TY - JOUR T1 - Incidence, prevalence, and gene frequency studies of chronic childhood spinal muscular atrophy. JF - Journal of Medical Genetics JO - J Med Genet SP - 409 LP - 413 DO - 10.1136/jmg.15.6.409 VL - 15 IS - 6 AU - J Pearn Y1 - 1978/12/01 UR - http://jmg.bmj.com/content/15/6/409.abstract N2 - 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. ER -