Inherited snowflake cataracts.
The authors report two unusual pedigrees of flake-like cataracts inherited as an isolated mendelian trait, presumably autosomal dominant. The most striking biomicroscopic feature is an accumulation of large white irregular flakes ('type B opacities') scattered throughout the equatorial cortex, with apparently less involvement of the nucleus. Some of these opacities are globular, but most are flattened and have feathery edges. These type B opacities are clinically and microscopically identical in the two families. Type B lesions are characterized histologically by irregular pale-staining areas. Ultrastructurally, these areas show large collections of microglobular degeneration immediately adjacent to normal-appearing lens fibers. Electron probe studies demonstrate normal calcium levels. 'Type A' opacities are biomicroscopically smaller, punctate, and clinically non-specific. Ultrastructurally, type A opacities include clusters of medium sized lenticular globules, each of which is larger than the individual microglobular abnormalities of type B lesions, although the aggregated type B lesion is considerably larger than an individual type A lesion. The microscopic appearance of this inherited cataract appears to be unique.
D000328:Adult; D000368:Aged; D002386:Cataract / Q000235:genetics* / Q000473:pathology; D002648:Child; D003315:Cornea / Q000473:pathology; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D007908:Lens, Crystalline / Q000473:pathology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D010375:Pedigree