Paraneoplastic Myopathy as a Possible Initial Presentation of Sporadic Burkitt Lymphoma in an Immunocompetent Adult: A Case Report.

BACKGROUND: Burkitt's lymphoma (BL) is a highly aggressive B-cell non-Hodgkin lymphoma with rapid proliferation and early systemic dissemination. Neuromuscular manifestations are rare and are typically secondary to direct infiltration or metabolic complications. Paraneoplastic myopathy as the initial presentation of BL is exceedingly uncommon, particularly in immunocompetent adults. CASE PRESENTATION: We report the case of an immunocompetent adult male who presented with acute progressive proximal muscle weakness and markedly elevated creatine phosphokinase (CPK) levels. Extensive autoimmune, metabolic, and endocrine evaluations were unremarkable. Electrophysiological studies supported a primary myopathic process. Contrast-enhanced computed tomography revealed left axillary lymphadenopathy and splenomegaly without generalized lymphadenopathy. Excisional lymph node biopsy confirmed sporadic Burkitt's lymphoma with MYC rearrangement. Muscle biopsy was deferred due to rapid disease progression and the urgent need for oncologic treatment. The patient was treated with the Hyper-CVAD regimen combined with rituximab and central nervous system prophylaxis. Following chemotherapy, muscle strength improved rapidly, accompanied by a marked decline in serum CPK levels. CONCLUSION: This case highlights a rare paraneoplastic manifestation of Burkitt's lymphoma presenting as acute myopathy. Rapid clinical and biochemical response to chemotherapy supports a tumor-mediated mechanism. Clinicians should consider underlying hematologic malignancy in patients with unexplained myopathy and elevated muscle enzymes, as early diagnosis and prompt treatment may significantly improve outcomes.