IgM deposition in skin biopsies from patients with primary biliary cirrhosis.

Immunofluorescence studies on skin biopsies from 14 patients with primary biliary cirrhosis (PBC) showed granular papillary deposition of IgM in all. In addition, 6 patients had C3 deposition. Control patients with various other liver diseases, idiopathic high plasma levels of igM and extrahepatic cholestasis were only sporadically positive for IgM and not at all for C3. IgM deposition in dermal papillae in PBC does not merely reflect high plasma IgM levels or cholestasis but probably represents an immunochemically abnormal IgM population.