Incidence, prevalence, and gene frequency studies of chronic childhood spinal muscular atrophy.

TLDR

The study surveyed all cases of chronic childhood spinal muscular atrophy in north‑east England to determine gene and carrier frequencies, incidence, and prevalence. The authors used a segregation‑analysis method to estimate the autosomal recessive gene frequency despite dominant new mutations or phenocopies. Incidence was 1 in 24,100 live births, prevalence 1.20 per 100,000, gene frequency 0.0055, and carrier rate about 1 in 90.

Abstract

A total population study of chronic childhood spinal muscular atrophy (arrested Werdnig-Hoffmann disease, Kugelberg-Welander disease, SMA type II and III) was undertaken in north-east England to establish gene and carrier frequencies, incidence, and prevalence. The incidence of this disease was 1 in 24 100 live births. Prevalence was 1.20 per 100,000 of the general population. A technique for estimating an autosomal recessive gene frequency in the known presence of dominant new mutations (or phenocopies), using data from a segregation analysis, is described. Gene frequency was in the range (0.00451 to 0.00659 (95% confidence limits), with a working estimate of 0.0055. Carrier rates for the autosomal recessive gene concerned were 1 in 76 to 1 in 111 (95%) confidence limits), with a working estimate of 1 in 90 for genetic counselling purposes.