Lipoid proteinosis: in vivo and in vitro evidence for a lysosomal storage disease.

Tissue and cultured fibroblasts derived from one patient with the classical findings of lipoid proteinosis have been used to examine pathologic mechanisms in the disease. Ultrastructural examination of the skin revealed not only extracellular deposits of finely granular, moderately electron dense material, but in addition the dermal fibroblasts characteristically demonstrated marked cytoplasmic vacuolization. Phase contrast microscopy of the cultured skin fibroblasts also showed strikingly abnormal cells with many inclusions, which by electron microscopy were delimited by a single membrane. Membranous lamellar material was also increased in these cells. Biochemical analysis of the fibroblasts revealed a 3- to 4-fold elevation in intracellular hexuronic acid. These morphologic and biochemical findings suggest certain similarities with known storage diseases and support the postulate that lipoid proteinosis may represent a lysosomal storage disease.