We present an adult patient with Henoch-Schönlein Purpura who developed mononeuropathy in the common peroneal nerve. Upon admission, the patient had palpable purpura in the arms and legs, polyarthralgia, abdominal pain, and leukocytoclastic vasculitis in the skin biopsy. These symptoms disappeared with 30 mg daily of oral prednisolone. One month later, after induction therapy, fever, livedo reticularis and peripheral mononeuropathy developed with hypocomplementemia and the patient was treated successfully with glucocorticoid pulse therapy.