Hydrolysis of glucosylceramide by beta-glucocerebrosidase results in ceramide, a critical component of the intercellular lamellae that mediate the epidermal permeability barrier. A subset of type 2 Gaucher patients displays ichthyosiform skin abnormalities, as do transgenic Gaucher mice homozygous for a null allele. To investigate the relationship between glucocerebrosidase deficiency and epidermal permeability barrier function, we compared the stratum corneum (SC) ultrastructure, lipid content, and barrier function of Gaucher mice to carrier and normal mice, and to hairless mice treated topically with bromoconduritol B epoxide (BrCBE), an irreversible inhibitor of glucocerebrosidase. Both Gaucher mice and BrCBE-treated mice revealed abnormal, incompletely processed, lamellar body-derived sheets throughout the SC interstices, while transgenic carrier mice displayed normal bilayers. The SC of a severely affected type 2 Gaucher's disease infant revealed similarly abnormal ultrastructure. Furthermore, the Gaucher mice demonstrated markedly elevated transepidermal water loss (4.2 +/- 0.6 vs < 0.10 g/m2 per h). The electron-dense tracer, colloidal lanthanum, percolated between the incompletely processed lamellar body-derived sheets in the SC interstices of Gaucher mice only, demonstrating altered permeability barrier function. Gaucher and BrCBE-treated mice showed < 1% and < 5% of normal epidermal glucocerebrosidase activity, respectively, and the epidermis/SC of Gaucher mice demonstrated elevated glucosylceramide (5- to 10-fold), with diminished ceramide content. Thus, the skin changes observed in Gaucher mice and infants may result from the formation of incompetent intercellular lamellar bilayers due to a decreased hydrolysis of glucosylceramide to ceramide. Glucocerebrosidase therefore appears necessary for the generation of membranes of sufficient functional competence for epidermal barrier function.