ELECTRON-MICROSCOPIC OBSERVATION OF THE BASEMENT-MEMBRANE ZONE IN FOCAL DERMAL HYPOPLASIA

A 3-month-old boy had reticulated achromic and atrophic skin lesions o n the right buttock and thigh, as well as partial syndactyly of the th ird and fourth toes of the right foot, With hematoxylin and eosin stai n, an epidermal defect, abnormally located fat cell lobules, and absen ce of the upper and midportions of the dermis were observed, conformin g to a typical histopathologic picture of focal dermal hypoplasia, Ele ctron microscopic examination of the atrophic site showed loose collag en bundles, collagen fibers with loss of regular bands, abnormal fibro blasts, and disruption of the basement membrane zone, These defects in the basement membrane zone strongly suggest that abnormal formation o f type IV collagen is associated with focal dermal hypoplasia, and tha t this abnormal formation of collagen is correlated with the clinical sign of skin atrophy.