Prevalence of autosomal recessive congenital ichthyosis: a population-based study using the capture-recapture method in Spain.

BACKGROUND Previous reports on the prevalence of autosomal recessive congenital ichthyosis (ARCI) were based on single source data, such as lists of members in a patient association. These sources are likely to be incomplete. OBJECTIVES We sought to describe the prevalence of ARCI. METHODS We obtained data from 3 incomplete sources (dermatology departments, a genetic testing laboratory, and the Spanish ichthyosis association) and combined them using the capture-recapture method. RESULTS We identified 144 living patients with ARCI. Of these, 62.5% had classic lamellar ichthyosis and 30.6% had congenital ichthyosiform erythroderma. The age distribution included fewer elderly patients than expected. The prevalence of ARCI in patients younger than 10 years, the best estimate as less subject to bias, was 16.2 cases per million inhabitants (95% confidence interval 13.3-23.0). According to the capture-recapture model, 71% of the patients were not being followed up in reference units, 92% did not have a genetic diagnosis, and 78% were not members of the ichthyosis association. LIMITATIONS The prevalence of ARCI in Spain and findings related to the Spanish health care system might not be generalizable to other countries. CONCLUSIONS The prevalence of ARCI is higher than previously reported. Many patients are not being followed up in reference units, do not have a genetic diagnosis, and are not members of a patient association, indicating room for improvement in their care. Data suggesting a reduced number of older patients might imply a shorter life expectancy and this requires further study.