Cancer Causesand Control, 3, 63 -67 Familial occurrence of hematolo.gic malignancies and other diseases in muluple myeloma: a case-control study Mikael Eriksson and Bengt Hfillberg (Received 23 September 1991; accepted in revised form 9 November 1991) In a population-based case-control study in Sweden on multiple myeloma, the occurrence of different diseases in relatives, particularly hematologic malignancies and different types of cancer, was investigated. Through a questionnaire mailed to all living subjects, i.e. cases and controls, and to the next-of-kin for deceased subjects, information was obtained on malignant and certain other diseases among relatives. All malignant diseases reported among first-degree relatives were verified, if possible, through parochial authorities and the Swedish Cancer Register. In total, data from 239 cases with myeloma and 220 controls were analyzed. An increased risk was found for persons with first-degree relatives with hematologic malignancies (relative risk [RR] = 2.36, 90 percent confidence interval [CI]=0.90-6.15), and also with multiple myeloma specifically (RR=5.64, CI = 1.16-27.51). An increased risk also was seen if the close relatives had experienced another tumor disease (RR= 1.21, CI = 0.86-1.71). Particularly, occurrence of prostatic cancer (RR = 3.11, CI = 1.25-7.71) or brain tumor (RR = 6.61, CI = 1.42-30.67) in relatives increased the risk for multiple myeloma. Key words: Case-control study, familial occurrence, multiple myeloma, Sweden. Introduction Although familial multiple myeloma (MM) was men- tioned briefly by the 1920s, m,2the first detailed case history, dealing with two sisters with MM, was pub- lished in 19542 Subsequent reports have been reviewed by Shoenfeld et al, 4 who found 36 families with at least two members affected by MM in the literature; further- more, they added a case history of their own. Twenty- seven of these 37 families involved siblings. Since this report, 11 additional case reports of fam- ilial MM have been published2 -H These reports, included a review of families with three affected sib- lings 8and two descriptions of monozygotic twins with MM. 7,9Moreover, two earlier publications of cases of MM and another type of lymphoproliferative disease in the same family12,~3 have been followed by a report including three similar relations. H In a hospital-based case-control study in the United States, 14 a family history of cancer of any type, as well as of hematologic malignancy, resulted in statistically sig- nificant increased relative risks (RR) for MM of 1.4 and 2.4, respectively. Furthermore, two US studies found increased risks for MM when first-degree relatives had degenerative or demyelinating central nervous system disorders, e.g. Parkinson's disease and multiple scler- osis, ~5 or rheumatoid arthritis, ~6 respectively. This report presents data on family history of dif- Dr Eriksson is with the Department of Oncology, University Hospital, S-901-85 Umed, Sweden. Dr Hdllberg is with the Department of Statistics, Umed University, Umed, Sweden. Address correspondence to Dr Eriksson. This research was supported by grants from the Swedish Cancer Fund. (Project 2683-B90-O2X.) © 1992 Rapid Communications of Oxford Ltd Cancer Causes and Control. Vol 3. 1992 63