What is your next step?
Answer: While the picture is suggestive of granular corneal dystrophy. a Congo red, PAS and trichrome stain should be ordered.
What is your diagnosis?
Granular corneal dystrophy. The deposits tend to be rectangular and strongly trichrome positive. Congo red and PAS are negative. Where they break through Bowman's membrane, the epithelium is injured.
This autosomal dominant condition is uncommon. Presentation in the fourth and fifth decade is usual. The gene is on chromosome 5. Several corneal dystrophies involve mutations in the TGFBI (BIGH3) gene on chromosome 5q31: three types of lattice corneal dystrophy (LCD), including type I and type IIIA, granular, Avellino (ACD), and Reis-Bucklers . Depending on the configuration of the resulting protein , differing location and staining properties result.
Biopsy is never indicated clinically but confirmation of the diagnosis is undertaken when grafting (the only treatment) is done.
Ref. Klintworth, GK: Advances in the molecular genetics of corneal dystrophies.Am. J. Ophthalmol 1999, 128:747-54.
