Multifocal discrete osteolysis in a horse with silicate associated osteoporosis.
Authors: Zavodovskaya R, Eckert M, Murphy B G, Stover S M, Kol A, Diab S
Journal: Equine veterinary education
Summary
# Editorial Summary: Silicate-Associated Osteoporosis Presenting as Multifocal Osteolysis A 2-year exposure to cytotoxic silicates proved sufficient to trigger silicate-associated osteoporosis (SAO) in an adult horse, making this the shortest documented timeframe for disease development and highlighting a clinically important diagnostic consideration. The case involved an equine presenting with progressive back tenderness, severe forelimb lameness (4/5), moderate hindlimb ataxia and cervical pain; radiographs revealed sharply demarcated osteolytic lesions throughout the skull, vertebral column, ribs, scapulae and P2 of the affected forelimb alongside bronchointerstitial lung changes—findings that initially suggested metastatic neoplasia. Post-mortem examination confirmed pulmonary silicosis and characteristic histological features of SAO, including excessive osteoclastic activity and disrupted bone remodelling, which differentiated the condition from malignant disease. For practitioners managing horses with a history of endemic silicate exposure, SAO warrants inclusion in differential diagnoses for multifocal discrete osteolysis, particularly when radiographic lesions appear sharply delineated and widespread across multiple skeletal sites without obvious primary neoplastic disease. Early recognition of exposure risk and vigilance for progressive musculoskeletal and respiratory signs may enable earlier intervention, though prognosis appears grave once osteolytic lesions are established.
Read the full abstract on PubMed
Practical Takeaways
- •Consider silicate-associated osteoporosis in the differential diagnosis for horses presenting with progressive back pain, lameness, and ataxia, particularly those with exposure to endemic silicate-rich regions
- •Two years of silicate exposure may be sufficient to develop clinically significant bone disease; assess grazing and work environment history for potential silicate inhalation sources
- •Widespread discrete osteolytic lesions on radiographs are not pathognomonic for neoplasia—environmental toxin exposure should be evaluated before pursuing aggressive diagnostic workup
Key Findings
- •SAO was diagnosed post mortem in an adult horse with only 2 years of documented cytotoxic silicate exposure, representing the shortest known exposure period to develop this condition
- •Radiographic findings showed widespread discrete osteolytic lesions in skull, vertebral column, ribs, scapulae, and P2, mimicking metastatic osteolytic neoplasia
- •Post mortem histology revealed numerous large osteoclasts and disorganized bone remodeling consistent with SAO pathophysiology
- •SAO should be included in the differential diagnosis for horses with multifocal osteolysis and endemic silicate exposure history