Is pigmented villonodular synovitis of the knee hereditary?

Q: My sister just emailed me that she has a condition called pigmented villonodular synovitis of the knee. What is this? Is it hereditary?

A: Pigmented villonodular synovitis (PVNS) is a benign disease of the joint synovium. Benign in this case means that the condition is confined to the area of involvement. It doesn't spread or travel to other parts of the body. It does not cause death but disability is possible. The synovium is the layer of soft tissue that lines the joint. It has a clear fluid that helps lubricate the joints.

Symptoms usually include joint swelling of a single joint (knee most often, hip, ankle, shoulder, elbow -- in that order) with pain and loss of motion. Pain and loss of motion get worse as the disease progresses. X-rays often show lytic lesions (bone eaten away).

But lytic lesions of the bone can be caused by cancer so an MRI and biopsy are required to make an accurate diagnosis. In the case of pigmented villonodular synovitis (PVNS), MRI findings are clear. This is because the tissue contains iron deposits called hemosiderin and the MRI signals clearly show these lesions. Synovial fluid can also be tested to provide another diagnostic clue.

The final confirming diagnostic "test" is surgery to open the joint and remove the tissue, a procedure called synovectomy. With open incision, the surgeon can clearly see the condition. A yellow thickened synovial tissue is usually visible. Tissue samples are sent to the lab to provide an examination of the cells, called a histology report. The pathologic histology also helps confirm the diagnosis.

The underlying cause of PVNS remains unknown. There are so few cases reported that large studies aren't possible. It seems to affect adults most often -- usually between the ages of 20 and 40. Men and women seem to be affected equally.

No family pattern has been reported but there could be an unknown inherited factor contributing to this condition. At this point, there is more we don't know about the condition that we know. If you start to develop joint pain of unknown cause with swelling and limited motion, don't hesitate to see a physician for an examination and evaluation. Early diagnosis and treatment can help prevent painful loss of motion and long-term damage to the joint.

Reference: Samia Mansouri, MD, et al. Pigmented Villonodular Synovitis of the Elbow with a Fenestrated Fossa. In Current Orthopaedic Practice. March/April 2012. Vol. 23. No. 2. Pp. 151-154.

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