Unusual Urgent Case Presenting to the EDX Lab: Mononeuropathy Monoplex.

Vasculitis presenting with sciatic nerve infarction is a rare and potentially urgent neuromuscular condition requiring timely diagnosis and intervention. We present the case of a previously healthy 30-yr-old female patient who developed sudden-onset left leg pain, tingling, and sensory deficits after hospitalization for presumed urosepsis. Examination revealed weakness and sensory dysfunction in the sciatic nerve distribution, and electrodiagnostic studies showed an axonal sciatic neuropathy. Given her amaurosis fugax, persistent fever, and elevated inflammatory markers, a diagnosis of emerging mononeuropathy multiplex due to systemic vasculitis was suspected. Sural nerve biopsy confirmed vasculitis, and treatment with cyclophosphamide was initiated. Delays in diagnosis or treatment of this condition may have resulted in irreversible disability and even death. This case underscores the importance of considering vasculitis in patients presenting with an unexplained focal mononeuropathy in the proper clinical context and highlights the need for urgent diagnosis and referral to prevent progressive end-organ damage and disability.