Dr. Kehl Markley III, 55, a medical director with the National Institute of Arthritis, Metabolism and Digestive Diseases, died Wednesday at his home in Bethesda after apparently suffering a heart attack.

A specialist in the treatment of burns, he had been with the U.S. Public Health Service, under whose jurisdiction the National Institutes of Health fall, since 1951.

Dr. Markley was born in Pennsburg, Pa. He was a graduate of Pennsylvania State College, where he was elected to Phi Beta Kappa, and from the University of Pennsylvania Medical School. He had served with the Army in World War II.

The U.S. Public Health Service sent Dr. Markley to Lima, Peru in 1951 to do research on the treatment of burns. He returned in 1956 and worked with USPHS in Philadelphia for two years before transferring to NIH here.

He is survived by his wife, Nena and two children, Sanford and Lena, all of the home; two other children, Pilar, of Silver Spring, and Richard, of Gaithersburg, and two sisters, Mary Lou Hendrix, of York, Pa., and Madelyn Kulp, of Reading. Pa.

The family suggests that expressions of sympathy be in the form of contributions to the Kehl Markley Memorial Fund at River Road Unitarian Church in Bethesda.