Abstract

Fibroblastic rheumatism is a rare dermatoarthropathy characterized by cutaneous nodules primarily on the hands, symmetrical arthropathy that can progress to a severe erosive form, and Raynaud's phenomenon. Patients may also have skin nodules in other periarticular sites, sclerodactyly, and joint flexion contractures. Histopathology remains the key to diagnosis of this rare entity. We report the case of a 86-year-old male with a past medical history of myelodysplastic syndrome, seronegative inflammatory arthritis, and Raynaud’s phenomenon who presented with one year of progressive nodules of the bilateral palms and fingers. Exam demonstrated numerous 0.5-2 cm, skin-colored, firm, dome-shaped, subcutaneous nodules primarily of the palmar periarticular fingers. H&E-stained sections from an excisional biopsy contained diffuse dermal fibrosis with patchy aggregates of lymphohistiocytic inflammation around vessels. Fibrotic regions comprised proliferations of CD34-positive fibroblasts with bland spindle cell cytomorphology. CD68 highlighted the histiocytic infiltrate as well as exhibited partial immunoreactivity for the fibroblastic proliferation. Laboratory evaluation was notable for negative rheumatoid factor, anticyclic citrullinated peptide antibodies, and antinuclear antibodies by immunofluorescence with positive RNP antibody alone. Taken together, findings were most suggestive of fibroblastic rheumatism. Distinguishing from disorders with similar clinical presentation, including multicentric reticulohistiocytosis, rheumatoid nodules, nodular scleroderma, and palmar fibromatosis can be challenging, but diagnosis is made by histopathologic findings of a fibroblastic or myofibroblastic proliferation, thickened collagen, loss of elastin, and minimal inflammatory component in the appropriate clinical context. It behooves the dermatopathologist to be aware of this rare entity given its potentially aggressive course with indication for early therapeutic intervention.

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