Case report. Elbow monoarthritis revealing B cell non-Hodgkin's lymphoma.

Skeletal involvement is described in 25% of patients with non-Hodgkin's lymphoma, typically as secondary, rarely as primary lymphoma of bone. Joint infiltration is very rare and monoarthritis can be a secondary synovial reaction to adjacent bone disease or direct synovial involvement. We describe an unusual case of monoarthritis of the elbow in a middle-aged man without signs and/or symptoms associated with malignancy and with no previous rheumatic disease. Synovial biopsy revealed a diffuse infiltrate of large atypical lymphocytic B cells diagnosed by morphological and immunohistochemical findings as a malignant lymphoma. Staging procedures including total body CT scan, bone marrow biopsy, technetium-99m methylene diphosphonate bone scintigraphy were normal. We discuss the case and the review of literature and suggest that in the evaluation of patients with an unclassified arthritis, synovial or bone biopsy should be strongly considered.