Pigmented Villonodular Synovitis
Pigmented Villonodular Synovitis (PVNS) is a benign condition in which the body’s synovium is inflamed and accumulates deposits of hemosiderin. Xanthomatosis and benign synovioma, also refer to PVNS.
There are two forms of pigmented villonodular synovitis, local and diffuse. The local form refers to one discreet area of the synovium being involved. In the diffuse form, the entire synovial lining of the joint is involved. Both forms often present with pain, swelling, and stiffness of a single joint. The symptoms are atraumatic, but often worsen with activity. Patients can also present with mild joint symptoms as above, but with a large soft tissue extension of the disease causing a palpable mass.
The diffuse form of PVNS is the most common, and reports indicate 2 cases per million people per year. Men are just as likely as women to have this diagnosis.
Pathology and pathophysiology
The local pathophysiology is related to the inflammatory response to the synovial hypertrophy. As in rheumatoid arthritis, the synovial mass can invade the adjacent bone and cause periarticular erosions. Inside the joint, the synovial mass can cause mechanical symptoms from the mass effect.
Grossly one can see diffuse or nodular yellow to brown synovium.
Under the microscope one will find a large number of stromal and fibroblast cells, hemosiderin deposits, macrophages filled with lipid, and multinucleated giant cells, lymphocytes, and plasma cells.
Diseases that present similarly to PVNS include advanced degenerative joint disease; rheumatoid arthritis; arthropathy caused by psoriasis, haemophilia, amyloid, etc; pagent’s disease of the bone, systemic lupus erythematosus, hemochromatosis, and synovial osteochondromatosis or hemangioma.
PVNS is largely considered a neoplastic process since its fast growth pattern, bone and joint erosion, and high recurrence rates mimic an oncologic process. New studies suggest it could be an inflammatory disease.
Radiographic and laboratory findings
Plain Films are not a good diagnostic tool for PVNS. It lacks both sensitivity and specificity. Only thirty percent of patients present with radiographic findings. Late stages of the disease look similar to that of osteoarthritis.
Bone Scan should demonstrate an increased uptake of radiotracer, but it is not commonly used for diagnosis.
CT Scan demonstrate hyperdense, hypervascular synovium.
MRI is the best imagining choice for PVNS. One can also see synovial masses with bone erosion, low signals on T1 and T2, joint effusions, and lesions that enhance with contrast. The low signal on both fluid and fat sensitive sequences is due to the hemosiderin deposition.
Lab tests are not usually preformed during this diagnostic process, but can be helpful ruling out rheumatologic disease.
Risk factors and prevention
With an unknown etiology there are no known risk factors or preventative methods.
Complete surgical excision of the involved synovium is the recommended treatment of PVNS. In this focal form this can be done with a limited surgical procedure either viw arthrotomy or arthroscopy. For the diffuse disease, a total synovectomy of the affected joint would be required.
Recurrence occurs less frequently in those with local disease, when compared to those with diffuse disease. Complications include local reoccurrence and progressive arthrosis requiring joint arthroplasty. Untreated disease usually leads to severe arthritis of the involved joints.
Understand that diagnosis often takes quite sometime, and that patients may be frustrated when they reach you. The impact of PVNS can be compared to osteoarthritis, and therefore patients may experience decrease in social and work activity levels.
Pigmented Villomodular Synovitis, Hemosiderin, Hemearthrosis, PVNS
Skills and competencies
A student should be able to acquire a patient history suggestive of arthritis, and recall that PVNS is in the differential.