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

Background: Fragile X syndrome is the most important cause of sex linked me ntal retardation and the second of chromosomal origin, after Down syndrome. Aim: To apply the modified Hagerman score to patients with mental retardat ion and to relate clinical findings with cytogenetic and molecular diagnosi s. Patients and methods: The modified Hagerman score was applied to 214 mal e 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. Results: 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 fou r fragile X patients. All fragile X patients had mental retardation, attent ion deficits, hyperactivity disorders, hand biting and poor visual contact. Hand biting, flapping and persevering speech were observed in a significan tly 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 diff erences with other mentally retarded females were found. Conclusions: Appro ximately 5% of institutionalized males with mental retardation have a fragi le X syndrome.