Corneal dystrophy crystalline of Schnyder

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 98967

Definition

Schnyder corneal dystrophy (SCD) is a rare form of stromal corneal dystrophy (see this term) characterized by corneal clouding or crystals within the corneal stroma, and a progressive decrease in visual acuity.

Epidemiology

The prevalence of this form of corneal dystrophy is not known.

Clinical description

Lesions usually develop early in life and are mostly bilateral, but one eye may become affected prior to the other. Some patients complain of glare, which increases with age. Visual acuity gradually decreases. Associated systemic disorders have been commonly reported (hypercholesterolemia, arcus lipoides and genu valgum). Over time, small white opacities develop in the corneal stroma along with a diffuse haze. In about 50% of patients, crystals are not observed clinically.

Etiology

SCD is caused by various mutations in the UBIAD1 gene (1p36.22).

Diagnostic methods

Typically, a ring-shaped yellow-white opacity composed of innumerable fine needle-shaped crystals forms in Bowman layer and the adjacent anterior stroma of the central cornea. The crystals usually remain in the anterior third of the cornea. The corneal epithelium and endothelium as well as Descemet membrane are spared.

Differential diagnosis

SCD should be differentiated from other lipid keratopathies and particular from lecithin cholesterol acyltransferase disease (LCAT deficiency, see this term).

Genetic counseling

An autosomal dominant pattern of inheritance has been reported.

Management and treatment

The superficial pathologic corneal tissue needs to be excised.

Visit the Orphanet disease page for more resources.