The clinical appearance of the cornea in this disorder is non-specific with features found in as many as 75% of older individuals who do not have a corneal dystrophy. Some of the clinical findings are also found in other dystrophies such as Meesmann (122100), Reis-B?ocklers (608470), Lisch dystrophy (300778), lattice type I (122200), and Thiel-Behnke (602082). The common feature in all these is the formation of microcysts in the epithelium with alterations in the basement membrane. The pattern is sometimes described as a map-dot-fingerprint dystrophy. Corneal erosions occur in all to some degree and vision is minimally impacted. Many patients are asymptomatic unless corneal erosions occur.
Hereditary Cogan microcystic corneal dystrophy is sometimes diagnosed in the first decade of life but more characteristically found in people over the age of 30. The corneal changes wax and wane and are highly variable between patients. The dots consist of pseudocysts filled with intracellular debris while the geographic patterns are generated by multilayered basement membrane extensions into the epithelium. The rupture of these cysts results in corneal erosions. The underlying defect likely consists of defects in hemidesmosomal junctions.