Cutaneous manifestations in patients with microscopic polyangiitis: two case reports and a minireview.

Microscopic polyangiitis is a systemic small vessel vasculitis, which often has cutaneous and musculoskeletal features. Microscopic polyangiitis is a member of the family of anti-neutrophil cytoplasmic auto-antibody (ANCA)-associated vasculitides and is strongly associated with anti-myeloperoxidase (MPO)-ANCA. Titres of MPO-ANCA may reflect disease activity and play a pathogenic role. Patients with microscopic polyangiitis usually present with erythematous macules on the extremities as the first cutaneous manifestation. Skin biopsy specimens from the erythema reveal small-sized vessels that are infiltrated with neutrophils, consistent with leukocytoclastic vasculitis, in the deep dermis to the subcutaneous fat tissue. The cutaneous involvement is present at an early stage of microscopic polyangiitis with other non-specific symptoms, such as arthralgias and myalgias. The initial cutaneous manifestations are important in early diagnosis of possible ANCA-associated vasculitides with elevated ANCA titres.