MYELOFIBROSIS IN YOUNG PYGMY GOATS

Marked widespread myelofibrosis occurred in 11 of 16 pygmy goats from seven litters (two sires and four dams). Sires and darns were haematol ogically normal. Clinical histories of affected goats included letharg y, poor weight gain, and pale mucous membranes. Anaemia and neutropeni a resulted in death within 6-12 weeks of age. A diagnosis of myelofibr osis was confirmed histologically in nine goats and was based on clini cal signs and history in the remaining two littermates. The marrow of long bones was most severely affected with proliferation of well-diffe rentiated fibrocytes and abundant collagen deposition. There was bone marrow megakaryocyte hyperplasia, individual megakaryocyte necrosis, m egakaryocyte emperipolesis of haematopoietic cells, and clusters of de generative megakaryocytes were present adjacent to some fibrotic foci. Prominent areas of extramedullary haematopoiesis were present in many organs but were most consistently observed in liver, thymus gland, an d lymph nodes. The aetiopathogenesis of marrow fibrosis was not determ ined; however, clinical, haematological, and/or bone marrow morphologi cal features in the goats were similar to findings in anaemic dogs wit h congenital pyruvate kinase deficiency or in human beings with myelof ibrosis due to dysmegakaryocytopoiesis.