Serum monoclonal immunoglobulins in childhood.

Of 18 children with monoclonal immunoglobulins in their sera, 13 had a primary or secondary immunodeficiency. The monoclonal immunoglobulin belonged to each of the three main Ig classes, and in 3 children multiple monoclonal components were detected. The level of the monoclonal component exceeded 0·5 g/100 ml in 7 cases. The monoclonal immunoglobulin disappeared spontaneously in 9 children. The significance of this homogeneous component and the importance of the underlying immunodeficiency are outlined.