On the genetics of the Rett syndrome.

Ever since its recognition as a separate disease, the Rett syndrome has been reported to afflict girls only. For this reason, heredity has consistently remained at the forefront of discussions regarding putative causes. On account of the gravity of the disorder and the want for adequate therapy, the clarification of its genesis is of great practical importance in consideration of the possibility of descendants. J Wahlström reports a breakpoint at Xp22 in two sisters with the disease and in their healthy mother. This finding is questionable as being typical of the syndrome in light of recent chromosomal findings. In addition to Wahlström's two-step-mutation hypothesis, an earlier suggestion of an X-chromosomal dominant new mutation is under discussion again. Further genetic findings are expected from a yet-to-be-completed interpretation of all relevant data hitherto observed in approximately 160 probands and their families.