Kilmer S. McCully, a pathologist at Harvard Medical School in the 1960s and ’70s whose colleagues banished him to the basement for insisting — correctly, it turned out — that homocysteine, an amino acid, was being overlooked as a possible risk factor for heart disease, died on Feb. 21 at his home in Winchester, Mass. He was 91.
His daughter, Martha McCully, said the cause was metastatic prostate cancer. His death was not widely reported at the time.
Still debated today, Dr. McCully’s theory was that inadequate intake of certain B vitamins causes high levels of homocysteine in the blood, hardening the arteries with plaque. The idea challenged the cholesterol-focused paradigm backed by the pharmaceutical industry.
Dr. McCully didn’t think cholesterol should be ignored, but he thought it was malpractice to disregard the significance of homocysteine. His bosses at Harvard disagreed. First, they moved his lab below ground; then they told him to leave. He struggled to find work for years.
Dr. McCully, fashioning himself as a microbe hunter akin to Louis Pasteur, stumbled on homocysteine in the late 1960s at a medical conference in Boston. There he learned about homocystinuria, a genetic disease in which high amounts of homocysteine are found in the urine of some developmentally disabled children.
Presenting the case of homocystinuria in a 9-year-old girl, doctors mentioned that her uncle had died from a stroke in the 1930s, when he was 8 and had the same disease. “How could an eight-year-old have died the way old people do?” Dr. McCully wrote, with his daughter, in “The Heart Revolution” (1999).
When Dr. McCully tracked down the autopsy report and tissue samples, he was astounded: The boy had hardened arteries, but there was no cholesterol or fat in the plaque buildup. A few months later, he learned about a baby boy with homocystinuria who had recently died. He also had hardened arteries.
“I barely slept for two weeks,” he wrote.
In 1969, Dr. McCully published a paper about the cases in The American Journal of Pathology. The next year, in the same journal, he described what happened after he injected rabbits with high doses of homocysteine. “The aortas of all 13 of the animals injected with homocysteine were moderately thickened,” he wrote, “compared to the controls.”