Pneumonia piogranulomatosa fúngica em canino

Resumo

Background: Pulmonary consolidation is the collapse of one or more lobes, which may occur due to worsening pneumonia, with the suggestive radiographic sign being an increase in radiopacity of soft tissues in the lung lobes. Zygomycosis is an infection caused by fungi that can lead to chronic focal infections in the subcutaneous tissue or nasal submucosa and acute and progressive diseases in immunocompromised patients. This report aimed to describe the clinical-laboratory, radiographic, ultrasonographic and histopathological findings of a dog treated at a university veterinary hospital in Cuiabá, with diffuse pyogranulomatous pneumonia associated with zygomycete fungi.

Case: A male dog, no defined breed, approximately ten years old, was attended in emergency at the Veterinary Hospital of the Federal University of Mato Grosso, Cuiabá campus, with complaint of hyporexia and progressive weight loss for two weeks, three episodes of emesis in the previous week, and severe coughing after eating or drinking water. The patient had a body condition score of one, tachypnea, crackles on pulmonary auscultation, presence of nasal secretion, and depressed general condition, with a reserved prognosis. In view of the condition, additional tests were performed. The thoracic radiograph showed increased radiopacity of soft tissues in lung fields, characterized by a mixed alveolar and bronchial pattern; and the lung ultrasound evaluation showed a flap sign and consolidation/hepatization of the lung lobes of the right hemithorax. During hospitalization, the patient was presented with worsening dyspnea with constant need for oxygen support. Given the critical clinical condition, it was decided to perform euthanasia and necropsy. At necropsy, involving the carina region and extending to the bronchi, an irregularly thickened wall was noted, surrounded by firm, irregular, yellowish and misshapen content that continued with the surrounding lung parenchyma. The right lung presented a firm, yellowish-white surface, extending to the cranial, middle, accessory and caudal lobes. Microscopic analysis revealed replacement of the lung parenchyma by inflammatory infiltrate (composed of mononuclear, epithelioid and multinucleated cells, a smaller number of neutrophils and lymphocytes), with areas of amorphous hyaline material with basophilic mixtures (caseous necrosis) containing in their center images structures similar to hyphae, with strong staining by Grocott's silver methenamine technique, with aspects similar to hyphae of zygomycete fungi. In the tissue adjacent to the inflammatory reaction, an inflammatory infiltrate composed of plasma cells, lymphocytes, eosinophils, neutrophils and giant cells was observed.

Discussion: It was concluded that the patient had diffuse, severe, chronic pyogranulomatous fungal pneumonia, associated with zygomycete fungi. Pneumonia can be an important cause of coughing in dogs, and in more advanced stages, it can lead to consolidation of one or more lung lobes, as in this case. In more advanced cases, on thoracic ultrasound, the lung presents echogenicity and echotexture similar to the liver, characterizing hepatization of the lung parenchyma, which also happened in this case. The radiographic pattern of fungal pneumonias is usually unstructured interstitial and can be diffuse or nodular (with a miliary appearance). However, this dog presented a consolidation pattern, which is not common for pulmonary fungal infections; it can be concluded that this dog presented an unusual form of the disease, and its condition is probably related to immunosuppression. This report reinforced the severity of the disease, especially in immunosuppressed animals or those that received a late diagnosis, and also the importance of performing laboratory and imaging tests, seeking to reach an earlier and assertive diagnosis.