Prevalence and Genetics of Leber Hereditary Optic Neuropathy in the Danish Population.

PURPOSE: In Denmark, the occurrence of Leber hereditary optic neuropathy (LHON) has continuously been monitored since 1944. We provide here a summary of 70 years of data collection including registered lines and subjects by the end of 2012. METHODS: Affected individuals were identified from a national register of hereditary eye diseases at the National Eye Clinic (NEC), a tertiary low vision rehabilitation center for the entire Danish population. The assembling of LHON pedigrees was based on the reconstruction of published families and newly diagnosed cases from 1980 to 2012 identified in the files of NEC. Genealogic follow-up on the maternal ancestry of all affected individuals was performed to identify a possible relation to an already known maternal line. A full genotypic characterization of the nation-based LHON cohort is provided. RESULTS: Forty different lines were identified. The number of live affected individuals with a verified mitochondrial DNA mutation was 104 on January 1, 2013, which translates to a prevalence rate of 1:54,000 in the Danish population. CONCLUSIONS: Haplogroup distribution as well as mutational spectrum of the Danish LHON cohort do not deviate from those of other European populations. The genealogic follow-up reveals a relatively high turnover among families with approximately 15 newly affected families per century and the dying out of earlier maternal lines.