Dr. Mark M. Platt, 39, associate chairman of neurology at Children's Hospital and an associate professor of neurology, child health and development at George Washington University's medical school, died Monday of acute hepatitis at Georgetown University Hospital.

He also was a neurology consultant at Walter Reed Army Medical Center, the National Institutes of Health and the Montgomery County Health Department. Dr. Platt was the author of numerous technical works, and had particular interest in the genetic aspects of neurological disease.

Dr. Platt lived in Potomac and came to the area in 1972 when he joined the staff of Children's Hospital as assistant chief of neurology and director of the neurology and seizure clinics.

He was a native of Jamaica, N.Y. and graduated from the University of Vermont. In 1966, he received his medical degree from the Vermont Medical School in Burlington. He completed his pediatric training at Columbia Presbyterian Medical Center in New York City and was a resident in neurology at Boston City Hospital and Massachusetts General Hospital, before moving here.

Dr. Platt was a diplomate of the American Board of Pediatrics and the American Board of Psychiatry. He was a fellow of the American Academy of Pediatrics and the American Academy of Neurology, and was a member of the Child Neurology Society, the American Epilepsy Society and the American Society of Human Genetics. He served on the editorial review board of the Journal of Developmental and Behavioral Pediatrics and was a member of the medical advisory board of the Tuberculosis Association of America.

Survivors include his wife of 11 years, Janet Verner Platt of Potomac, and a brother, Dr. Alan Platt of San Francisco, Calif.

The family suggests that expressions of sympathy be in the form of contributions to the Mark Platt Pediatric Neurology Fund, c/o Children's Hospital National Medical Center, 111 Michigan Ave., Washington, D.C., 20010.