A can of red herrings.

Lymphomatoid granulomatosis is a rare disease. Anti-cyclic citrullinated peptide (anti-CCP) antibody is more commonly found in patients with rheumatoid arthritis and less frequently in some of the other rheumatic and non-rheumatic conditions. It is not recognized to be present in lymphoproliferative disease on its own. We report the first case of anti-CCP antibody positivity in lymphomatoid granulomatosis presenting with polyarthritis. This case illustrates the evolving nature of this disease and its characteristics at different stages leading to the challenge of an accurate diagnosis in the setting of a paraneoplastic polyarthritis.