Friedreich's ataxia: an epidemiological study in Valencia, Spain, based on consanguinity analysis.

Epidemiological studies performed directly on the population show a prevalence of Friedreich's ataxia (FA) from 1 to 4.7 cases/100,000 inhabitants. An indirect epidemiological approach can be achieved using genetic methods like consanguinity studies to determine the frequency of a mutated gene and the incidence of certain diseases in the population. We obtained consanguinity data of a series of FA patients in Valencia, Spain and the figures on consanguinity in the general population that were estimated according to the Archive of Dispensations given by the Catholic church for consanguineous marriages. From these data, the frequency of the FA gene was calculated as 1/127. From these data, applying the Hardy-Weinberg principle, the frequency of the carriers was 1/64 and the incidence was 6.18/100,000 live births. Assuming a life expectancy of FA of 45 years, the prevalence was 3.83/100,000 inhabitants. These figures are in the same range as those obtained in population studies.