Primary cutaneous amyloidosis: clinical, laboratorial and histopathological study of 25 cases. Identification of gammaglobulins and C3 in the lesions by immunofluorescence.

25 cases of primary cutaneous amyloidosis are studied. 16 patients had macular amyloidosis (MPA) and 9 lichen amyloidosus (LPA). gamma-Globulins were increased in 50% of the patients. IgG and IgA were increased in the serum of 5 and 3 patients with MPA and 4 and 2 patients with LPA, respectively. Volume of amyloid deposits was similar in both forms. By direct immunofluorescence we demonstrated IgG in the amyloid deposits of 21 of the 25 cases and C3 in 13; IgM was present in 9 cases of MPA and in 3 cases of LPA. MPA was more frequent than LPA; histologically, it was impossible to distinguish MPA from LPA; correlation between serum levels of gamma-globulins and their presence in amyloid deposits was weak; MPA and LPA seem to be distinct clinical manifestations of the same disease and itching does not cause transformation of MPA in LPA.