OBJECTIVES: I. Determine dietary macronutrient intake in children with Rett syndrome and in healthy controls.

II. Measure sleeping and awake metabolic rates in various positions, i.e., reclining, sitting, and standing, by whole-room indirect calorimetry and isotope dilution.

III. Quantify activity patterns by time-motion studies using 24-hour activity records and 12-hour videotaping.

IV. Correlate 24-hour activity patterns with 24-hour heart rate telemetry and short-term oxygen consumption.

V. Estimate 24-hour fecal and urinary energy losses. VI. Determine body composition by clinical anthropometry, whole-body potassium counting, and total-body electrical conductance.

VII. Calculate apparent energy needs based on measurement of energy intake and expenditure.

PROTOCOL OUTLINE:

All participants undergo extensive nutritional and metabolic assessment with body composition evaluation. Studies include macronutrient intake, body fat, lean muscle mass, metabolic rate, and time-action studies; and 24-hour cardiac telemetry. Rett syndrome girls also receive a hemogram and hand x-ray.

PROTOCOL ENTRY CRITERIA:

Patients aged 5 to 18 with Rett syndrome Able to sleep and awaken alone