Granular Corneal Dystrophy Type 2 (GCD2)

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant dystrophy with very high penetrance, which is characterized by granular and linear deposits in the deep stroma in early stages and superficial diffuse haze in advanced stages (Han et al. 2010; Weiss et al. 2015). In 1938, Bücklers described a large family with the phenotype of GCD2, which has long been considered a mild variant of GCD1 (Weiss et al. 2015). Weidle reported and classified GCD patients according to subtle clinical differences in the 1980s. Folberg et al. demonstrated the histopathology of clinically atypical GCD with granular deposits in the anterior third of the stroma, and lattice-like amyloid deposits in the deeper stroma, which is now known as GCD2 (Folberg et al. 1988). In 1992, this dystrophy was separated from GCD and named Avellino corneal dystrophy, because the pedigree that was reported came from the Avellino district of Italy (Holland et al. 1992). This entity had been also described as combined granular-lattice corneal dystrophy before when the granular and linear lesions were observed in the same cornea together (Holland et al. 1992; Rosenwasser et al. 1993; Akiya et al. 1999). GCD2 is found worldwide now and is reported with greater frequently in East Asia (Korea and Japan) than in Italy (Lisch and Weiss 2019). The term GCD2 is consistent with the recommendations of the International Committee for Classification of Corneal Dystrophies (IC3D), published in 2008 (Weiss et al. 2008).