Geographic Distribution of Sporadic and Familial Multiple Sclerosis in Lebanon

Background/Objective(s) Familial aggregation of multiple sclerosis (MS) within Lebanon raises the question of potential areas of genetic clustering . The objective of this study was to compare demographic, clinical, and geographic characteristics of sporadic and familial MS patients. We conducted an exploratory study to identify the presence of any geographic genetic clustering of familial MS within Lebanon. Material(s) and Method(s) We administered a survey to 1056 sequentially recruited patients at the AUBMC Multiple Sclerosis Center over the span of 3 years. We collected demographic and clinical information from each patient. For patients residing within Lebanon, we also collected information about the governorate and district of birth and of residence until 15 years old. Demographic and clinical variables where compared between the familial and sporadic groups using independent t-test and chi-square tests. Geographic distributions were expressed as counts and as rates per 100,000 using the latest population estimates and were compared using the chi-square test. Result(s) Among the 1056 patients, 66.6% were female and the average age of onset was 28.7 ± 10.2 years. No significant difference was observed in terms of sex, age at onset, or diagnosis between sporadic and familial groups. Approximately 80% of the sample (n = 844) were born in Lebanon and 84% (n = 881) resided in Lebanon until the age of 15. Of the 844 patients born in Lebanon, 190 had a family history of MS (22.5%; 95% CI [0.2, 0.25]). Beirut exhibited the highest MS rates per 100,000 both by birth (93.9 overall; 73.2 sporadic; 20.8 familial) and residence until age 15 (100.4 overall; 77.3 sporadic; 23.1 familial). Secondary concentrations were observed in the Western Bekaa, Tripoli and Sidon districts. Statistical analyses revealed no significant differences between governorates of birth and residence until 15 years (χ²=0.86, p=0.99) and no significant differences in distribution between sporadic and familial cases by either birth governorate (χ²=5.47, p=0.70) or residence until 15 years (χ²=5.19, p=0.73). Conclusion(s) From our sample, we estimate proportion of familial MS in Lebanon to be 22.5% (95% CI [0.2, 0.25]) with familial MS cases being proportionally distributed throughout the country. Both sporadic and familial cases cluster most prominently in Beirut, the Western Bekaa, Tripoli and Sidon districts. These findings argue against regional genetic clustering. Additionally, no significant difference was found when comparing between governorate of birth and of residence until 15 years.