Congenital hereditary stromal dystrophy

ETIOLOGY

Congenital hereditary stromal dystrophy (CHSD) is a very rare AD corneal dystrophy. Most of the genetic evidence points to the gene for decorin on chromosome 12.42 CHSD has not been linked to other associated ocular or systemic conditions.

CLINICAL PRESENTATION

Children with CHSD are born with bilateral corneal opacities. The opacity tends to be worse in the center of the cornea with gradual clearing in the peripheral cornea. Corneal thickness is normal in these patients, indicating irregular arrangement of collagen fibers as the cause of the opacity rather than swelling of the corneal stroma.43

MANAGEMENT/TREATMENT AND PROGNOSIS

Treatment for CHSD is similar to CHED. If the opacity is felt to be visually disabling corneal transplantation can be performed. Prognosis is largely based upon corneal graft survival and amblyopia treatment when needed.

90

Posterior polymorphous membrane dystrophy

ETIOLOGY

Posterior polymorphous membrane dystrophy (PPMD) is inherited in an autosomal dominant pattern. Multiple genetic loci on different chromosomes have been implicated in PPMD. Chromosomes 20p, 20q, 1p, and

10p have all been linked in different families with PPMD.44–46

CLINICAL PRESENTATION

Early opacification of the cornea has been reported with PPMD, but this is not the norm.47 Most patients with PPMD have a band-like opacity in Descemet’s membrane, often described as a ‘snail track’. The iris can be quite irregular in PPMD with adhesion to the peripheral cornea. With more severe PPMD,

glaucoma and corneal opacity are more common (90).48

The histopathologic findings in PPMD include areas of irregular corneal endothelial cells that look more like epithelial cells. These cells will grow across the cornea and onto the iris blocking fluid drainage from the eye (causing glaucoma). Irregularities in Descemet’s membrane have also been noted.49

MANAGEMENT/TREATMENT AND PROGNOSIS

Generally speaking PPMD has a mild course and many patients may not know they are affected. PPMD is not typically associated with other systemic findings. Ocular findings may include irregular pupils, glaucoma, and corneal opacity. Transplant is rarely indicated for PPMD; however, if the opacity is severe enough it may become necessary. One major difference between PPMD and the other corneal dystrophies is that the corneal swelling may spontaneously improve, negating the need for transplantation.