Familial malignant blood disease in the country of Jämtland, Sweden.

In a material of 942 patients with malignant hematological disease, encompassing all diagnosed cases in the country of Jämtland in Sweden during a 22-yr period, 36 families with multiple cases of such disease were found. Approximately 5% of the patients have at least one close relative who also suffers from a malignant hematological disease. An especially strong familial occurrence was found in the group of chronic lymphoproliferative diseases and it is concluded that this tendency comprises all diseases in the group, i.e. chronic lymphocytic leukemia, multiple myeloma and malignant lymphoma. In some families several cases of acute leukemia were present, and suggestions concerning immunological disturbances are made. In the group of chronic myeloproliferative diseases familial factors do not seem to play an important part, with the possible exception of polycythemia vera. Both heredity and common environmental agents must be considered as possible etiologic factors.