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.
