RETT VARIANTS - A SUGGESTED MODEL FOR INCLUSION CRITERIA

A model for the clinical delineation of atypical cases of Rett syndrom e is presented. It is based on the presence, at age greater than or eq ual to 10 years, of combined clusters of at least 3 of 6 primary crite ria and at least 5 of 11 supportive manifestations appearing through c hildhood with advancing age. The model was applied to 16 mentally reta rded females, aged 11-47 years (median: 23) who were considered to man ifest atypical variants of the syndrome (8 formes frustes, 6 late regr ession, 2 congenital variants). Two of the 16 patients had an early se izure history as the initial abnormality. In parallel, the number of s upportive manifestations in a series of 41 females over 10 years of ag e with classic Rett syndrome are given. The differentiating power was tested on 8 patients with a chromosome-verified Angelman syndrome. It is concluded that the model applied here has the capacity to identify and distinguish Rett syndrome variants of different types, to sift out other developmental disorders in routine clinical work, and to have p otential as a useful research tool.