Macroglobulinaemia in an Icelandic family.

Macroglobulinaemia in an Icelandic family is presented. A woman had Waldenström's macroglobulinaemia, and two of her brothers had monoclonal macroglobulinaemia of the benign form. One was asymptomatic, but the other had polyneuropathy and IgM deposits in peripheral nerves. A third brother of these siblings died of a lymphoreticular disease, which presented with a widespread neuropathy. A second sister had polyclonal increase in serum IgA and two other brothers of this sibship had IgM slightly elevated. A study of all descendants (45 in all and 19 spouses) revealed seven individuals with elevated IgM levels. No other immunoglobulin abnormalities were detected.