Erosive osteoarthritis (EOA) is considered to be a rare subset of osteoarthritis (OA) characterised by destructive changes involving the proximal interphalangeal and distal interphalangeal joints.^1–3 Laboratory findings are usually negative even though a slight increase of erythrocyte sedimentation rate may occur.^2,3 Radiologically, central erosions and the “gull wing” deformity characterise the disorder.⁴ Synovial pathology shows changes consistent with both rheumatoid arthritis (RA) and OA.^1,2 Histological examination of synovium from patients with EOA joints shows lining cell hyperplasia, lymphocytic infiltration, and pannus formation, features indistinguishable from those of RA.¹

The relationship between EOA and classical OA is controversial, as some authors consider it to be a separate disease entity, some regard it as one end of the …