Immunolocalization of βig-h3 Protein in 5q31-Linked Corneal Dystrophies and Normal Corneas

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Abstract
IN 4 clinically different, autosomal dominant corneal dystrophies, specific missense mutations have been reported in the βig-h3 gene (transforming growth factor β–induced gene) on chromosome 5q31.1-3 These include lattice corneal dystrophy type I (LCD-I), granular dystrophy (GCD), a mixed granular-lattice dystrophy called "Avellino dystrophy" (ACD), and Reis-Bücklers dystrophy. These dystrophies are defined by their clinical manifestations, combined with the microscopic and histochemical characteristics of their abnormal corneal deposits. Lattice corneal dystrophy type I has stromal deposits of an amyloid,4 GCD has accumulations of a crystalloid Masson trichrome red material ("hyaline"),5 and ACD dystrophy contains deposits of both.6 The name Reis-Bücklers dystrophy has been used for 2 superficial corneal dystrophies, both severely affecting the Bowman layer.7-12 One seems to be a superficial variant of GCD with rod-shaped Masson trichrome red deposits,13-15 subclassified by Küchle et al12 as corneal dystrophy of Bowman layer I (CDB-I).12 The more common entity (called Thiel-Behnke honeycomb dystrophy in Europe16 ) has deposits of "curly fibers" identifiable only by electron microscopy,17 and is subclassified as corneal dystrophy of Bowman layer II (CDB-II).12 The type of Reis-Bücklers dystrophy reported to have a βig-h3 mutation was not specified,1 but similarities of the rod-shaped type (CDB-I) to granular dystrophy and mapping of the curly fiber type (CDB-II) to a similar locus on chromosome 5q18 suggest that they both result from βig-h3 mutations.