18q-mosaicism associated with Rett syndrome phenotype

Rett syndrome consists of a characteristic progressive encephalopthy in females. The cause of this syndrome is unknown. We present a patient with 18q‐mosaicism who, along with the characteristics of this autosomal deletion, also fulfills the clinical criteria for Rett syndrome. This may demonstrate heterogeneity within this as yet cinically defined syndrome. A thorough chromosomal analysis should be performed in suspected cases of Rett syndrome. © 1993 Wiley‐Liss, Inc.