Why did this man have copper-colored rings in his eyes?

Copper-colored rings inside a man's eyes proved key to diagnosing a rare disease, according to a new report.

The 47-year-old man, who lives in India, went to the doctor after he experienced abdominal swelling for two months, according to the report, published Saturday (Sept. 25) in The New England Journal of Medicine. He had no known medical conditions, and he didn't drink alcohol or take medications or supplements, the report said.

During a physical exam, doctors noted he had swelling in his abdomen and feet, as well as a "postural tremor," which is a tremor that occurs when people try to hold a part of their body against gravity, such as holding an arm out straight, according to the National Institutes of Health (NIH). He also showed signs of mild cognitive impairment, the report said. 

What's more, an eye exam revealed golden-brown rings encircling his irises in both eyes.

Doctors determined that these markings were Kayser–Fleischer rings, which are caused by a buildup of copper in the cornea, the eye's transparent outer covering. 

Kayser–Fleischer rings are a sign of a rare condition called Wilson's disease. People with Wilson's disease have a genetic mutation that prevents them from removing excess copper, which leads to a buildup of copper in the body — often in the liver, brain and eyes, according to the NIH. The condition occurs in about 1 in every 30,000 people, according to the NIH. It is typically diagnosed between ages 5 and 35, though symptoms may appear earlier or later in life, according to the Mayo Clinic.

The accumulation of copper in the body can lead to liver, kidney and neurological problems; and the disease can be fatal if not treated, the Mayo Clinic says.

In the man's case, he had developed cirrhosis, or scarring of the liver, which is seen in up to 45% of people with Wilson's disease at the time of their diagnosis, according to the NIH. The man also underwent genetic testing to confirm he had Wilson's disease.

The man received a medication, known as a chelating agent, that removes copper from the body. He also started taking zinc, which helps prevent the intestines from absorbing copper, according to the NIH. Treatment for Wilson's disease is lifelong, since stopping treatment will lead to copper building up in the body again. The man was also placed on a list for a liver transplant due to his serious liver damage, the report said. 

Originally published on Live Science.