Osteoporosis Associated With Pulmonary Silicosis in an Equine Bone Fragility Syndrome

California horses incur a bone fragility syndrome manifested by pathologic fractures. This study investigated gross, radiographic, and histologic features of the disorder as well as relationships with silicosis and levels of heavy metals and trace minerals through a postmortem study of 9 affected an...

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Bibliographic Details
Published in:	Veterinary pathology Vol. 48; no. 3; pp. 593 - 615
Main Authors:	Arens, A. M., Barr, B., Puchalski, S. M., Poppenga, R., Kulin, R. M., Anderson, J., Stover, S. M.
Format:	Journal Article
Language:	English
Published:	Los Angeles, CA SAGE Publications 01-05-2011
Subjects:	Animals Bone and Bones - pathology Bone Diseases, Metabolic - complications Bone Diseases, Metabolic - epidemiology Bone Diseases, Metabolic - pathology Bone Diseases, Metabolic - veterinary California - epidemiology Female Horse Diseases - epidemiology Horse Diseases - etiology Horse Diseases - pathology Horses Lung - chemistry Lung - pathology Lymph Nodes - pathology Male Osteoporosis - epidemiology Osteoporosis - etiology Osteoporosis - pathology Osteoporosis - veterinary Silicon - chemistry Silicosis - epidemiology Silicosis - etiology Silicosis - pathology Silicosis - veterinary California pulmonary silicosis metabolic bone disease cristobalite osteoporosis granulomatous pneumonia equine granulomatous lymphadenitis
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Summary:	California horses incur a bone fragility syndrome manifested by pathologic fractures. This study investigated gross, radiographic, and histologic features of the disorder as well as relationships with silicosis and levels of heavy metals and trace minerals through a postmortem study of 9 affected and 3 unaffected horses. Bones and soft tissues were evaluated grossly and histologically. Bones, lymph nodes, and lung tissue were evaluated radiographically. Tissues were evaluated for silicon levels, intracytoplasmic crystals, heavy metals, and trace minerals. All 9 affected horses had osteoporosis and clinical or subclinical pulmonary disease due to silicosis (8/9) or pneumoconiosis (1/9). All affected horses had radiographic findings consistent with osteopenia and histologic evidence of osteoporosis characterized by osteopenia, numerous resorption cavities, cement lines, and a mosaic lamellar pattern indicative of multiple remodeling events. Silicosis was characterized by widespread pulmonary granuloma formation with fibrosis; variable tracheobronchiolar and mediastinal granulomatous lymphadenitis; intracellular crystals within lung and lymph node macrophages; and pronounced lymph node fibrosis, focal necrosis, and dystrophic calcification. Crystals in lung (6/9) and lymph node (8/9) tissues were identified as cytotoxic silica dioxide polymorphs. Lung and liver tissue from affected horses had elevated levels of elemental silicon. Osteoporosis was highly correlated (r = 0.8, P < .01) with silicosis. No abnormalities in heavy metal or trace minerals were detected. This evaluation indicated that horses with bone fragility disorder have systemic osteoporosis associated with fibrosing pulmonary silicosis. The etiopathogenesis of the bone fragility syndrome is unknown; however, this study provides circumstantial evidence for a silicate associated osteoporosis.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0300-9858 1544-2217
DOI:	10.1177/0300985810385151