Refractory anemia as a presenting feature of microscopic polyangiitis: a rare vasculitis in children.

Microcytic anemia refractory to usual supplementation is an important clue to an alternative diagnosis. Accompanying pulmonary and renal involvement during the disease course suggests a multisystem disease. Small-vessel vasculitis should be suspected in any patient who presents with a multisystem disease that is not caused by an infectious or malignant process. Among these, antineutrophilic cytoplasmic antibodies (ANCA)-associated vasculitis is a distinct subclass involving anti-neutrophil cytoplasmic antibody (ANCA) as the common pathogenesis. Microscopic polyangiitis is a rare form of such vasculitis in children characterized by pulmonary-renal syndrome with pauci-imune rapidly progressive glomerulonephritis and a poor outcome.