Figure 1:

Histopathology of Pulmonary Lesions in TA-TMA

A. Classic features of TMA are present. Acute endothelial injury is associated with subendothelial intimal myxoid widening. Red cell fragments are present in the thickened intimal space (indicated with dashed line) and the lumen is narrowed (thin arrow). The parenchyma of the lung demonstrates diffuse alveolar damage and hemorrhage (indicated in a thick arrow).

B. A small vessel near the hilum has a markedly thickened wall with intimal fibrosis and a narrowed lumen.

C. Similar to A, there is marked subendothelial myxoid widening with near occlusion of the lumen.

D. This case had vascular changes and endothelial injury with an unusual finding of intimal arteritis. There is a prominent perivascular lymphocytic infiltrate around the vessel. The intima is thickened and there are lymphocytes along the intimal surface. The lumen is markedly narrowed.

E. This systemic pleural vessel has a narrowed lumen associated with a hyalinized and thickened wall. Intimal thickening with slight myxoid change and few red cell fragments are also present.