Skin biopsies from a patient with
hyalinosis cutis et mucosae (HCM) were studied by routine histology, electron microscopy, biochemical extractions, and immunofluorescence for
extracellular matrix proteins. The upper dermis consisted of large hyaline regions mainly composed of noncollagenous
proteins. A portion of this material was solubilized by reduction in 8 M
urea. Anti-sera against these
proteins revealed multiple
antigens most of which were also detectable in normal skin. The hyaline regions showed a reduced content of
collagens, particularly of thick fibrils and of
fibronectin. The basal lamina around capillaries and at the dermal-epidermal junction appeared as multiple, concentric layers of amorphous laminae intercalated with thin
collagen fibrils. They consisted of
collagens type III and IV and of
laminin as shown by immunofluorescence.
Antibodies could also be raised against
laminin of HCM skin which showed strong cross-reactions with authentic mouse
laminin. Cultured fibroblasts from the HCM lesion showed increased synthesis of noncollagenous
proteins at the expense of newly synthesized
collagens. Some but not all of these noncollagenous
proteins were also produced by fibroblasts from normal skin. The above data indicate that the hyaline material in HCM originates from the overproduction of noncollagenous
proteins, most of which are normal constituents of human skin.