314 - An unusual urgent case presenting to the EDX lab: Mononeuropathy monoplex

Case Diagnosis: ANCA associated vasculitis presenting with sciatic nerve infarct.

Case Description: A 30-year-old healthy physician assistant presented to the EDX lab for left leg pain. She had a recent hospitalization for presumed urosepsis with fever and pyuria but remained febrile on two broad-spectrum antibiotics with very high inflammatory markers (CRP 208 and leukocytosis. She afterwards developed sudden pain and tingling in the left lateral calf and posterolateral foot as well as amarousis fugax. On exam she was found to have weakness and sensory dysfunction in the sciatic nerve distribution and a diminished left ankle reflex. EDX showed decreased tibial and fibular motor amplitudes, sural amplitude, and abnormal spontaneous activity of the tibialis posterior and EHL. Because of the clinical suspicion for a systemic vasculitis and sciatic neuropathy with no cause, the diagnosis of evolving mononeuropathy multi (mono) plex was made. She was seen urgently by rheumatology, admitted, had a sural nerve biopsy confirming vasculitis and pulsed with cyclophosphamide.

Discussions: While many serious conditions present in the EDX lab, they are rarely truly urgent and time-sensitive. If further delays in diagnosis, referral, and treatment with cyclophosphamide occurred, the patient could have developed blindness due to inadequately treated vasculitis, renal failure from further renal infarcts, and further disability from mononeuropathy multiplex and nerve infarctions.

Conclusions: Sciatic neuropathy with no clear explanation can be the first evidence of mononeuropathy multiplex, which can be an early presenting sign of an aggressive systemic vasculitis, which may require urgent diagnosis, referral, and treatment to prevent progressive end-organ infarctions, leading to long-term disability. This condition should be on the short list of truly urgent neuromuscular conditions presenting to the EDX lab in which a delay of hours or days could significantly impact the patient's long-term function.