Numerous clinical reports and population or hospital-based surveys have reported familial aggregations of non-Hodgkin lymphoma (NHL), Hodgkin lymphoma, multiple myeloma, and chronic lymphocytic leukemia (CLL). The occurrence of more than one type of lymphoproliferative malignancy within the same family has also been described in case-control studies. The availability of register databases in Sweden and Denmark providing nationwide information on family cancer, hospitalization for medical conditions, cancer incidence, comprehensive population listings, and vital status and cause of death for deceased persons offer the unique opportunity to examine familial aggregation of lymphoproliferative malignancies and autoimmune diseases.
In very large case-control studies of first-degree relatives of cases with specific lymphoproliferative malignancies compared with first-degree relatives of controls, investigators in DCEG have found that first-degree relatives (N=70,006) of NHL cases (N=26,089) had modest to moderately increased risks of CLL, Hodgkin lymphoma, and NHL; relatives (N=14,336) of CLL cases (N=5,918) had significantly 7.5-fold increased risk of CLL, and smaller increases of NHL and Hodgkin lymphoma; relatives (N=22,984) of Hodgkin lymphoma cases (N=7,476) had significantly elevated risk of Hodgkin lymphoma, CLL, and NHL; but first-degree relatives (22,490) of multiple myeloma cases (N=8,406) did not have increased risks of lymphoproliferative malignancies other than multiple myeloma. Studies continue to assess: