Scleroderma-Like Skin Changes and Multifocal Muscle Thickening in a Patient with Diffuse Large B-Cell Lymphoma: A Case Report.

Background: Paraneoplastic rheumatic manifestations may precede the diagnosis of an occult malignancy and closely mimic primary autoimmune connective-tissue diseases. Scleroderma-like manifestations have rarely been reported in association with lymphoid malignancies, including diffuse large B-cell lymphoma (DLBCL). Case Presentation: A 47-year-old woman presented with progressive skin thickening, difficulty walking, reduced appetite, and weight loss. She had been diagnosed with scleroderma by an outside physician in early 2024 and had been treated with methotrexate 15 mg once weekly. Physical examination revealed facial skin tightening, sclerodactyly, skin induration extending to the wrists and elbows, and asymmetric thickening of the right neck, forearm, and thigh muscles. Pruritic migratory annular plaques were observed on the trunk and resolved spontaneously within two weeks, clinically suggesting an erythema annulare centrifugum-like eruption. Raynaud phenomenon was absent, antinuclear antibody testing was negative, and cervical and axillary lymphadenopathy was present. Computed tomography demonstrated multiple destructive osteolytic lesions in the lumbar vertebrae. Neck magnetic resonance imaging showed edema-like T2 hyperintensity involving the sternocleidomastoid muscle and adjacent tissues without contrast enhancement. Biopsy of a vertebral lesion revealed DLBCL, with tumor cells positive for leukocyte common antigen and CD20 and a Ki-67 proliferation index of approximately 80%. The patient was started on standard first-line R-CHOP immunochemotherapy but died in the intensive care unit after the first treatment administration, precluding assessment of treatment response and longer-term follow-up. Conclusion: This case illustrates an unusual presentation of DLBCL accompanied by scleroderma-like cutaneous changes, multifocal muscle thickening, and an annular eruption. The simultaneous absence of Raynaud phenomenon and antinuclear antibodies, together with constitutional symptoms, lymphadenopathy, asymmetric soft-tissue abnormalities, and destructive bone lesions, should prompt reconsideration of presumed systemic sclerosis and evaluation for an underlying malignancy. Although a paraneoplastic association was strongly suspected, it could not be confirmed because the patient died after the first treatment administration, precluding assessment of the rheumatic manifestations after lymphoma-directed therapy.