Objective:

NA

Background:

Mononeuritis multiplex (MM) is a rare but severe manifestation of systemic vasculitis resulting from ischemic injury to multiple peripheral nerves. Early recognition and aggressive immunotherapy are crucial to prevent irreversible damage. We report a case of small-vessel vasculitis presenting as rapidly progressive mononeuritis multiplex with dermatologic and systemic features, highlighting the diagnostic complexity and therapeutic value of prompt corticosteroid treatment.

Design/Methods:

A 50-year-old man with no prior medical history presented with rapidly progressive bilateral hand and foot weakness, distal sensory loss, and burning pain, more pronounced on the left side. Within one week, the weakness evolved in an asymmetric, stepwise pattern affecting all extremities. He also developed a non-pruritic purpuric rash with livedo reticularis, fever, night sweats, fatigue, and 10-pound unintentional weight loss. Neurologic examination revealed distal weakness (4/5), sensory ataxia, and diminished reflexes, with preserved coordination and gait.

Extensive laboratory testing ruled out infectious, hematologic, and autoimmune mimics. Nerve conduction studies showed an asymmetric distal axonal sensory-motor polyneuropathy consistent with MM. A nerve biopsy demonstrated ischemic and vasculitic changes, confirming small-vessel vasculitis. A concurrent skin biopsy showed thromboembolic coagulopathy and infarction.

Results:

High-dose intravenous methylprednisolone led to rapid improvement in motor and sensory function and marked resolution of neuropathic pain. The rash also improved significantly. The patient was transitioned to oral prednisone taper and later started on cyclophosphamide for long-term immunosuppression. At three-month follow-up, his strength improved to 4+/5 with recovery of daily function.

Conclusions:

This case underscores the importance of early recognition of vasculitic neuropathy as a cause of mononeuritis multiplex. A multidisciplinary approach and timely initiation of corticosteroids and immunosuppressive therapy are essential to prevent permanent neurological deficits and improve long-term outcomes.