Dr. Thomas J. Pekin Jr., 53, a clinical rheumatologist and internist who had taught at Georgetown University medical school since 1963, died of cancer June 8 at his home in Bethesda.

Dr. Pekin was an authority on the causes of arthritic inflammatory conditions. He was a past president of the District of Columbia Rheumatism Society and a director of the Georgetown University Arthritis Clinic. He was a member of the American Rheumatism Association.

In addition to his teaching and research, he served on the university's admissions and education committees.

Dr. Pekin was born in Chicago and reared in Washington. He was a graduate of Gonzaga College High School and earned his bachelor's and medical degrees at Georgetown University. He interned at D.C. General Hospital.

He was a medical flight officer with the Navy in the Pacific during World War II.

Survivors include his wife, the former Joan Wenger, two sons, Thomas J. III and James C., and two daughters, Terese J. and J. Kathleen Pekin, all of Bethesda; his parents, Dr. and Mrs. Thomas J. Pekin Sr. of Newport Beach, Calif.; two sisters, Terese Kathleen Walsh and Patricia E. Wylie, both of San Diego, Calif., and three brothers, Dr. James Pekin of San Dimas, Calif., P. Michael Pekin of Monterey, Calif., and Dr. Richard J. Pekin of San Diego.