Cutaneous manifestations and histological features of microscopic polyangiitis.

Purpura and livedo are common cutaneous manifestations of microscopic polyangiitis (MPA); however, only a few clinical analyses focusing on the relationship between clinical symptoms and the affected vessels in the skin have been reported. We herein report the cutaneous manifestations and histological features of four patients with MPA. In two patients, a Henoch-Shönlein purpura-like eruption developed with necrotizing vasculitis localized in the upper dermis. The other two patients presented with livedo racemosa; with histological findings of necrotizing vasculitis of the small vessels around the muscle fibers or from the deep dermis to subcutaneous tissue. Two patients' cases were complicated by systemic sclerosis and had poor prognoses. MPA can present with various cutaneous manifestations. Additional research is required to ascertain the relationship between the prognosis and the affected vessels.