When a 38-year-old man complained of pain in his knee joints, his doctor conducted the usual tests and found a tendon tear.

A surgery was performed by opening the skin and repairing the tendon. His doctor thought that was the end of the matter. But a year later, the man began experiencing pain in the hips which spread to his knees. Six months ago, the pain became so severe that he could not carry out his daily activities.

A series of tests revealed the man, a native of Nellore, suffered from a rare condition called ochronotic arthritis, a condition caused by genetic deficiency of an enzyme called homogentisate oxidase.

Deficiency of the enzyme leads to metabolic disorders and, though not life-threatening, could lead to permanent disability. Patients may experience excessive pain in the joints, blackening of cartilages, tissues and pigmentation of the eye. Some patients may develop black patches in the mouth or their urine turns black.

“We repaired the tendon and did not go all the way to the cartilage, so we could not diagnose the condition initially,” said orthopaedic surgeon Madan Mohan Reddy who performed the first surgery on the Nellore patient.

Later, successive tests led to the diagnosis, said the doctor who is attached to Apollo Hospitals. When he found the cartilages had turned black, he realised the patient suffered from a rare genetic disease.

“World over, there are only 54 reported cases of the disease,” Dr. Reddy said.

The patient was given an implant for his knee. Though the blackened tissues have been removed, Dr. Reddy said the patient could develop a similar condition in some other part of the body at a later date.

One way to delay the progression of the condition is by increasing intake of vitamin C-rich foods such as tomatoes and Indian gooseberries. Those prone to the condition should avoid lobsters, tuna fish and almonds.

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