Osteoporosis associated with pulmonary silicosis in an equine bone fragility syndrome.
Authors: Arens A M, Barr B, Puchalski S M, Poppenga R, Kulin R M, Anderson J, Stover S M
Journal: Veterinary pathology
Summary
# Editorial Summary: Silica Exposure and Equine Bone Fragility A cohort of California horses presenting with pathologic fractures underwent comprehensive postmortem investigation to characterise the underlying bone pathology and identify potential aetiological factors. Gross, radiographic, and histological examination of bone tissue from nine affected and three control horses was combined with elemental analysis of multiple tissues and investigation of pulmonary disease. All affected horses demonstrated systemic osteoporosis with characteristic resorption cavities and remodelling patterns, and eight of nine showed concurrent silicosis characterised by pulmonary granulomas, fibrosis, and intracellular silica dioxide crystals within lung and lymph node macrophages; significantly, osteoporosis correlated strongly with silica burden (r = 0.8, *P* < 0.01). Elevated elemental silicon concentrations were detected in lung and liver tissue from affected animals, whilst heavy metal and trace mineral imbalances were not implicated. Although the precise mechanisms remain unclear, this work provides compelling evidence linking occupational or environmental silica exposure to a systemic osteoporotic state in horses. For practitioners, these findings underscore the importance of respiratory health assessment in cases of stress fractures or poor fracture healing, and suggest that dust management strategies addressing fine silica particles may warrant consideration alongside nutritional and biomechanical interventions in at-risk populations.
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Practical Takeaways
- •Horses presenting with pathologic fractures or recurrent bone injuries should be evaluated for pulmonary disease; silicosis may indicate systemic osteoporosis risk.
- •Environmental silica exposure (dust, footing, water sources) warrants investigation in herds with unexplained fracture cases or bone fragility problems.
- •Standard mineral supplementation may be ineffective for this syndrome; identifying and eliminating silicate exposure sources should be the management priority.
Key Findings
- •All 9 affected horses demonstrated systemic osteoporosis with histologic evidence of osteopenia, resorption cavities, and multiple bone remodeling events.
- •Osteoporosis was highly correlated with silicosis (r = 0.8, P < 0.01), with 8/9 affected horses having clinical or subclinical pulmonary silicosis.
- •Silicon dioxide crystals were identified in lung (6/9) and lymph node (8/9) tissues from affected horses, with elevated elemental silicon in lung and liver tissue.
- •No abnormalities in heavy metals or trace minerals were detected, suggesting silicate exposure as a primary risk factor rather than nutritional deficiency.