Vascular lesions in nine Göttingen minipigs with thrombocytopenic purpura syndrome.

Tissues from 9 Göttingen minipigs, aged 7 weeks to 1 year, with clinically diagnosed thrombocytopenic purpura syndrome were examined microscopically. All pigs had a history of spontaneous cutaneous purpura that was generally accompanied by disseminated visceral hemorrhages. Hematologic abnormalities included anemia (8 out of 9 pigs) and thrombocytopenia (7 out of 9 pigs), with platelet counts consistently below 20,000/microl. Microscopically, degenerative vascular lesions with morphologic features of arteriosclerosis were present in all 9 pigs. Vascular lesions affected small- to medium-sized muscular arteries and arterioles in various organs and extraparenchymal tissues; vessels of the renal pelvis and coronary arteries were consistently involved. Microscopic lesions in small- to medium-sized muscular arteries consisted of neointimal proliferation, medial thickening, luminal stenosis, thrombosis, disruption and fragmentation of the internal elastic lamina, necrosis of the tunica media, and medial deposits of myxoid matrix material. Microscopic lesions in arterioles included concentric laminar thickening of vessel walls (onion-skin pattern), endothelial cell hypertrophy, smooth muscle cell vacuolation, necrosis of the tunica media, thrombosis, and partial to complete luminal stenosis. Arteritis and/or periarteritis were also noted in 4 out of 9 pigs. Additional microscopic lesions included membranoproliferative glomerulonephritis (3 out of 9), myocardial microinfarcts (4 out of 7), renal interstitial fibrosis (2 out of 9), extramedullary hematopoiesis (6 out of 9), and intracapillary hyaline thrombi (2 out of 9). Degenerative vascular lesions have not been previously described in Göttingen minipigs with thrombocytopenic purpura syndrome. The etiopathogenesis of both the vascular lesions and thrombocytopenic purpura syndrome is currently unknown.