Analysis of mitochondrial DNA from 15 children with Rett syndrome (RS) and 14 of their mothers is reported from the Department of Pediatrics, Beijing Medical University, China. Polymerase chain reaction amplification and single strand conformation polymorphism analysis showed mutations in region 2650-3000 encoding 16S rRNA of mtDNA in 13 patients with RS and 11 mothers. DNA sequence analysis and mismatch PCR results confirmed a point mutation (C —> T) at position 2835 in 7 patients with RS and in 6 of their mothers, that was absent in controls. 
COMMENT. Most cases of Rett syndrome are sporadic, but a few familial examples are reported. A maternal inheritance pattern suggests that mitochondrial DNA may be involved. The mutations observed in the mtDNA of patients with Rett syndrome and their mothers lends support to the hypothesis of a genetic basis for the disorder in some cases.
Japanese monozygotic female twins with Rett syndrome are reported from Fukuoka University, Japan . The two 28-year-old patients had discordant characteristics regarding seizures, scoliosis, and stereotypic hand movements in adolescence. The authors cite 7 pairs of monozygotic twins with RS reported in the literature, and 11 pairs of dizygotic twins, only one twin affected, always the female.