Serum melatonin kinetics and long-term melatonin treatment for sleep disorders in Rett syndrome

We studied the circadian rhythm of serum melatonin levels in two patients w ith classical Rett syndrome having severe sleep disorders; serum melatonin levels were measured before and during melatonin treatment using radioimmno assay. Patient 1 had a free-running rhythm of sleep-wake cycle from 3 years of age. At the age of 3 years, the peak time of melatonin was delayed 6 h compared to normal control and the peal; value was at the lower limit. Pati ent 2 had a fragmented sleep pattern accompanied by night screaming from 1 year and 6 months of age. At the age of 10 years, the peak time of melatoni n secretion was normal but the peak value was at the lower limit. These pat ients were given 5 mg melatonin orally prior to bedtime. Exogenous melatoni n dramatically improved the sleep-wake cycle in patient 1. In patient 2, ex ogenous melatonin showed a hypnotic effect but early morning awakenings occ urred occasionally. When melatonin treatment was stopped, the sleep disorde rs recurred and re-administration of 3 mg melatonin was effective in both p atients. The effect was maintained over 2 years without any adverse effects . These findings suggests that sleep disorders in patients with Rett syndro me may relate with an impaired secretion of melatonin. (C) 1999 Elsevier Sc ience B.V. All rights reserved.