Klinefelter syndrome and associated Fragile‐X syndrome

. During screening of male individuals for Fragile‐X syndrome in a residential facility for persons with mental retardation, the authors found a 21‐year‐old profoundly retarded man who displayed facial features and behaviour suggestive of Fragile‐X syndrome. The chromosome analysis revealed 47, fra(X)(q27)fra(X)(q27)Y. His physically and intellectually normal sister had 14% of X chromosomes with a fragile site. Her two sons, who were subsequently examined, were found to have Fragile‐X syndrome. Thus, the identification of Fragile‐X syndrome in the proband during the screening process of a large institution led to the investigation of the proband's family and the subsequent diagnosis of Fragile‐X syndrome in the proband's two nephews. The ascertainment of the two affected boys permitted prompt introduction of early intervention and special education services. Genetic counselling of other at‐risk family members was carried out.