Severe destructive arthritis of the carpometacarpal joint: a diagnosis of exclusion case report.

We present a case of severe destruction of the thumb carpometacarpal joint (CMCJ) and surrounding structures on a background of osteoarthritis and Seronegative Rheumatoid arthritis. Imaging studies suggested a soft tissue lesion consistent with Pigmented Villonodular Synovitis (PVNS), Synovial Osteochondromatosis or Giant Cell Tumour (GCT). Due to the possibility of malignant transformation and deteriorating symptoms the mass was excised. Histological analysis of the lesion revealed severe degenerative disease with no evidence of malignancy or infection. This represents an atypical presentation of thumb carpometacarpal joint arthritis, which should be diagnosed once more sinister pathology has been excluded.