[Fragile X syndrome. Clinical analysis of 300 Chilean patients with unspecific mental retardation]

Fragile X syndrome is the most important cause of sex linked mental retardation and the second of chromosomal origin, after Down syndrome.

To apply the modified Hagerman score to patients with mental retardation and to relate clinical findings with cytogenetic and molecular diagnosis.

The modified Hagerman score was applied to 214 male and 86 female patients with mental retardation. The clinical variables in non fragile X and fragile X cases, determined by molecular and cytogenetic methods, were compared.

The score in 210 non fragile X males was 10.5 + 3.7 (range 3-23), compared to 21.4 + 2.1 (range 19 to 23) in the four fragile X patients. All fragile X patients had mental retardation, attention deficits, hyperactivity disorders, hand biting and poor visual contact. Hand biting, flapping and perserving speech were observed in a significantly higher number of fragile X males. Only one of 86 females had fragile X syndrome: Her most relevant findings were a long face and high forehead, an attention deficit, hyperactivity and poor visual contact. No clinical differences with other mentally retarded females were found.

Approximately 5% of institutionalized males with mental retardation have a fragile X syndrome.