For many years, multiple sclerosis was thought to be a disease that is largely restricted to white early middle-aged females. It was thought to be rare in African-Americans. Several times a year, I hold "open houses" for families with multiple sclerosis at the Keck Center. I was surprised to find that as many as half of the people with multiple sclerosis who come to these meetings are black. The following is a study of mutliple sclerosis in French West Indies. There appears to be a doubling of the number of cases associated with return migration of people who had gone to France and the increase does not seem to be related to European ancestry in the people. The authors suggest that the increase is related to the environment rather than genetics, that there is some "precipitating environmental factors that operate in a critical way before the age of 15 years".


[*] Cabre P, Signate A, Olindo S, Merle H, Caparros-Lefebvre D, Bera O and Smadja D (2005). Role of return migration in the emergence of multiple sclerosis in the French West Indies. Brain The emergence of multiple sclerosis in island societies has been investigated only in a few Caucasian populations living in temperate regions. The effect of human migration on the risk of developing this disease is still an open question because of possible genetic selection. We conducted an epidemiological study of the multiple sclerosis population in the French West Indies (Martinique and Guadeloupe), a population which includes large numbers of West Indians who have returned after emigrating to metropolitan France. Standardized incidence ratios (SIRs) for multiple sclerosis among migrants were calculated and their genetic characteristics were compared to those of non-migrants. The crude prevalence of multiple sclerosis was 14.8/10(5) on December 31, 1999 (95% CI: 11.9-17.7); and its crude mean annual incidence for the period July 1, 1999 to June 30, 2002 was 1.4/10(5) (95% CI: 1.0-1.8), confirming its emergence in the French West Indies. Recurrent neuromyelitis optica, which is virtually the only form of multiple sclerosis in black African populations in tropical regions, represented not >17.8% of these cases. During the 1 440 000 person-years of follow-up, 33 incidence cases were identified in migrants. Since the number of expected cases was 19.3, the overall SIR was 1.71 (95% CI: 1.19-2.38; P < 0.01) among migrants. The increase in the SIR was more marked if the stay was made before the age of 15 years (4.05, 95% CI: 2.17-6.83; P < 0.0001). European ancestry in the two migrating and non-migrating populations was similar. Martinique, which has a higher rate of return migration, has a higher prevalence of multiple sclerosis (21.0/10(5) versus 8.5/10(5)) and a higher incidence (2.0/10(5) versus 0.7/10(5)) than Guadeloupe. The emergence of the disease in the French West Indies is of environmental rather than genetic origin. It may be explained either through the introduction by migrants of precipitating environmental factors that operate in a critical way before the age of 15 years, and/or by the recent disappearance from the French West Indies of protective environmental factors acting before this age. Department of Neurology, CHU Fort de France, Martinique, French West Indies, France.