CLINICAL, LIGHT AND ELECTRON-MICROSCOPIC FEATURES OF RECESSIVE CONGENITAL ICHTHYOSIS TYPE-I

Based on electron microscopic features, recessive congenital ichthyose s have recently been divided into four subgroups designated ichthyosis congenita (IC) types I, II, III and IV. Type II is characterized by c holesterol clefts in the horny cells, type III by perinuclear elongate d membranes in the granular and horny cells, and type IV by masses of lipid membranes in granular and horny cells. Clear electron microscopi c criteria for type I are lacking, although the presence of lipid drop lets in the horny cells has been suggested as a criterion. In the pres ent study we included ichthyosis patients with (i) recessive inheritan ce, (ii) erythrodermic fine scaling, (iii) lack of fine structural mar kers of IC types II-IV. Patients with ichthyotic syndromes were exclud ed. The case material consisted of 21 patients from 14 families. Eight were collodion babies at birth, but three were normal. Nine had ectro pion, the flexures were affected in 12, and the palms and soles were t hickened in all but one patient. On electron microscopy lipid vacuoles in the horny cells were common, but were absent in four patients. Cha nges in other lipid-related structures, including keratinosomes, were common. We conclude that currently type I can be diagnosed only by exc luding the other types of ichthyosis. Clinically, IC type I correspond s to classical non-bullous congenital ichthyosiform erythroderma, but there is marked heterogeneity among affected individuals.