Elevated CSF beta-endorphin immunoreactivity in Rett's syndrome: report of 158 cases and comparison with leukemic children.

Because some symptoms of Rett's syndrome are suggestive of excessive endogenous opioid activity, we measured the levels of beta-endorphin-like immunoreactivity in lumbar CSF from 158 affected female patients and from 13 female controls. The mean (+/- SE) control level of beta-endorphin immunoreactivity in CSF was 35.3 +/- 2.8 pg/ml (range, 23 to 48 pg/ml), whereas those with Rett's syndrome had a mean level of 95.3 +/- 3.6 pg/ml (range, 31 to 293 pg/ml). The levels of beta-endorphin immunoreactivity in initial CSF samples exceeded the control range in 90% of the patients with Rett's syndrome. The mean beta-endorphin immunoreactivity was also elevated in CSF from leukemic children (119.2 +/- 16.9 pg/ml; range, 40 to 159 pg/ml), relative to the control group. These results are consistent with the hypothesis that some symptoms of Rett's syndrome may be associated with excessive endogenous opioid levels in the CNS.