Rheumatoid Arthritis — SCE Rheumatology MCQ

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A 48-year-old man with established rheumatoid arthritis has developed a firm, painless subcutaneous nodule over the posterior heel at the level of the Achilles tendon, where his footwear exerts pressure. He is anti-CCP positive and has a rheumatoid factor titre of 256 IU/mL. What is the most likely diagnosis?

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Correct answer: E — Rheumatoid nodule

This is a rheumatoid nodule, a characteristic extra-articular manifestation of rheumatoid arthritis. These are typically firm, painless subcutaneous lesions occurring at pressure or friction sites and may involve the Achilles region. Strong seropositivity, particularly a high rheumatoid factor titre, further supports the diagnosis. Histologically, rheumatoid nodules show central fibrinoid necrosis surrounded by palisading histiocytes. A ganglion is usually a fluctuant cyst arising near a joint or tendon sheath. A gouty tophus represents monosodium urate deposition and is usually supported by gout or crystal evidence. Calcinosis cutis consists of calcium deposits, often associated with systemic sclerosis or dermatomyositis. Tendon xanthomas cause nodular or fusiform tendon thickening and suggest an inherited lipid disorder rather than an RA extra-articular manifestation.

Reference: Drosos GA, Zikou AK, Voulgari PV, Drosos AA. Extensive Subcutaneous Rheumatoid Nodules Reflecting High Burden of Disease Activity. Mediterranean Journal of Rheumatology. 2026;37(2):427-430. https://pubmed.ncbi.nlm.nih.gov/42368981/