Familial aggregation of multiple myeloma and central nervous system diseases.

Degenerative central nervous system diseases such as Alzheimer's disease and lymphoreticular malignancies such as multiple myeloma occur with increased frequency with advancing age. Relatives of early-onset Alzheimer's disease patients may have an increased risk of lymphoreticular malignancies. This led us to evaluate the family history of central nervous system diseases in a case-control study of multiple myeloma. Thirteen of 439 multiple myeloma cases had one or more first-degree relatives with degenerative or demyelinating central nervous system disease. In comparison, there were nine "positive" family histories in 1,317 matched hospital controls (relative risk = 4.4, 95% confidence interval = 1.9-10.3). Relative risks for the component categories of Parkinson's disease, multiple sclerosis, and miscellaneous degenerative central nervous system diseases were 3.0, 4.0 and 11.9, respectively. Our findings suggest that the degenerative and demyelinating central nervous system diseases and the lymphoreticular malignancies may comprise an etiologically related group of "protean diseases." These diseases may have a shared genetic susceptibility, possibly an immunologic abnormality. The varied disease manifestation in family members suggests a second necessary etiologic step of a variable and possibly environmental nature.