Multiple myeloma in a pair of monozygotic twins: the first reported case.

A pair of monozygotic twins both developed multiple myeloma within a 2 year period. The first patient is alive with stable disease 4 years later, his twin brother died within a year of diagnosis. Monozygosity is well established and in both cases the paraprotein was IgG kappa. The relative influence of environmental and hereditary factors on the aetiology of myeloma is discussed. We believe this to be the first case of myeloma in twins to be reported.