X-linked recessive torsion dystonia in the Philippines

The occurrence of an X‐linked form of torsion dystonia in the Philippines was demonstrated by the genetic and biochemical analysis of affected males and their relatives. Thirty‐six affected males were ascertained in 21 families by clinical neurologic evaluation. The mean age‐of‐onset of dystonia was 37.9 years with a range from 12 to 52 years. Neurologic symptoms began focally and progressed to either segmental or generalized involvement in all cases. Generalized dystonia developed in 78% of the patients after a mean duration of 6.8 years from the onset of symptoms. A family history of dystonia was elicited in 17 of the 21 kindreds, accounting for a total of 64 males and one possibly affected female, distributed among 224 individuals in 33 sibships. In 18 of the 33 sibships, 2 or more brothers reportedly had dystonia. There were 12 kindreds with a history of multigenerational dystonia. In those, only males of maternal ancestry were affected, and in 7 of these families, maternal grandfathers reportedly had dystonia. There were no instances of male‐to‐male transmission. Cytogenetic analysis did not show any X chromosome abnormalities in 4 affected propositi. Several secondary causes of torsion dystonia were excluded, including Wilson disease, aminoacidopathies, organic acidurias, oligosaccharidoses, and chronic hexosam‐inidase A and B deficiency. These findings substantiate the existence of an X‐linked recessive form of primary torsion dystonia.