Leukocytoclastic Vasculitis Presenting With Peripheral Neuropathy and Foot Drop in an Adolescent: A Case Report.

Leukocytoclastic vasculitis (LCV) is a small-vessel vasculitis that typically presents with palpable purpura on the lower extremities and is often confined to the skin. Peripheral nerve involvement is uncommon. We describe the case of a 17-year-old female who developed progressive burning paresthesias in all four limbs, asymmetric sensory loss, autonomic symptoms, and left foot drop preceding the appearance of palpable purpura and necrotic lesions on both lower limbs. Nerve conduction studies demonstrated mixed demyelinating and axonal motor neuropathy in both lower limbs, more pronounced on the left, with additional motor axonal involvement of the right median nerve. Sympathetic skin responses were absent in all four limbs. An extensive evaluation for infectious, connective-tissue disease-related, antineutrophil cytoplasmic antibody-associated, and paraproteinemic causes was unrevealing. Skin punch biopsy demonstrated dermal perivascular inflammation, leukocytoclasis, erythrocyte extravasation, and fibrinoid necrosis of small-vessel walls; direct immunofluorescence was positive for complement component 3 (C3), immunoglobulin M (IgM), and IgA. These findings were consistent with LCV. The patient was treated with intravenous methylprednisolone followed by oral corticosteroids and hydroxychloroquine, along with two doses of rituximab. The patient demonstrated marked improvement in left ankle dorsiflexion, with Medical Research Council (MRC) muscle power improving from 2/5 to 4+/5, and was able to walk independently without assistance. No new skin lesions developed. This report highlights that neurologic manifestations may precede the characteristic cutaneous eruption of LCV and that early electrophysiologic assessment and tissue biopsy can facilitate prompt diagnosis and treatment.