Cutaneous periarteritis nodosa: immunofluorescence studies.

The study of ten cases of cutaneous periarteritis nodosa by direct immunofluorescence microscopy of excision biopsy specimens revealed positive findings in nine. Deposition of IgM was found in the vessel walls in six cases, and C3 was observed in four; however, only in two cases was C3 found with IgM in the vessel walls. Deposits of IgM in the superficial vessels were found in five cases, although only the deep muscular vessels showed evidence of the vasculitis in cutaneous periarteritis nodosa. Serum hepatitis B antigen was absent in the nine cases that were tested. Positive immunofluorescence findings in superficial as well as in deep vessels suggest that although periarteritis nodosa is characterized by an inflammatory panarteritis, occasional vasculitis of small vessels might be expected.