Risk estimates for developing motor neurone disease in first‐degree relatives

Abstract

Patients with motor neurone disease resident in the three counties of South Glamorgan, Mid Glamorgan and Gwent (total population 1,394,400) from 1/11/91 to 31/12/92, were ascertained through general practitioners and neurology department records: 62 out of 71 (51 male, 20 female) index cases ascertained agreed to be visited. These individuals were clinically reviewed, had a detailed family history taken and, after discussion, had a blood sample taken for testing for the X-linked bulbospinal muscular atrophy mutation. The period prevalence of motor neurone disease was 5.02/100,000 with a mean age of onset of 59.4 (S.D. 12.9) years. One 66-year-old male was found to have the X-linked bulbospinal muscular atrophy mutation. A single, definite first-degree relative pair was identified, of whom only one was included in the data. The index cases had a total of 131 offspring and 173 siblings. The risk estimates, by current age, for these first-degree relatives of patients with apparently sporadic motor neurone disease decreased from 1 in 85 at age 20 years to 1 in 1683 at age 80 years. These estimates require confirmation in an independent sample, as they are based on a single "event".