A female infant with medium-chain acyl-CoA dehyrogenase (MCAD) deficiency who was diagnosed with Rett syndrome at 3.5 years is reported from Twenteborg Hospital, Almelo, and Wilhelmina Kinderziekenhuis, Utrecht, The Netherlands. At 13 months her development was normal. By 20 months she could not walk, her language development had ceased, and tremor with loss of purposeful hand movements was noted. At 30 months she had hypotonia, increased tremor and “handwashing” movements. At 3 years she was mentally retarded with autistic features, and the EEG showed bilateral spikes and spike wave activity and a slow waking background rhythm. The head circumference was at the 98th percentile from birth to 17 months and 50th percentile at 52 months. Four additional Rett syndrome patients had normal lymphocyte MCAD assays. 
COMMENT. The authors found no reason to propose a causal relationship between MCAD deficiency and Rett syndrome.
A controlled study of an oral opiate antagonist, Naltrexone, in 25 patients with Rett syndrome at the University of Alabama, Birmingham, AL, and other centers, showed a beneficial effect on respiratory irregularities and improved oxygenation but negative effects on development measured by Bayley scales . The hypothesis that naltrexone may be beneficial in Rett syndrome followed from reports of elevated levels of B-endorphins in the CSF of Rett syndrome patients. Further, the intraventicular administration of endorphins in animals produces naloxone-reversible signs similar to those of Rett syndrome.