Cutis verticis gyrate thickens the scalp into folds and furrows. (Image credit: The New England Journal of Medicine)

A 21-year-old man's head looks like the surface of a brain because of a rare condition that forms folds and furrows in his scalp.

The Brazilian man, whose name has not been made public, first noticed the condition two years ago, according to a case study published in this week's New England Journal of Medicine. After a biopsy ruled out cancer and inflammatory disease, he was diagnosed with cutis verticis gyrate - a rare disease that thickens the scalp.

"It can be associated with some rare genetic conditions, but most commonly occurs by itself," said Dr. Josh Zeichner, assistant professor of dermatology at Mount Sinai Medical Center in New York City, adding that most cases of cutis verticis gyrate occur in men soon after puberty.

The limited data on cutis verticis gyrate suggests an incidence of about 1 in 100,000 people, according to Zeichner. In the case of the man from Brazil, it was made more visible by his short hair.

"Treatment is mainly an aesthetic issue," he said, suggesting plastic surgery could be done to smooth out the scalp's "brainy" or "puzzle-like" appearance. "But you need make there are no associated medical conditions and take care that no bacteria or yeast grow within the furrows."

Because the man had no associated disorders and the condition didn't bother him cosmetically, he did not undergo treatment, according to the study.