Gene localization in the Snyder-Robinson syndrome

A family described as non-specific XLMR by Snyder and Robinson was re-evaluated 23 years later. Clinical and DNA studies were conducted on 17 family members; 6 affected males, 3 carrier females, and 8 normal males. All carrier females were clinically normal and the pattern of inheritance was clearly X-linked. Initial localization studies indicated linkage to the region near the DMD locus in Xp21.22. Further analysis focused on this region using (CA)n repeat polymorphisms for the dystrophin gene and for two markers distal to the gene. The dystrophin markers detected recombination across the entire gene, making it unlikely that the DMD locus was involved in the Snyder-Robinson syndrome. Normal dystrophin staining in a muscle biopsy in one affected male confirmed this observation. Multipoint analysis also indicate that the SRS (Snyder-Robinson Syndrome) locus was distal to DMD, and located near locus DXS41 (lod score = 4.00 at theta = 0.00). The presence of mild to moderate mental retardation, asthenic body build, diminished muscle bulk, nasal speech, high narrow/cleft palate, long thin fingers and great toes and mild to severe scoliosis permitted the delineation of a specific syndrome associated with this previously non-specific disorder. It is important, therefore, to recognize that today`s {open_quotes}non-specific{close_quotes}more » family may be tomorrow`s syndrome.« less