A woman aged 66 years, with a history of nodal osteoarthritis, presented with cutaneous nodules and flexion contractures of her fingers. Laboratory studies yielded normal results, including inflammatory markers, serum uric acid, rheumatoid factor, cyclic citrullinated peptide antibody, antinuclear antibody, and antibodies to extractable nuclear antigens. Radiographs of the patient’s hands showed an erosive arthropathy. A biopsy from the cutaneous nodule on the left second finger showed dense dermal fibrosis, loss of elastic fibres, and immunoreactivity for smooth muscle actin characteristic of myofibroblasts. What is the most probable diagnosis?
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