Fitzhugh Mullan, a social activist physician and author who wrote about health-care inequities and his own experience as a cancer patient in his early 30s, died Nov. 29 at his home in Bethesda, Md. He was 77.

The cause was lung cancer, said a spokesperson for George Washington University, where since 1996 he had been a professor of pediatrics and the management of health policy.

Before joining the university, Dr. Mullan served 23 years in the U.S. Public Health Service. He was an assistant surgeon general and director of the National Health Service Corps, which serves communities where health care is scarce or nonexistent. For three years, he practiced at a community medical clinic in New Mexico.

As a medical student at the peak of the civil rights movement, he spent a summer providing health care for medically ill-served and neglected black Mississippians in rural Holmes County. By his own count, he also took a half-dozen turns sitting on the steps of an African American church with a shotgun to protect it against night-riding marauders.

Later, as a medical resident at a city hospital in New York’s South Bronx, he helped organize a protest “bill burning” in the emergency room by moneyless patients who believed they had received excessive medical bills. Dr. Mullan and other residents were threatened with firing, but hospital authorities backed down after the New York news media covered the protest.

The son and grandson of doctors, Dr. Mullan described himself as having been “raised in comfort” in a New York family accustomed to the perquisites of an establishment class. But as a medical caregiver in New York, Mississippi, Chicago and elsewhere, he learned early that patients with no money and low social standing often received substandard medical care or none at all.

He wrote about medical injustice in a 1976 book, “White Coat, Clenched Fist: The Political Education of an American Physician,” which would become the professional manifesto of his career.

Among the white-coated aspiring doctors at the time, he later observed, “there was a sardonic comment often applied to colleagues departing for lucrative practices. ‘White follows green,’ the adage went, meaning that doctors went where the money was.”

While at GWU, Dr. Mullan was a writer and editor at the health policy journal Health Affairs. In his column, Narrative Matters, he often reflected on a system that, decades into his career, he considered still broken in its treatment of the disadvantaged.

One column from 2009 noted his work at a community medical clinic in Northwest Washington, where many of his patients were undocumented arrivals to the United States from Africa, Central America and Asia.

“These new Americans were all outside the established medical system,” he wrote. “They construct buildings, staff restaurants, and clean offices and homes but have no legal standing, and certainly no health coverage. The economy welcomes them, but the health system does not.”

Fitzhugh Seumas MacManus Mullan, known as “Fitz,” was born in Tampa on July 22, 1942, and grew up in New York City. His mother, Mariquita, was a poet and daughter of the Irish storyteller Seumas MacManus.

He graduated from the private Pomfret School in Connecticut in 1960, from Harvard in 1964 and from the University of Chicago’s medical school in 1968.

At 32, while working in New Mexico, Dr. Mullan was diagnosed with cancer deep within his chest, and he spent three years undergoing surgeries, chemotherapies and radiation therapies. He wrote about his ordeal in “Vital Signs: A Young Doctor’s Struggle with Cancer” (1982), which a reviewer for Kirkus Review found “riveting in its detail, moving in its candor.”

“He doesn’t spare us the calamities: the initial routine biopsy turned into a major, life-threatening operation when a large blood vessel was cut, necessitating open-chest surgery, massive blood transfusions, and a prolonged stay in an intensive care unit on a respirator,” the critic wrote.

“There followed severe radiation burns, extreme debilitation from chemotherapy, and a second, four-month-long hospital stay involving plastic-surgery procedures to repair treatment-induced deformities,” the reviewer added. “[Mullan’s] own assessment is that he was not a paragon of positive thinking.”

He expanded on some of the themes of his book in a 1985 New England Journal of Medicine article, “Seasons of Survival: Reflections of a Physician with Cancer.”

“Yes, beating the disease is important,” he wrote in the medical journal. “But you’re like Humpty-Dumpty. . . . You can’t be put back together again the way you were.”

His lungs had been compromised. He was worried about his sexual adequacy. He no longer wore short-sleeve shirts because he had scars on his arms where his skin had been removed to patch the radiation burns on his chest.

Most treatment plans, he added, “rarely address the psychosocial problems of reentering the active world . . . a common failure by doctors to think beyond a medical cure.”

What was needed, Dr. Mullan wrote, was a cancer “alumni association,” which he helped form in 1986 as the National Coalition for Cancer Survivorship. He later served as president and board chairman.

His first marriage, to Judith Wentworth, ended in divorce. Survivors include his wife of 13 years, Irene Dankwa-Mullan of Bethesda; three children from his first marriage, Meghan Mullan of Bethesda, Caitlin Crain of San Rafael, Calif., and Jason Mullan of Rockville, Md.; a stepdaughter, Perpetua Buadoo of Bethesda; a sister; a brother; a half brother; and four grandchildren.

While at GWU, Dr. Mullan continued focusing on issues of health-care equity and helped establish social justice as an important facet of medical education. He also published a book on the history of the U.S. Public Health Service and led a five-year study of medical schools in sub-Saharan Africa.

He was said to have been an avid sports fan — “always rooted for the underdog,” said his sister, Quita Mullan.