Ординатура / Офтальмология / Английские материалы / Ocular Pathology_6th edition_Yanoff, Sassani_2009

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appearance, even to containing goblet cells, but then, slowly, it is transformed into a more cornea-like appearance without goblet cells.

1.Stem cells can become exhausted in multiple conditions that lead to their massive direct injury or to repetitive insults.

2.The lacrimo-auriculo-dento-digital (LADD) syndrome is an autosomal-dominant disease with variable expression. Common ocular findings include hypoplasia or aplasia of tear glands, and lacrimal puncta or canaliculi, tear deficiency, recurrent or chronic conjunctivitis, keratoconjunctivitis sicca, and corneal ulceration secondary to sicca. Corneal stem cell deficiency and hypoanesthesia have also been described.

3.Similarly, ocular manifestations of keratitis–ichthyo- sis–deafness (KID) syndrome include lid abnormalities, corneal surface instability, limbal stem cell deficiency with secondary corneal complications, and dry eye.

4.Congenital abnormalities or deficiency of corneal limbal stem cells have been cited as responsible for keratopathy in aniridia, including corneal vascular pannus formation, conjunctival invasion of the

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Fig. 8.1 Cornea. A, The cornea contains five layers: epithelium, Bowman’s membrane, stroma, Descemet’s membrane, and endothelium. B, Increased magnification shows the nonkeratinized, approximately fivelayered epithelium, separated from Bowman’s membrane (relatively homogeneous) and anterior stroma (numerous large artifactitious clefts) by a thin basement membrane. C, Descemet’s (basement) membrane and endothelium (a single layer of cuboidal cells) cover the posterior stroma. (A–C, Periodic acid–Schiff stain.)

corneal surface, corneal epithelial erosions, and epithelial abnormalities. The disorder is secondary to heterozygosity for PAX6 deficiency (PAX6+/−).

Other possible causes for these changes include abnormal corneal healing responses secondary to anomalous extracellular matrix metabolism, abnormal corneal epithelial di erentiation leading to epithelial cell fragility, reduction in cell adhesion molecules in the heterozygous PAX6 state, and conjunctival and corneal changes leading to the presence of cells derived from conjunctiva on the corneal surface.

5.Idiopathic limbal stem cell deficiency has been reported.

D.Underlying the basal cell basement membrane is a thick, acellular, collagenous layer called Bowman’s membrane (by light microscopy) or Bowman’s layer (by transmission electron microscopy).

Abnormalities of corneal epithelium can be demonstrated clinically by the use of fluorescein or rose Bengal. Fluorescein staining is enhanced when disruption of cell–cell junctions occurs, whereas rose Bengal staining is seen with deficiency of protection by the preocular tear film.

E.The bulk of the cornea, the stroma, consists of collagen lamellae secreted by fibroblasts called keratocytes that lie between the lamellae.The stromal lamellae are arranged much as a collapsed honeycomb with oblique lamellae, the anteriormost lamellae (approximately one third) being the most oblique (i.e., the least parallel), and the posterior (approximately two-thirds) being the least oblique (i.e., the most parallel) to one another.

1.Thy-1 expression is present in cultured corneal fibroblasts and myofibroblasts, but not in fresh keratocytes. Thus, it may be used to di erentiate these cell types.

2.The anterior third of the stroma is analogous to a highly modified dermis of the skin, and the posterior two-thirds of the stroma may be usefully considered analogous to a highly modified subcutaneous tissue of the skin.

The Ocular Hypertension Treatment Study (OHTS) has drawn attention to the importance of variations in corneal thickness relative to the validity of applanation tonometry and the risk of glaucoma, with thin corneas resulting in inappropriately low intraocular pressure measurements and an associated increased risk of glaucoma. Similarly

marked increase in central corneal thickness (mean 632 μm) may be associated with aniridia, and may impact the accuracy of intraocular pressure measurements in this disorder. Similar increased corneal thickness has been reported in nevus of Ota. Decreased corneal thickness may result in an inappropriately low intraocular pressure in disorders such as osteogenesis imperfecta, and Down syndrome.

F.An unusually thick basement membrane, Descemet’s membrane, secreted by the endothelium, lies between the stroma and the endothelial cells.

Variably pigmented round and reticular posterior intracorneal precipitates have been described at the level of Descemet’s membrane in human immunodeficiency virus (HIV)-positive individuals.

G.The posterior surface of the cornea is covered by a single layer of cuboidal cells, the corneal endothelium (mesothelium); no hemidesmosomes are present along these inverted cells. Endothelial cells decrease progressively with age even in healthy emmetropic eyes.This decrease can be expedited by accompanying disorders such as pseudoexfoliation syndrome. The final common result of endothelial insu ciency is corneal edema.

1.Varying abnormalities in aquaporin distribution have been found in pseudophakic and aphakic bullous keratopathy, and in Fuchs’ corneal dystrophy, suggesting the possibility of variations in the mechanism for fluid accumulation in each disorder.

2.Corneal endothelial cell count is reduced and the coe cient of cellular variability is increased in type

II diabetes mellitus, but central corneal thickness is not increased.

3.Corneal endothelial cell numbers are decreased, and they express the characteristic mutant DRPLA protein in dentatorubropallidoluysian atrophy.

H.The cornea is one of the most unusual structures in the body in that it has no blood vessels and is transparent. Any pathologic lesions, therefore, are easily seen clinically as an opacification in the cornea.

I.The cornea is well innervated.

1.Approximately 20% of corneal nerves respond exclusively to noxious mechanical forces (mechanonociceptors), 70% are stimulated by extreme temperatures, exogenous irritant chemicals, and endogenous inflammatory mediators (polymodal nociceptors), and 10% are cold-sensitive and increase their discharge with moderate cooling of the cornea (cold receptors).

2.Increased tortuosity of corneal nerves as documented by CFM is associated with severity of somatic neuropathy in diabetes mellitus.

J.Although the corneal anatomy may be described as isolated layers for didactic purposes, pathologic conditions a ect multiple layers concurrently or sequentially. For example, multiple histologic structures, including corneal nerves, are adversely impacted by Sjögren’s syndrome.

CONGENITAL DEFECTS

Absence of Cornea

Absence of the cornea is a very rare condition usually associated with absence of other parts of the eye derived from primitive invaginating ectoderm (e.g., the lens).

Abnormalities of Size

I.Microcornea (<11 mm in greatest diameter; Fig. 8.2)

A.The eye is usually structurally normal.

Microcornea may be associated with other ocular anomalies such as are found in microphthalmos with cyst, trisomy 13, and the Nance–Horan syndrome (X-linked disorder typified by microcornea, dense cataracts, anteverted and simplex pinnae, brachymetacarpalia, and numerous dental anomalies; there is provisional linkage to two DNA markers—DXS143 at Xp22.3– p22.2 and DXS43 at Xp22.2).

B.The condition may be inherited as an autosomaldominant trait.

C.Histologically, the cornea is usually normal except for its small size.

A lack of myofilaments and desmin in the cytoplasm of the anterior layer of iris pigment epithelium suggests that congenital microcornea may result from a defect of intermediate filaments.

II. Megalocornea (>13 mm in greatest diameter; see Fig. 8.2)

A.Most megalocorneas present as an isolated finding, are bilateral and nonprogressive, and do not, in themselves, produce symptoms (except for refractive error).

Cataract and subluxated lens commonly develop in adulthood. Glaucoma may result secondary to the dislocated lens. Rarely, megalocornea is associated with renal cell carcinoma. In some families, renal cell carcinoma also develops in afflicted members.

Megalocornea, usually an isolated finding, may also be associated with ichthyosis, poikiloderma congenitale, Down’s syndrome, mental retardation, dwarfism, Marfan’s syndrome, craniostenosis, oxycephaly, progressive facial hemiatrophy, osteogenesis imperfecta, multiple skeletal abnormalities, nonketotic hyperglycemia, and tuberous sclerosis.

C.The condition usually has a recessive X-linked (in the region, Xq21–q26) inheritance pattern, but may be autosomal dominant or recessive.

D.Histologically, the cornea is usually normal except for its large size, especially in the limbal region.

Aberrations of Curvature

I. Astigmatism

II.Cornea plana

A.Frequently, cornea plana is associated with other ocular anomalies (e.g., posterior embryotoxon, colobomas of iris and choroid, and congenital cataract).

B.Both recessive and autosomal-dominant inheritance patterns have been reported, and both map to chromosome 12q21.

Mutations in keratocan is the probable mechanism of the

cornea plana phenotype. Recently, a new point mutation in exon 3 (937C > T) resulting in replacement of arginine by a stop codon at position 313 of keratocan protein has been associated with autosomal-recessive cornea plana, variable anterior-

chamber depths, and short axial lengths. Other mutations have been reported.

C.Histologically, the cornea is usually normal except for its flattened anterior curve.

III.Keratoconus and keratoglobus—see subsection Endothelial, section Dystrophies, later in this chapter.

Congenital Corneal Opacities

The two main theories of causation are arrested development during embryogenesis and intrauterine inflammation.

Similar changes can also result from trauma or inflammation. In a study of 72 eyes of 47 patients referred for congenital corneal opacities, Peters’ anomaly was the most common cause (40.3%), followed by sclerocornea (18.1%), dermoid (15.3%), congenital glaucoma (6.9%), microphthalmia (4.2%), birth trauma and metabolic disease (2.8%). 9.7% were idiopathic. Ten patients had systemic abnormalities associated with the ocular conditions.

Clinicopathologic Types—General

I.Facet

A.A facet (often the result of an embedded corneal foreign body) is a small, superficial spot seen by focal illumination as a distortion of the corneal light reflex or by slit lamp as a focal increased separation of the anteriormost two lines of corneal relucence.

B.Histologically, normal epithelium of increased thickness fills in the gap of previously abraded epithelium, focally absent Bowman’s membrane, and sometimes the

very anteriormost corneal stroma; no scar tissue is present.

II.Nebula (Fig. 8.3)

A.A nebula is a slight, di use, cloudlike opacity with indistinct borders.

B.Histologically, scar tissue is found predominantly in the superficial stroma.

III.Macula

A.A macula is a well-circumscribed, moderately dense opacity.

B.Histologically, the scar is dense and involves the corneal

stroma.

IV. Leukoma (Fig. 8.4; see also Fig. 8.10)

A.A leukoma is a white, opaque scar (e.g., see discussion of Peters’ anomaly, later).

B.Histologically, a large area of stromal scarring is present.

When iris is adherent to the posterior surface of the cornea beneath a region of corneal scarring, the resulting condition is called an adherent leukoma.

Clinicopathologic Types—Specific

I.Anterior embryotoxon

A.Anterior embryotoxon is synonymous with arcus juvenilis.

B.It may be present at birth or develop in early life, and clinically appears identical to an arcus senilis

(gerontoxon).

C.The condition may be associated with elevated serum lipids or cholesterol.

D.Histology—same as arcus senilis (see Fig. 8.20)

II.Corneal keloid

A.Corneal keloid presents as a hypertrophic scar involving the entire cornea.

If ectatic and lined by uveal tissue (iris), it is called a congenital corneal staphyloma.

B.Overabundant production of corneal scar tissue after trauma seems to be the cause of corneal keloid.

C.Although frequently noted at birth, probably secondary to intrauterine trauma, traumatic corneal keloids can occur at any age.They have been associated with Lowe’s

syndrome, Rubinstein–Taybi syndrome, fibrodysplasia ossificans progressiva, and other developmental ocular disorders.

D.Histologically, abundant scar tissue in disarray replaces most or all of the cornea.

Proliferating myofibroblasts (immunopositivity with alpha-smooth-muscle actin and the intermediate filament vimentin), activated fibroblasts, and haphazardly arranged fascicles of collagen may be seen.

III.De Barsy syndrome is characterized by anomalous facial appearance, generalized cutis laxa, mental retardation, hypotonia, hyperreflexia, growth retardation, and corneal opacification and degeneration of Bowman’s membrane.

A.Light microscopic examination of representative corneal tissue shows epithelial thickening, absence of Bowman’s membrane, and attenuation of stroma, particularly centrally. Hypercellularity and scarring of the anterior superficial stroma may also be seen.

B.Electron microscopy demonstrates replacement of the normal architecture of Bowman’s layer with a paucity of longitudinal and oblique collagen fibers. Although elastic fibrils are not usually present in the normal cornea, small bundles of elastic microfibrils are present in amorphous deposits that are immunopositive for elastin. Abnormal banding of Descemet’s membrane with normal-appearing endothelium may also be seen.

IV. Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy (APECED)

A.Seldom described, this is an autoimmune disorder that mainly a ects endocrine glands with manifestations such as adrenocortical failure, hypoparathyroidism, insulin-dependent diabetes mellitus, and pernicious anemia. Patients have chronic mucocutaneous candidiasis and ectodermal dystrophies.

B.Ocular manifestations include anterior keratopathy characterized by early epidermalization, destruction of

Bowman’s membrane and the anterior stroma, which

are replaced by vascularized scarring, proliferating

fibroblasts, and chronic inflammation. The deeper stroma, Descemet’s membrane, and endothelium are not a ected.

V.Central dysgenesis of cornea*

A.Peters’ anomaly (Fig. 8.5, see also section Fetal Alcohol

Syndrome in Chapter 2)

1.Peters’ anomaly consists of bilateral central corneal opacities associated with abnormalities of the deepest corneal stromal layers, including local absence of endothelium, and Descemet’s and Bowman’s membranes. Abnormalities of extracellular matrix may be present.

2.It is associated with anomalies of the anteriorsegment structures (corectopia, iris hypoplasia, anterior polar cataract, and iridocorneal adhesions).

Congenital corneal staphyloma has been seen.

3.The cause may be a defect of neural crest, ectoderm, and perhaps mesoderm, resulting in failure or delay in separation of the lens vesicle from surface epithelium. The causative event may occur in the migratory neural crest cells between the 4th and 7th weeks of gestation.

4.Associated systemic abnormalities include congenital heart disease, external ear abnormalities, cleft lip and palate, central nervous system abnormalities, hearing loss, and spinal defects.

a.Peters’ anomaly may be part of a new syndrome that includes microcephaly with cortical migra-

*Corneal endothelial cells, corneal stroma, portions of the trabecular meshwork including endothelial cells, anterior iris stroma, iris melanocytes, ciliary body, sclera, and intraocular vascular pericytes are derived not from meso-

derm, as thought previously, but from neural crest. Accordingly, the former term, mesodermal–ectodermal dysgenesis of cornea, now seems best replaced by central dysgenesis of cornea. Similarly, what was formerly termed mesodermal dysgenesis of cornea and iris now seems better termed peripheral dysgenesis of cornea and iris.

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tion defects, and multiple intestinal atresias. It is believed to be a multiple vascular disruption syndrome.

5.Peters’ anomaly is usually inherited as an autoso- mal-recessive trait, but autosomal dominance or no inheritance pattern may also occur.

Proliferating myofibroblasts (immunopositivity with alpha-smooth-muscle actin and the intermediate filament vimentin), activated fibroblasts, and haphazardly arranged fascicles of collagen may be seen.

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Fig. 8.5 Peters’ anomaly. The right (A) and left (B) eyes of a patient show bilateral central cornea leukomas and iris anomalies. C, In another patient, the right eye shows an enlarged cornea, secondary to glaucoma. The left eye shows a small cornea as part of the anomalous affliction. D, Histologic section shows considerable corneal thinning centrally. The space between the cornea and the lens material is artifactitious and secondary to shrinkage of the lens cortex during processing of the eye. E, Increased magnification shows lens material attached to the posterior cornea. Centrally, endothelium, Descemet’s membrane, and Bowman’s membrane are absent. Lens capsule (c) lines the posterior surface of the cornea (ce, corneal epithelium; cs, corneal stroma; lc, lens capsule).

(B and C, Periodic acid–Schiff stain; reported in Scheie HG, Yanoff M:

Arch Ophthalmol 87:525, 1972. American Medical Association. All rights reserved.)

Peters’ anomaly may be associated with deletion of short arm of chromosome 4 (Wolf–Hirschhorn syndrome), partial trisomy 5p, mosaic trisomy 9, deletion of long arm of chromosome 11, deletion of 18q, ring chromosome 21, interstitial deletion 2q14q21, and translocation (2q;15q). It has also been reported in association with ring 20 chromosomal abnormality, trisomy 13, the Walker–Warburg syndrome, and the fetal alcohol syndrome (see Fig. 2.14). Also, in a family that has Axenfeld syndrome and Peters’ anomaly, the condition was caused by a point mutation (Phe112Ser) in the FOXC1 gene

6.Internal ulcer of von Hippel is similar to Peters’ anomaly in that patients show the typical corneal abnormalities, but di ers in that no lens abnormalities are present.

Similar findings have been reported in cerebro-ocular myopathy syndrome.

7.Histologically, endothelium, and Descemet’s and Bowman’s membranes are absent from the cornea centrally, usually along with varying amounts of posterior stroma.

a.The corneal lamellae are more compact and more irregularly packed than normal corneal lamellae.

b.Immunohistochemistry shows an increase in

fibronectin and collagen type VI.

c.Lens abnormalities are present (usually an anterior polar cataract); associated abnormalities of the iris and other structures may also be present.

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B.Localized posterior keratoconus (Fig. 8.6)

1.Localized posterior keratoconus consists of a central or paracentral, craterlike corneal depression associated with stromal opacity. The depression involves the posterior corneal surface.

2.Unlike Peters’ anomaly, endothelium and Descemet’s membrane are present.

3.No other ocular anomalies are seen.

4.Neural crest–mesenchymal maldevelopment, infection, and trauma are proposed causes.

5.Histologically, the posterior curve of the cornea is abnormal, the overlying collagen of the corneal stroma is in disarray, and Bowman’s membrane may

be absent centrally.

VI. Peripheral dysgenesis of the cornea and iris*

Peripheral dysgenesis of the cornea and iris includes a wide spectrum of developmental abnormalities, ranging from posterior embryotoxon (Axenfeld’s anomaly) to extensive anomalous devel-

*See footnote on page 260.

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opment of the cornea, iris, and anterior-chamber angle associated with systemic abnormalities (Rieger’s syndrome).* An associated congenital glaucoma may occur, but the presence or absence of glaucoma does not necessarily depend on the degree of malformation. The abnormalities may be congenital, noninfectious, and noninherited (e.g., as part of trisomy 13 and partial trisomy 16q); congenital and inherited (e.g., Rieger’s syndrome); or congenital and infectious (e.g., rubella syndrome).

A.Posterior embryotoxon or embryotoxon corneae posterius (Axenfeld’s anomaly; Axenfeld–Rieger anomaly;

Fig. 8.7)

1.Recognized clinically as a bowor ring-shaped opacity in the peripheral cornea, posterior embryotoxon is an enlarged ring of Schwalbe located more centrally than normally.

2.It is often seen in an otherwise normal eye, or one that shows only a few mesodermal strands of iris tissue bridging the chamber angle to attach to the

“displaced” Schwalbe ring.

3.Posterior embryotoxon may be accompanied by glaucoma.

4.Although most cases are not inherited, dominant and recessive autosomal pedigrees have been reported; the former often has prominent iris involvement.

*The di erentiation between Axenfeld’s anomaly and Rieger’s syndrome is one of degree and therefore subject to a host of interpretations and classifications. The classification used here is chosen for its simplicity and because it is as close as possible to what Axenfeld and Rieger described originally. Axenfeld in 1920 described a boy with a white annular corneal line approximately 1 mm from the limbus, at the level of Descemet’s membrane. At this level, a semitransparent opacity was observed between the line and the limbus. From the anterior layer of the poorly developed iris stroma (partial iris coloboma),

a number of delicate fibrillae traversed the anterior chamber toward this line. He called the abnormality embryotoxon corneae posterius. Axenfeld’s

patient did not have glaucoma. Rieger in 1935 described a more marked iridocorneal defect in a mother and her two children, showing an autosomaldominant inheritance pattern. In 1941, Rieger showed an association with dental abnormalities, particularly oligodontia or anodontia.

Axenfeld–Rieger anomaly has been linked to chromosome 6p25 (FKHL7 gene). Posterior embryotoxon (along with microcornea, mosaic iris stromal hypoplasia, regional peripapillary retinal depigmentation, congenital macular dystrophy, and anomalous optic discs) may be associated with arteriohepatic dysplasia (Alagille’s syndrome), an autosomal-dominant intrahepatic cholestatic syndrome. Posterior embryotoxon, iris abnormalities, and diffuse fundus hypopigmentation, together with neonatal jaundice, are highly characteristic of Alagille’s syndrome, which also has a strong association with optic drusen. Another association may be with oculocutaneous albinism.

B.Axenfeld–Rieger syndrome (Rieger’s syndrome; Fig. 8.8)

1.The syndrome includes Axenfeld’s anomaly together with more marked anomalous development of the limbus, the anterior-chamber angle, and the iris

(ectopia of the pupil, dyscoria, slit pupil, severe hypoplasia of the anterior layer of the iris, iris strands bridging the anterior-chamber angle).

Axenfeld–Rieger’s syndrome can be found as part of the SHORT syndrome (short stature, hyperextensibility of joints or hernia, ocular depression, Axenfeld–Rieger’s syndrome, and teething delay). Axenfeld–Rieger’s syndrome is different from iridogoniodysgenesis, which does not have a linkage to the 4q25 region (see later).

2.Glaucoma may be present (approximately 60% of cases).

3.Facial, dental, and osseous abnormalities are present.

Associated neurocristopathy has been reported.

4.It is inherited as an autosomal-dominant trait, and probably represents abnormal embryonic development of the cranial neural ectoderm.

Genetic causes of Axenfeld–Rieger syndrome include mutations, deletions, or duplications of the forkhead-

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Fig. 8.8 Rieger’s syndrome. A, The patient has numerous iris abnormalities and bilateral glaucoma. Note the hypertelorism. B, The patient’s daughter has similar abnormalities. Note the iris processes attached to an anteriorly displaced Schwalbe line (anterior embryotoxon).

C, Histologic section of an eye from another patient shows an anteriorly displaced Schwalbe ring (s). A diffuse abnormality of the iris stroma is present (c, cornea; i, iris; ir, iris root; cp, ciliary process). (A and B, Courtesy of Dr. HG Scheie.)

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related transcription factor FOXC1, as mutations of the homeodomain (HD) protein PITX2 (PITX2 gene; chromosome 4q25). Axenfeld–Rieger syndrome caused by a deletion of the paired-box transcription factor PAX6 has been reported. Finally, a family has been described that has Axenfeld syndrome and Peters’ anomaly caused by a point mutation (Phe112Ser) in the FOXC1 gene

VII. Endothelial dystrophy, iris hypoplasia, congenital cataract, and stromal thinning (EDICT) syndrome

Autosomal-dominant syndrome that has been mapped to chromosome15q22.1-q25.3.

VIII. An additional familial anterior-segment dysgenesis syndrome includes iris and corneal abnormalities and cataracts.

Histopathologic and electron microscopic examination shows attenuated endothelium with prominent intracellular random aggregates of small-diameter filaments that stained positively for cytokeratin. Other features include abnormal, thickened Descemet’s membrane, layered electron-dense material within variably sized vacuoles within and between collagen lamellae and within keratocytes throughout the stroma and Bowman’s membrane.

IX. Sclerocornea

A.This condition, usually bilateral, may involve the whole cornea or only its periphery, with superficial or deep

vascularization. The cornea appears white and is di - cult to di erentiate from sclera.

B.Nystagmus, strabismus, aniridia, cornea plana, horizontally oval cornea, glaucoma, and microphthalmos may be present.

C.Congenital cerebral dysfunction, deafness, cryptorchidism, pulmonary disease, brachycephaly, and defects of the face, ears, and skin may also be seen.

D.The condition occurs in three ways: sporadic, isolated cases; familial cases in siblings but without transmission to other generations; and as a dominantly inherited disorder.

Sclerocornea has been described in Mietens’ syndrome.

E.Histologically, the most frequent findings are increased numbers of collagen fibrils of variable diameters, a decrease in the diameters of collagen fibrils from the anterior to the posterior layers, and a thin Descemet’s membrane.

Sclerocornea is mainly a clinical descriptive term, and a distinct clinicopathologic entity of sclerocornea probably does not exist.

X.Limbal (corneal; epibulbar) dermoids (Fig. 8.9)

A.Limbal dermoids are unusual congenital anomalies that contain mesoblastic tissues covered by epithelium.

X-linked recessive inheritance has been reported.

B.They usually occur at the temporal or superior temporal limbal area, but may involve the entire cornea.

1.Rarely, they may extend through the sclera into the uvea.

2.Dermoids are choristomas, congenital rests of benign tissue elements in an abnormal location.

a.Other choristomas in this region include dermolipomas, lacrimal gland choristomas, osseous choristomas, and complex choristomas.

3.Corneal keloid may mimic dermoid recurrence following surgical excision of the latter lesion.

C.Histologically, they contain choristomatous tissue

(tissue not normally found in the area) such as epidermal appendages, fat, smooth and striated muscle, cartilage, brain, teeth, and bone.

1.They are covered by corneal or conjunctival epithelium.

2.They may be cystic or solid.

D.Goldenhar’s syndrome (Goldenhar–Gorlin syndrome, oculoauriculovertebral dysplasia; see Fig. 8.9)

Goldenhar described the triad of epibulbar dermoids, auricular appendages, and pretragal fistulas in 1952. Gorlin, 11 years later, showed the added association with microtia and mandibular vertebral abnormalities (i.e., oculoauriculovertebral dysplasia).

1.Goldenhar–Gorlin syndrome is a bilateral condition characterized by epibulbar dermoids, accessory auricular appendages, aural fistulas, vertebral anomalies, and hypoplasia of the soft and bony tissues of the face.

Upper-eyelid colobomas commonly occur, but lowereyelid pseudocolobomas are more often associated with the Treacher Collins–Franceschetti syndrome. Epibulbar choristoma, similar to that seen in Goldenhar’s syndrome, has been seen in a patient with nevus sebaceus of Jadassohn.

2.Sometimes it is associated with phocomelia and renal malformations.