Screening for fra(X)(q) in a population of mentally retarded males.

Among 242 institutionalized mentally retarded males in Northern Germany screened for fra(X)(q), 15 (6.2%) with severe mental retardation expressing fra(X)(q) were detected. One patient displayed Klinefelter's syndrome in addition. All fra(X)(q) males showed the typical facial signs, but three of the adults did not express macroorchidism. A preliminary estimation of an overall frequency of 1:2000 males for the fra(X)(q) condition is suggested.