Idiopathic systemic granulomatous disease and macrophage expression of PTHrP in a miniature pony

Idiopathic systemic granulomatous disease, which has been reported in horse s, cattle and human beings, is characterized by perivascular granulomatous and lymphoplasmacytic inflammation in many organ systems. Diagnosis is base d on the exclusion of possible viral, fungal or bacterial causes. The disea se was identified in a miniature pony with widespread lymphoplasmacytic and granulomatous inflammation, special staining techniques having revealed no evidence of any aetiological agent. Skin lesions, which were severe, consi sted of hyperkeratosis and serocellular crust formation, with inflammatory infiltrates in a perivascular to diffuse pattern in both the superficial an d deep dermis. Inflammatory infiltrates were also present in lymph nodes an d around the blood vessels in most organs. Immunohistochemically, both CD3- positive T lymphocytes and BLA36-positive B lymphocytes were identified in the inflammatory infiltrates, and macrophages were immunolabelled for parat hyroid hormone-related protein, a factor associated with hypercalcaemia in human beings with granulomatous diseases. (C) 2001 Harcourt Publishers Ltd.