Author’s reply

Dr Docken expresses the opinion that the patient under discussion did not suffer from pigmented villonodular synovitis (PVNS) but from rheumatoid arthritis. Although I do agree that rheumatoid arthritis has to be considered as a differential diagnosis, the described patient did not fulfil the 1987 revised criteria for the classification of rheumatoid arthritis.1-1 The patient did not suffer from morning stiffness in and around joints. She did have swellings of the MCP joints that were asymmetrical—that is, far more prominent on her left side; no signs of arthritis in these joints were present, however. The symptoms were not symmetrical. The patient did not have subcutaneous nodules, no rheumatoid factor was present in her serum, x rays of hands and feet did not show any erosions.

The patient presented in the department of traumatology, hand and reconstructive surgery with a fixed flexion deformity of her left MCP joints, which caused inability to open her hand properly. She did not present with typical symptoms of rheumatoid arthritis such as morning stiffness, tenderness or pain. Synovectomy of the second to fifth MCP joints and reconstruction of the extensor hood of the left hand was performed. The right hand showed discrete thickening of the MCP joints. No need for surgery was discovered there. After surgery the patient was referred to rheumatology. Here the discrepancy between the lack of typical symptoms and signs of rheumatoid arthritis and the severe and asymmetric ulnar deviation, both of which is very unusual, was noted. Because of this discrepancy it was decided to ask for the routinely performed histological evaluation of the operation specimen, which clearly stated that PVNS was present.

The second point Dr Docken raises is the evaluation and interpretation of the histological specimen. His concern is that there might have been no histiocytes present in the specimen. Jaffe, Lichtenstein, and Sutro described in 1941² the salient histological features of PVNS, which are deposition of haemosiderin and infiltration of histiocytes and giant cells in a fibrous stroma within the synovium of tendon sheaths and large joints. I agree that it is the fibrohistiocytic proliferation that is characteristic for the pathology of the PVNS. Lipid filled histiocytes, also called foam cells, are depicted in figure 2 of the paper together with giant cells and scattered lymphocytes.

The third issue Dr Docken discusses is the fact that diffuse PVNS tends to occur monarticular. The knee is the most frequent joint involved, followed by the hip and ankle. Infrequently, the diffuse form will present in the hand, shoulder, wrist, and vertebral. Bilateral forms do occur occasionally³ and polyarticular forms are rare.1-4 Recently an unusual case of multiple site involvement of PVNS in a child has been reported.1-5 The case presented in our paper belongs to the rare polyarticular forms of diffuse PVNS.