A novel deletion of the dystrophin S-promoter region cosegregating with mental retardation.

A contiguous deletion of the S-promoter/first S exon and its downstream exon 56 of the dystrophin gene was identified in a Japanese dystrophinopathy family in which two brothers and their half brother were affected. Characteristically, severe mental retardation cosegregated with the deletion even though they grew up in different environments. Furthermore, mild cerebral atrophy was observed by CT scan and MRI in the eldest brother.