was present bctwecn the ameloblasts and the odontoblasts. The ameloblasts appeared to have developed normally at first and induced the differentiation of odontoblasts from the mesenchymal cells of the dental papilla (Fig. 9). Further coronally, the odontoblasts had laid down the first dentin, which was normal except that the surfatc next to the ameloblasts was irregular. These cells had become disorganized and vacuolated and as yet had secreted no enamel matrix. Still further coronally, a small amount of enamel matrix had been secreted. The ameloblasts had regressed into short cells which lacked distal terminal bars and the nuclear polarization normally found in these cells. A markedly thin layer of enamel matrix was apparent at the tip of the buccal CUSP (Fig. 10). The ameloblasts in this area had lost their specialized morphology and exhibited no evidence of Tomes’ processes or distal terminal bars. A vesicle similar to that described in the first deciduous molar was present at the tip of the lingual cusp studied. No hard tissue had yet formed. The split was between the ameloblasts and the odontoblasts ; a PAS stain showed that the basement membrane had remained attached to the odontoblasts. Skin
The epithelium was separated from the dermis along the entire length of the specimen. Sections stained with PAS showed that the basement membrane remained attached to the dermis (Fig. 1I ) DISCUSSION
There have been two previous reports,“, ’ involving three cases, of the microscopic appearance of the developing teeth in EBHL. The findings in the present study are in general agreement with this earlier work.
Volume Number
40 4
Epidermolysis
bullosa
hereditaria
letalis
489
Fig. 9. Photomicrographs illustrating the sequential changes in the ameloblasts in the developing mandibular first permanent molar. A, St the apical end of the section, the ameloblasts appear normal and have induced the differentiation of odontoblasts from the cells of the dental papilla. H, Further coronally, the odontoblasts have laid down the first dentin, which is normal except that the surface next to the ameloblasts is irregular. The ameloblasts have become disorganized and vacuolated. No enamel matrix has yet been formed. C, Still further toward the tip of the cusp, a small amount of enamel matrix has been secreted. The ameloblasts have regressed into short cells lacking the nuclear polarization normally found in these cells. There is no evidence of distal terminal bars or Tomes’ processes. (Hematoxylin and eosin stain. Original magnification, x400.)
Oral October,
Fig 10. Photomicrograph of the illustrating the marked thinness of the specialized morphology. There is no (Hematoxylin and eosin stain. Original Fig. 11. Section of skin. There is basement membrane has remained with nification, x720.)
Surg. 1975
buccal cusp of the mandibular first permanent molar, enamel matrix (arrow). The ameloblasts have lost their evidence of Tomes’ processes or distal terminal bars. magnification, x165.) clear separation of the epithelium from the dermis. The the dermis. (Periodic acid-Schiff stain. Original mag-
It is apparent that the ameloblasts develop normally until such time as the first dentin is formed. At this stage, when amelogenesis should commence, they deposit a small amount of enamel matrix and then undergo premature squamous metaplasia into reduced enamel epithelium. This timing has been identical in all the teeth studied in the four cases so far reported. During odontogenesis, different teeth are at various stages of derelol~ment. The fact that the disturbance occurs at a particular stage in the development of the individual tooth indicates that the disturbance is not related to any chronologic insult. The vacuolization of the basal end of the ameloblasts in EBHL has been re-
Volume 40 Number 4
Epidermolysis
bulbosa hereditaria letalis
491
ported by Arwill and his colleagues” and is evident in the illustrations of Brain and Wigglesworth. However, neither group attempted to relate this morphologic finding to the pathogenesis of the condition. The vesicles in the present case occurred at the tips of the cusps between the ameloblasts and the odontoblasts. The basement membrane remained with the odontoblasts. This type of splitting, with the basement membrane remaining with the mesodermal cells, was found in the skin of this patient and has been emphasized by Pearson and his groupz~ 3 as being typical of EBHL. It seemsreasonable to conclude that the fault in the ameloblasts in this disease also occurs just above the basement membrane. The globules found in the reduced enamel epithelium of EBHL appear to represent enamel matrix similar to that first laid down by the ameloblasts in this condition. This conclusion is based on the apparent continuity of the two materials in someareas and on their similar staining properties. Normal enamel matrix is approximately 30 per cent calcified when first deposited. At this stage of primary calcification it is resistant to destruction by the decalcification procedures used in routine histologic technique and is intensely PAS positive. MaturaGon, or secondary calcification, when the enamel becomes approximately 96 per cent calcified, takes place later. Fully calcified enamel is destroyed during routine decalcification procedures in the laboratory. The enamel matrix, including the globules in the reduced enamel epithelium, in EBHL is PAS positive and resistant to decalcification in the histology laboratory. It therefore probably represents normal enamel matrix at the primary calcification stage. It is, however, not deposited in the normal prismatic pattern of enamel matrix which results from ameloblasts forming distal terminal bars and, therefore, Tomes’ processes. The ameloblasts in EBHL lack this ability, and the result is that the first thin layer of enamel matrix is laminated and the remainder forms globules. It is not clear why the initial secretion of enamel matrix is laminated rather than globular. Presumably, at first the ameloblasts retain sufficient organizational ability to lay the matrix down in layers. It is interesting to compare the alterations in amelogenesis in EBHL with those in regional odontodysplasia (ROD) .R In the latter condition some normal, prismatic enamel is formed. This enamel then becomes covered with a relatively amorphous material which is partly mineralized, PAS positive, and in some casesexhibits globules similar to those associated with the reduced enamel epithelium in EBHL. These globules are not as well formed as in EBHL, and relatively few cells of the reduced enamel epithelium are present. In EBHL no normal prismatic enamel matrix is formed. Instead, the first secretion of enamel matrix is laid down in a thin laminated layer and the remainder is secreted in globules separated from each other by numerous cells of the reduced enamel epithelium. One possible explanation for the alterations in the enamel in R(OD is that the ameloblasts in this disorder, having secreted some enamel matrix with the normal prismatic architecture, lose their ability to do so becausethey can no longer form distal terminal bars and, therefore, Tomes’ processes. They then simply secrete enamel matrix in a relatively amorphous manner with some globule formation. This situation would be comparable to that in EBHL in which the ameloblasts
Oral October,
Surg. 1975
never hail the ability to form terminal I~ara anal hciic~ to form prismatic enamel. If this hypothesis is correct. thcl partially valcifiecl material which covers the 11ormalprismatic c~numclill ROD rel)rrtsents cnamcl matrix which lacks the architectural structure of iio~~~al cuamol. This appears to IJC a better explanation than that which considers the material to represent dystrophic calcification of the degenerating enamel organ. Dentin does not appear to be affected specifically in EBHL, except that its surface is irregular. The marked tlisturbance in postnatal deposition of dentin in the case reported by Braiu and JVigglesworth’ is nonspecific and was probablr caused by the severe systematic tiisturbancc which EBHL represents. A few other findings in the previous studies on the developing teeth in EBHL require comment. Rrwill and his collcagucs’~ illustrated extensive vacuolization surrounding the globules assuciatetl with the reduced enamel epithelium. These vacuoles, which probabl;v rcprcscnt artefacts, were not found in Brain and Wigglesworth’s’ case or in the present study. Brain and Wigglesworth’ also noted “vesicle-like structures” in several locations on the surfaec of the developing teeth. These also appear to be artefactual. On the other hand, Fig. 7 of their article illustrates a vesicle at the tip of the lingual cusp of the first permanent Jnolar. This photomicrograph was taken at low power and does not show detail. However, the vesicle appears to bc similar to those found in the present study at the tips of those cusps where dcntinogcncsis had not yet occurred. Finally, Arwill and associates” noted a marked tendency for the outer enamel epithelinm to proliferate into the stcllate reticulum in EBHL. However, the proliferation of outer enamel epithclium with its supporting connective tissue is a normal occurrence during oclontogenesis. hmcloblasts, before the initial deposition of dentin, reccivc t.heir blood supply from the dental papilla. This source is compromisecl once dcntinogenesis begins. The proliferation of the outer enamel epithclium and supporting connecting tissno into the stellatc reticulum allows the blood vcsscls of thcl follicl(t to come closc~~to t,hc amcloblasts and therefore provide an alternate I~lood supply to thcsc ~11s. SUMMARY
This article describes the tlisturbanccs in odontogenesis in a case of EBHL, with particular emphasis on the morphologic alterations in the ameloblasts and to the nature of vesicles in the enamel organ. These latter structures are compared to those found in the skin. The authors are grntcful to Drs. N. 0. Doherty and S. F. Cahalane, The Children’s Hospit,al, Dublin, for supplying the material and details of the case and to Mrs. E. C. Jaffe, Guy’s Hospital, for assistance and adviw. This investigation was supported in part hy Grant MA3613 of the Medical Research Council of Canada. REFERENCES
I. Herlitz, G. : Kongenitsler, nieht syphilitischer Piner neuen Krxnkheitsform (Epidcrmolysis Stand. 17: 315371, 1935. 2. Pearson, R. W.: Studies on the Pathogencsis 39: 5X-575, 1962. 3. Pearson, R. W., Potter, H., and Strauss,
Pcmphigus bullosa
; Eine ijbersicht nebst Reschreibung hereditaria letalis), Aeta Paediatr.
of Epidermolysis F.:
Epiderrnolysis
Hullosa, Rullosa
J. Invest. Hereditaria
Dermatol. Letalis:
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4.
5. 6. 7. 8.
40 4
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Clinical and Histological Manifestations and Course of the Disease, Arch. Dermatol. 109: 349.355, 1974. Untersuchungen Lap&e, S., Castermans-Elias, S., and Firket, H.: Elektronenmikroskopische tiber die Ultrastriiktur der Epidermolysis bullosa letalis bei einem Saugling mit familiiirer Belastung, Hautarzt 15: 30.33, 1964. (Quoted in Gorlin, R. J. : Epidermolysis Bullosa, ORAL SURG. 32: 760-766, 1971.) Vogel, A., and Schnyder, U. W.‘: Feinstrukturelle Untersuchungen an rezessivdystrophischer Epidermolysis bullosa hereditaria, Dermatologica 135: 149-172, 1967. (Quoted in Gorlin, R. J.: Epidermolysis Bullosa, ORAL SURG. 32: 766766, 1971.) Armill, T.. Bewenholtz. A.. and O&on. 0.: Enidermolvsis Bullosa Hereditaria. III. A Histologic’ Study of Changes in Teeth in’ the Polydysplas&c Dystrophic and Lethal Forms, ORAL SURG. 19: 723-744, 1965. Brain, E. G., and Wigglesworth, J. S.: Developing Teeth in Epidermolysis Bullosa Hereditaria Letalis: A Histological Study, Br. Dent. J. 124: 255.260, 1968. Gardner, D. G., and Sapp, J. P.: Regional Odontodysplasia, ORAL SURG. 35: 351-365, 1973.
Reprint requests to : Dr. D. G. Gardner Department of Pathology University of Western Ontario London, Ontario N6A 5C1, Canada