PREVALENCE OF FRA(X) IN THE COUNTY OF FUNEN IN DENMARK IS LOWER THAN EXPECTED

Population based cytogenetic fra(X) surveys have not previously been r eported from Denmark. In the present study we present an estimate of f ra(X) based on 1) information from the Danish Central Cytogenetic Regi stry of diagnosed fra(X) males of all age groups in all Denmark in the period 1980- 1992 and 2) a systematic cytogenetic fra(X) survey of 17 5 of 8-10-year-old children with special educational needs resident in a defined, demographically representative area of Denmark (the county of Funen). The study was performed in 1988-90 before the cloning of t he FMR-1 gene. In the county of Funen there were 7,837 male children i n the age group of 8-10 years. In the cytogenetic survey of learning d isabled children, no fra(X) positive was diagnosed. There were 99 regi stered males with fra(X) in all Denmark, equivalent to a prevalence of 0.04 per 1,000 males (confidence interval 0.032:1,000-0.048:1,000).Mo lecular fra(X) surveys of different, large populations are needed in o rder to estimate the frequency of fra(X) and clarify whether significa nt differences in prevalence exist in different populations. (C) 1994 Wiley Liss, Inc.