Fabry disease is the most common of the lysosomal storage disorders and results from deficient activity of the enzyme alpha-galactosidase A (a-Gal A), leading to progressive lysosomal deposition of globotriaosylceramide and its derivatives in cells throughout the body. The classic form, occurring in males with less than 1% a-Gal A enzyme activity, usually has its onset in childhood or adolescence with periodic crises of severe pain in the extremities (acroparesthesia), the appearance of vascular cutaneous lesions (angiokeratomas), sweating abnormalities (anhidrosis, hypohidrosis, and rarely hyperhidrosis), characteristic corneal and lenticular opacities, and proteinuria. Gradual deterioration of renal function to end-stage renal disease (ESRD) usually occurs in men in the third to fifth decade. In middle age, most males successfully treated for ESRD develop cardiac and/or cerebrovascular disease, a major cause of morbidity and mortality. Heterozygous females typically have milder symptoms at a later age of onset than males. Rarely, females may be relatively asymptomatic throughout a normal life span or may have symptoms as severe as those observed in males with the classic phenotype. In contrast, late-onset forms occur in males with greater than 1% a-Gal A activity. Clinical manifestations include cardiac disease, which usually presents in the sixth to eighth decade with left ventricular hypertrophy, cardiomyopathy, arrhythmia, and proteinuria; renal failure, associated with ESRD but without the skin lesions or pain; or cerebrovascular disease presenting as stroke or transient ischemic attack.

Schnyder corneal dystrophy (SCCD), also known as Schnyder crystalline corneal dystrophy, is an autosomal dominant eye disease characterized by abnormal deposition of cholesterol and phospholipids in the cornea. The consequent corneal opacification is progressive and bilateral, resulting in glare and loss of vision that is postulated to be caused by light scattering. Patients demonstrate a characteristic pattern of corneal opacification dependent on age, and only half have crystalline corneal cholesterol deposits. Patients with noncrystalline disease have a more subtle presentation with only corneal haze, which may be difficult to diagnose (summary by Nickerson et al., 2013).

Gelatinous drop-like corneal dystrophy is an autosomal recessive disorder characterized by severe corneal amyloidosis leading to blindness. Clinical manifestations, which appear in the first decade of life, include blurred vision, photophobia, and foreign-body sensation. By the third decade, raised, yellowish-gray, gelatinous masses severely impair visual acuity, and lamellar keratoplasty is required for most patients (summary by Tsujikawa et al., 1999).

Reis-Bucklers corneal dystrophy (CDRB) is an autosomal dominant disorder of the superficial corneal stroma that manifests as recurrent corneal erosions in early childhood. Affected individuals develop corneal opacities that result in significant visual impairment. Microscopically, CDRB may be differentiated from other forms of corneal dystrophy by confluent opacities in the Bowman layer and subepithelium, which are the product of extracellular bodies that stain red with Masson trichrome stain and appear as crystalloid rod-shaped bodies on transmission electron microscopy (summary by Tanhehco et al., 2006).

Dermochondrocorneal dystrophy, or Francois syndrome, is a rare disorder characterized by the development of skin nodules, acquired deformities of the extremities, and a corneal dystrophy. The corneal dystrophy is central and superficial with whitish subepithelial opacities (summary by Bierly et al., 1992).

Epithelial basement membrane corneal dystrophy (EBMD) is a common bilateral epithelial dystrophy characterized mainly by sheet-like areas of basement membrane originating from the basal epithelial cells of the corneal epithelium and extending superficially into the epithelium. Slit lamp examination may reveal dots, maps, grayish epithelial fingerprint lines, blebs, nets, or any combination of these patterns. Histologic analysis shows abnormal redundant basement membrane and intraepithelial lacunae filled with cellular debris. Most patients are asymptomatic before the age of 30 years; some may have recurrent erosions, the frequency of which declines with age, and a loss of vision due to surface irregularity (summary by Boutboul et al., 2006).

Mulibrey nanism (MUL) is a rare autosomal recessive growth disorder with prenatal onset, including occasional progressive cardiomyopathy, characteristic facial features, failure of sexual maturation, insulin resistance with type 2 diabetes, and an increased risk for Wilms tumor (summary by Hamalainen et al., 2006).

Oculodental syndrome, Rutherfurd type is a rare genetic disorder that is primarily characterized by the classical triad of gingival fibromatosis, non-eruption of tooth and corneal dystrophy (bilateral corneal vascularization and opacity). Abnormally shaped teeth have also been reported. The syndrome is transmitted as an autosomal dominant trait.

Thiel-Behnke corneal dystrophy (CDTB) is characterized by progressive honeycomb-like, subepithelial corneal opacities with recurrent erosions (Thiel and Behnke, 1967).

Central cloudy dystrophy of François is a very rare form of stromal corneal dystrophy (see this term) characterized by polygonal or rounded stromal opacities surrounded by clear tissue, and generally no effect on vision.

Macular corneal dystrophy (MCD) is an autosomal recessive disorder in which progressive punctate opacities in the cornea result in bilateral loss of vision, eventually necessitating corneal transplantation. MCD is classified into 2 subtypes, type I and type II, defined by the respective absence and presence of sulfated keratan sulfate in the patient serum, although both types have clinically indistinguishable phenotypes (summary by Akama et al., 2000).

Posterior polymorphous corneal dystrophy-3 (PPCD3) is a rare disorder involving metaplasia and overgrowth of corneal endothelial cells (Krafchak et al., 2005). In patients with PPCD, these cells manifest in an epithelial morphology and gene expression pattern, produce an aberrant basement membrane, and sometimes spread over the iris and nearby structures in a way that increases the risk for glaucoma. Symptoms range from very aggressive to asymptomatic and nonprogressive, even within the same family. The age of diagnosis is most often in the second or third decade of life. PPCD3 is often associated with corneal steepening, and some patients may be diagnosed with keratoconus before PPCD (Fernandez-Gutierrez et al., 2023). Retrocorneal membranes have been reported, sometimes extending onto the lens (Moroi et al., 2003). For a discussion of genetic heterogeneity of posterior polymorphous corneal dystrophy, see PPCD1 (122000).

Extremely rare syndrome with features of spastic ataxia in association with bilateral congenital cataract, corneal dystrophy, and nonaxial myopia. It has been described in an inbred Bedouin family. Immunological abnormalities were frequent. Transmission is autosomal recessive and the disease is monogenic.

Syndrome with the unusual combination of spinocerebellar degeneration and corneal dystrophy. Three sisters born to normal consanguineous parents have been reported, one of who had only minor spinocerebellar signs without ocular involvement. This autosomal recessive syndrome differs from the Mousa-Al-Din-Al-Nassar syndrome by the subnormal intellectual development and the epithelial (versus stromal) nature of the corneal dystrophy.

Fuchs endothelial corneal dystrophy (FECD) is a progressive, bilateral condition characterized by dysfunction of the corneal epithelium, leading to reduced vision. The prevalence of FECD has been estimated at about 5% among persons over the age of 40 years in the United States. The vision loss in patients with FECD results from a loss of corneal transparency associated with irregularity of inner corneal layers in early disease and edema of the cornea in advanced disease. Ultrastructural features of FECD include loss and attenuation of endothelial cells, with thickening and excrescences of the underlying basement membrane. These excrescences, called guttae, are the clinical hallmark of FECD and become more numerous with progression of the disease. As the endothelial layer develops confluent guttae in the central cornea, the cells are no longer able to keep the cornea dehydrated and clear (summary by Baratz et al., 2010). Genetic Heterogeneity of Fuchs Endothelial Corneal Dystrophy More common, late-onset forms of FECD have been shown to be caused by mutation in the SLC4A11 gene (610206) on chromosome 20p13 (FECD4; 613268), in the ZEB1 gene (189909) on chromosome 10p11.2 (FECD6; 613270), and in the AGBL1 gene (615496) on chromosome 15q25 (FECD8; 615523). Other loci for late-onset FECD have been identified on chromosomes 13pter-q12.13 (FECD2; 610158), 18q21.2-q21.32 (FECD3; 613267), 5q33.1-q35.2 (FECD5; 613269), and 9p (FECD7; 613271).

Posterior polymorphous corneal dystrophy-2 (PPCD2) is characterized by formation of blister-like lesions within the corneal endothelium or by regions of endothelial basement membrane thickening with associated corneal edema. The normal amitotic endothelial cells are replaced by epithelial-like cells that possess abundant intermediate filaments, desmosomes, and microvilli. The endothelium becomes multilayered and the abnormally proliferating cells may extend outwards from the cornea over the trabecular meshwork to cause glaucoma (summary by Biswas et al., 2001). For a general phenotypic description and a discussion of genetic heterogeneity of PPCD, see PPCD1 (122000).

Corneal endothelial dystrophy is characterized by thickening and opacification of the cornea, altered morphology of the endothelium, and secretion of an abnormal collagenous layer at the Descemet membrane (summary by Vithana et al., 2006).

Harboyan syndrome, or corneal dystrophy and perceptive deafness (CDPD), consists of congenital corneal endothelial dystrophy and progressive sensorineural deafness, and is transmitted as an autosomal recessive trait (summary by Desir et al., 2007).

Late-onset Fuchs endothelial corneal dystrophy (FECD) is a degenerative disorder affecting roughly 4% of the population older than 40 years. It is distinguished from other corneal disorders by the progressive formation of guttae, which are microscopic refractile excrescences of the Descemet membrane, a collagen-rich basal lamina secreted by the corneal endothelium. From onset, it usually takes 2 decades for FECD to impair endothelial cell function seriously, leading to stromal edema and impaired vision (Sundin et al., 2006). For a discussion of genetic heterogeneity of Fuchs endothelial corneal dystrophy, see FECD1 (136800).

Congenital stromal corneal dystrophy is characterized by the presence of bilateral corneal opacities that can be seen at or shortly after birth. The surface of the cornea is normal or slightly irregular; small opacities are seen throughout the stroma of the entire cornea and give the cornea a cloudy appearance. Strabismus is common. Nystagmus is uncommon. Amblyopia can develop in children.

A very rare form of stromal corneal dystrophy with characteristics of irregular amorphous sheet-like opacities in the posterior corneal stroma and in the Descemet membrane along with mildly impaired vision. Prevalence of this form of corneal dystrophy is not known. To date cases have been reported primarily in the USA. Patients usually develop corneal abnormalities in infancy or childhood. The condition is non-progressive or slowly progressive. Unlike other corneal dystrophies, non-corneal manifestations have been observed and include abnormalities of the iris including iridocorneal adhesions, corectopia, and pseudopolycoria. An autosomal dominant pattern of inheritance has been reported.

A rare subtype of posterior corneal dystrophy with characteristics of congenital ground glass corneal clouding or a diffuse corneal haze, and blurred vision in male patients. Prevalence of this rare corneal dystrophy is unknown. Males are affected more severely than females. The condition is progressive in males and non-progressive in females. Has been mapped to the long arm of the X-chromosome (Xq25) but the causative gene has not been identified. Transmission is X-linked recessive.

Fuchs endothelial corneal dystrophy (FECD) is the most common genetic disorder of the corneal endothelium. Late-onset FECD is marked by thickening of Descemets membrane and excrescences, called guttae, that typically appear in the fourth or fifth decade. Disease progression results in decreased visual acuity as a result of increasing corneal edema, and end-stage disease is marked by painful epithelial bullae (summary by Riazuddin et al., 2013). Patients with keratoconus have been observed (Lechner et al., 2013). For a discussion of genetic heterogeneity of Fuchs endothelial corneal dystrophy, see FECD1 (136800).

Fuchs endothelial corneal dystrophy (FECD) is the most common genetic disorder of the corneal endothelium. Late-onset FECD is marked by thickening of Descemets membrane and excrescences, called guttae, that typically appear in the fourth or fifth decade. Disease progression results in decreased visual acuity as a result of increasing corneal edema, and end-stage disease is marked by painful epithelial bullae (summary by Riazuddin et al., 2013). For a discussion of genetic heterogeneity of Fuchs endothelial corneal dystrophy, see FECD1 (136800).

Fuchs endothelial corneal dystrophy (FECD) is the most common genetic disorder of the corneal endothelium. Late-onset FECD is marked by thickening of Descemets membrane and excrescences, called guttae, that typically appear in the fourth or fifth decade. Disease progression results in decreased visual acuity as a result of increasing corneal edema, and end-stage disease is marked by painful epithelial bullae (summary by Riazuddin et al., 2013). For a discussion of genetic heterogeneity of FECD, see FECD1 (136800).

Keratosis follicularis spinulosa decalvans is an uncommon genodermatosis chiefly characterized by widespread keratosis pilaris, progressive cicatricial alopecia of the scalp, eyebrows, and eyelashes, and an excess of affected males. Photophobia, blepharitis/conjunctivitis, and corneal dystrophy are characteristic ancillary findings. It is most often inherited as an X-linked trait (summary by Castori et al., 2009). Autosomal dominant inheritance has also been reported (KFSD; 612843). The term 'cum ophiasi' means 'with ophiasis,' i.e., baldness in 1 or more winding streaks about the head, which comes from the Greek for snake. Decalvans refers to the loss of hair.

SHRF is an autosomal recessive disorder characterized by short stature, brachydactyly, dysmorphic facial features, hearing loss, and visual impairment. Onset of the hearing and visual abnormalities, including retinitis pigmentosa, varies from birth to the second decade. Patients have mild intellectual disability and mild cerebellar atrophy with myelination defects on brain imaging (summary by Di Donato et al., 2016).