Ulnar Nerve Palsy as the Initial Presentation of Small Vessel Vasculitis With a Negative Antineutrophil Cytoplasmic Antibody Level

Abstract

Small-vessel vasculitis is a rare disease entity that affects the arteries, arterioles, capillaries, and venules of the circulatory system. Small vessel vasculitis can cause severe small vessel inflammation and multisystem involvement. The respiratory tract and kidneys are the most commonly affected organs, and occasionally neurological manifestations can occur. But neurological manifestation as the initial presentation without other system involvement is very rare. We report a case of a 16-year-old previously well female patient presenting with right lower limb distal muscle weakness associated with malaise, lethargy, and multiple joint pains for 2 weeks. On examination, she had palpable purpura below the knees with right sided ulnar nerve palsy. Her antineutrophil cytoplasmic antibody and antinuclear antibody testing was negative. A skin biopsy showed vasculitis involving small vessels. She was started on Prednisolone 60mg daily, followed by Mycophenolate Mofetil 500mg twice daily, and physiotherapy. She had a good clinical response to treatment over time.