A 4-year-old female inland bearded dragon ( Pogona vitticeps ) with a history of tenesmus was found dead one month after surgical debulking of a palpable caudal coelomic mass. At necropsy, a 2.5 cm diameter, firm, lobulated, tan-yellow mass was associated with the wall of the pelvic canal and bilateral masses were present in the caudal pharynx (0.6 cm and 3.0 cm in diameter), the largest of which was soft and dark red. Histologically, the mass within the pelvic canal arose from the coelomic wall and consisted primarily of fibrocollagen with myxoid to cystic regions, and mixed inflammatory infiltrates. Additional findings included granulomatous dermatitis, myositis/cellulitis, coelomitis, encephalitis, and pneumonia. Vasculitis was detected in multiple organs and, in the pharynx, resulted in aneurysmal dilation and perivascular hemorrhage leading to mass-like lesions. Within all lesions, scattered macrophages contained oval, weakly basophilic, Gram-positive, slightly refractile, 1–2 μm diameter ovoid organisms consistent with microsporidia. A diagnosis of systemic microsporidiosis characterized by lymphohistiocytic and heterophilic vasculitis with medial hypertrophy and fibrinoid necrosis was made. Using DNA sequencing, the organism was identified as Encephalitozoon pogonae . Encephalitozoon pogonae should be considered a differential diagnosis for vasculitis and aneurysms in bearded dragons.

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