WHERE HAVE ALL THE FRAGILE-X BOYS GONE

A four-year retrospective survey of individuals referred for fragile X testing to South East Thames Regional Genetics Service was carried ou t to determine the accuracy of clinical diagnosis of fragile X syndrom e among routine referrals for cytogenetic confirmation. 680 individual s from 565 pedigrees were tested for fragile X. Five affected males we re identified in previously unknown families and 17 new pedigrees were diagnosed. Using the accepted prevalence data, a total of 80 affected males would have been expected in this period. The most likely explan ation for the low diagnosis rate is failure of referral of affected ma les.