[Mononeuritis multiplex in a patient with cutaneous arteritis diagnosed by skin biopsy].

A 55-year-old man was admitted with paralysis of the left lower leg. He had purpura in the left lower extremity for three years, left calf pain for two years, and dysesthesia in the left plantar region and first toe for one year. A physical examination revealed livedo reticularis on the left leg and mononeuritis multiplex was diagnosed in the bilateral tibial and left peroneal nerve area. Anti-neutrophil cytoplasmic antibody was negative. A nerve conduction study showed decreased amplitude of compound muscle-action potential in the bilateral tibial and the left peroneal nerve, sensory nerve action potential in the bilateral sural nerve. A skin biopsy revealed inflammatory cells on blood vessel walls and cutaneous arteritis was diagnosed. Cyclophosphamide pulse therapy with steroid and anti-coagulation improved the neurological symptoms. A skin biopsy should be considered when patients present with mononeuritis multiplex in the lower extremities and cutaneous findings such as livedo reticularis in the symptomatic area.