HO in horse also occurs in maxilla and mandible....

Generalized sarcoidosis associated with hypertrophic osteopathy in a Standardbred racehorse.

A Charles, H. Vande Kerckhove, L. De Maré, et al.

Background
Equine sarcoidosis (ES) is a rare, poorly understood disorder characterized by granulomatous inflammation affecting various tissues. Its systemic manifestation, idiopathic systemic granulomatous disease (ISGD), is associated with wasting symptoms and chronic inflammation. Hypertrophic osteopathy (HO) is a rare paraneoplastic or inflammatory condition, characterized by periosteal bone proliferation and often linked to intrathoracic or extrathoracic pathology. This study reports a unique case of ISGD and HO in a Standardbred racehorse.

Methods
A 6-year-old Standardbred gelding with exercise intolerance, pyrexia, weight loss, and facial deformity underwent extensive diagnostic evaluations, including hematology, imaging (radiography, ultrasonography, computed tomography), endoscopy, and histopathology. Polymerase chain reaction (PCR) was used to detect microbial DNA. Diagnostic tools also included fine-needle aspiration and skin biopsies.

Results
-Clinical Findings: Bilateral periosteal new bone formation in the limbs and periostitis in the maxillary bone were observed. Skin lesions indicated granulomatous dermatitis.

-Imaging: Radiographs showed bilateral periosteal new bone proliferation, consistent with HO. Computed tomography excluded dental or sinus infections.

-Histopathology: Revealed granulomatous inflammation in various tissues, including the skin and lungs, confirming ISGD.

-Microbial Testing: PCR detected equine herpesvirus 5 (EHV-5) DNA, potentially implicating it in granulomatous lesions.

The horse's condition deteriorated rapidly, leading to euthanasia. Post-mortem analysis confirmed systemic granulomatous lesions and HO.

Limitations
The study was limited by the inability to establish a definitive causal relationship between EHV-5 and ISGD. The owner declined corticosteroid treatment, precluding evaluation of its efficacy in this case.

Conclusions
This case highlights the rare comorbidity of ISGD and HO in a horse, with possible involvement of EHV-5. The findings suggest diagnostic importance for imaging and histopathology in similar cases. Further research is needed to elucidate the etiology and pathophysiology of these conditions in horses.

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