Waldenström1 described three patients with excess homogeneous serum immunoglobulins but no evidence of malignancy and subsequently named the syndrome "benign monoclonal gammopathy."2 Larsson3 identified the first familial occurrence of benign monoclonal gammopathy and multiple myeloma in siblings. Subsequently, a number of reports of familial paraproteinemia have appeared.4-13 The incidence of familial paraproteinemia is higher than can be accounted for by chance alone.4,7,8 The cause of this familial association remains obscure. The present report of a mother with multiple myeloma and a son with benign monoclonal gammopathy illustrates an experimental approach toward evaluation of a possible genetic defect by examining the immunoglobulin products of these aberrant plasma cell clones from two related individuals.
The basic immunoglobulin molecule consists of two heavy and two light chains. There are five immunoglobulin classes based on the five types of heavy chains. Light chains also can be divided into two types