A dark spot over President Franklin D. Roosevelt's left eyebrow has intrigued medical researchers.

When President Franklin D. Roosevelt died unexpectedly on April 12, 1945, in Warm Springs, Ga., the White House lost no time announcing a cause of death.

The 63-year-old president, the shocked and grieving nation was told, had died of cerebral hemorrhage. (“Last Words,” read a front-page headline in The New York Times: “‘I Have a Terrific Headache.’”)

That Roosevelt died of a stroke is undisputed. But what caused it is a medical mystery that has persisted to this day, a mystery heightened by the secrecy in which he, his aides and his doctors always insisted on shrouding his health.

Now, a new book — “FDR’s Deadly Secret,” by a neurologist, Dr. Steven Lomazow, and a journalist, Eric Fettmann (PublicAffairs) — revives an intriguing theory.

Look closely at Roosevelt’s portraits over his 12-year presidency. In his first two terms, there is a dark spot over his left eyebrow. It seems to grow and then mysteriously vanishes sometime around 1940, leaving a small scar.

What was it?

Was the spot a harmless mole? Or a cancerous melanoma that spread to contribute to, or even cause, his death? Melanomas, after all, are known for causing strokes from bleeding when they spread to the brain.

This hypothesis is not new. In 1979, Dr. Harry Goldsmith, then a surgeon at Dartmouth, wrote a widely publicized medical journal article focusing attention on the possibility that the spot was a melanoma. (I wrote an article about it at the time.) In 2007, after more medical sleuthing, Goldsmith published a book, “A Conspiracy of Silence” (iUniverse), fleshing out the theory.

What is different in the new book is the categorical claim that the killer was a melanoma that “metastasized to his brain, causing the growing tumor that would take Roosevelt’s life a mere six weeks later.”

But no matter how confidently the authors may assert it, the claim is still speculation — unproved and far from convincing.

Roosevelt’s death was shocking in part because the White House and his doctors had kept secret how sick he was. For example, though it was widely known that he had developed polio in 1921 at age 39, he and his aides disguised the fact that he could not walk unaided and used heavy metal braces to stand on paralyzed, withered legs. He used a wheelchair and demanded that photographers not show his disabilities.

Kept quiet

His terminal illness came during wartime, and in an era when leaders’ health and other personal matters were considered strictly private.

With rare exceptions, journalists were complicit. They did not probe the obvious clues they saw as the president’s appearance deteriorated.

Over his last year, for instance, he lost about 30 pounds. His doctors attributed it to a poor appetite from a prescribed diet; Lomazow and Fettmann contend he became scrawny from a spreading melanoma.

The authors point out that Turner Catledge, then a Washington correspondent for The New York Times and later its executive editor, did not report how awful Roosevelt looked during an interview at the White House in 1944, months before his nomination to an unprecedented fourth term.

Roosevelt was gaunt and glassy-eyed, Catledge wrote many years later; his jaw drooped, and he lost his train of thought. Others witnessed similar episodes; in an interview, Lomazow attributed them to a type of seizure often associated with strokes.