Paraneoplastic anti-SRP antibody positive immune-mediated necrotizing myopathy in a young female associated with lymphoma.

We report an exceptional case of immune-mediated necrotizing myopathy (IMNM) associated with anaplastic large cell lymphoma (ALCL). A 26-year-old female patient presented with subacute bilateral proximal muscle weakness and myalgia, highly elevated creatin kinase (CK), and seropositivity for anti-SRP antibodies. Tumor screening by FDG-PET/CT detected an enlarged axillary lymph node with high FDG uptake. Histology of the excised lymph node revealed ALCL, positive for ALK and CD30. Therapy with brentuximab, cyclophosphamide and doxorubicin resulted in complete remission of the lymphoma, additional treatment with oral steroids and repeated cycles of intravenous immunoglobulins led to improvement of muscle weakness and normalization of CK. 18 months after diagnosis the patient remains tumor free with mild to moderate residual axial weakness. A literature review of paraneoplastic anti-SRP antibody positive IMNM identified eleven cases of whom five had a tumor diagnosis within a ±3 years window. The majority of patients had different solid tumors except one with a hematological malignancy. Despite the rare association of anti-SRP antibody positive IMNM and malignancy, early extensive tumor screening was crucial for the management of our patient.