Histologic findings: Alveolar wall necrosis (A), probably ischemic in origin, is a characteristic lesion in these patients. At the arrows, the wall is inflamed. PMNs are present in the wall and in the surrounding alveolar spaces. A few macrophages are near the center top.

A

At higher magnification, a fibrinous exudate is present around the necrotic alveolar wall. Despite the presence of inflammation, alveolar hemorrhage is scant. The non-necrotic walls have capillaries that are distended by sickle RBCs.

B

Clinical summary Image 4

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