[Fragile X-syndrome and mental retardation].

Two cases of fragile X-syndrome are presented. Both boys had a family history of learning disability. This syndrome is the most common cause of inherited mental retardation. There are few dysmorphic features in childhood, but in puberty 80% of persons with this syndrome develop macro-orchidism, as presented in our second case. Some of the cases may have large ears, with no folding pinnea (simple pinnae). They may also have long faces, and a prominent forehead and chin. A characteristic of the condition is behavioural dysfunction, including hyperactivity and autism. The author discusses difficulties diagnosing the condition, both clinically and by specialized chromosome analysis.