September 2017



SIGNALMENT (JPC# 4069782): 3-month-old miniature horse filly

HISTORY: This filly presented with a one week history of non-resolving respiratory congestion.  High fever and increased respiratory rate were noted and (unspecified) treatment was initiated.  The patient was initially responsive to care, but subsequently had two seizures and died

HISTOPATHOLOGIC DESCRIPTION: Effacing approximately 40% of the normal pulmonary parenchyma there are multiple pyogranulomas (up to 11mm) composed of a central core of necrosis with numerous degenerate neutrophils and macrophages, admixed with necrotic cellular debris, fibrin and scattered mineral, surrounded by epithelioid macrophages, fewer multinucleated giant cells, and low numbers of lymphocytes and plasma cells.  Macrophages and multinucleated giant cells are often packed with numerous 1-2um basophilic coccobacilli. Similar inflammatory cells (including macrophages packed with coccobacilli), necrotic debris and fibrin fill remaining bronchioles, infiltrating through the bronchiolar epithelium/wall to fill adjacent alveoli and efface alveolar septa (necrosis). There is multifocal type II pneumocyte hyperplasia.  Bronchiolar epithelial cells are multifocally necrotic with sloughing into the lumen. In less affected areas, alveolar septa are expanded up to 4 times normal by fibrin, edema and low numbers of macrophages.  There are multifocal areas of mild hemorrhage and a few hemosiderin-laden macrophages are present.  The pleura and interlobular septa are expanded up to 5 times normal by fibrin and edema.  Multifocally, vascular walls contain mild neutrophilic infiltrate and are rimmed by moderate perivascular edema.

MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, pyogranulomatous and necrotizing, multifocal-to-coalescing, chronic-active, severe, with numerous intrahistiocytic coccobacilli, miniature horse, equine.

ETIOLOGIC DIAGNOSIS:  Rhodococcal pneumonia

CAUSERhodococcus equi








Granulomatous pneumonia

Foal pneumonia:





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