Studies on a unique diagnostic serum globulin in papular mucinosis (lichen myxedematosus).

An abnormal γ-globulin present in the sera of five patients with papular mucinosis (PM) (lichen myxedematosus) appears to be characteristic of the disease. The PM protein is closely related to myeloma paraproteins in that it is homogeneous in electrophoretic mobility and homogeneous with respect to light chain antigenic groups. The consistently basic nature of the abnormal γ-globulin was shown by various electrophoretic techniques. In contrast to myeloma paraproteins, the light chains of all five of the PM proteins are L in type. The above characteristics of the PM γ-globulin and the benign clinical course differentiate papular mucinosis from multiple myeloma with cutaneous involvement.