Age at onset curves of retinitis pigmentosa.

OBJECTIVE To calculate age at onset curves of retinitis pigmentosa (RP) to resolve the difficulty in calculating the recurrence risk in a family. Retinitis pigmentosa is a common hereditary retinal disease that leads to blindness. It is a slow-onset disease, and family members of patients sometimes develop RP later. METHODS We studied 370 patients with typical RP. The age at onset was defined as when the patient's RP was diagnosed by an ophthalmologist. After confirmation that the age at onset came from normal distribution, we drew the age at onset curves. RESULTS The average age when patients were diagnosed with RP was 35.1 years, and the median age was 36.5. The onset ratio straightly increased with age until 65 years, so the onset ratio was relatively low at young ages. CONCLUSIONS The age at onset curves are quite simple and useful tools that facilitate counseling at an RP clinic. Without them, the recurrence risk would be misleading.