[Otosclerosis in populations living in northern Tunisia: epidemiology and etiology]

Otosclerosis is a hereditary disease frequently encountered in Caucasian populations (0.1 to 2% prevalence). In Tunisia, prevalence varies from 0.4% to 0.8%. The presence of a genetic factor associated with hormonal, biochemical or environmental factors, probably lead to variable expression of the otosclerosis according to age and sex. Mean age at onset of disease is 25 years (range 16-35 year) for 61.5% of affected women. In men this proportion is 50.2%. The incidence of otosclerosis is high in the 26-35 year age group. Our study showed that in northeastern areas of Tunisia, women in this age group were affected twice as often as men in this age group. This probably suggests that an endocrine mechanism is involved in disease etiology. However, in northwestern areas, there was no significant difference between the rates of otosclerosis between sexes. Geographical distribution of affected subjects according to the ethnic origin of their parents showed that the areas with the highest concentration of affected individuals were urban or seaside areas such as the gouvernorate of Nabeul. The frequency of otosclerosis was lower in rural areas and/or areas far from the seaside.