Feline Idiopathic Pulmonary Fibrosis

Abstract

Background: Feline idiopathic pulmonary fibrosis is an irreversible disease that is rarely reported in veterinary clinical routine, with this case as the second reported in Brazil. This study aimed to describe a case of idiopathic pulmonary fibrosis in a domestic cat.

Case: A 10-year-old female cat with a history of respiratory distress was treated at the Veterinary Hospital of the State University of Santa Cruz (HV-UESC). The first signs were observed three months before clinical care, characterized mainly by dyspnea that was more pronounced during nighttime. There was no history of previous illnesses or prior drug use. The cat lived with two other domiciled cats, did not have access to the street, and had restricted access to the terrace of the building, from where other animals could have possibly entered. Physical examination showed a poor body condition with a temperature of 37°C and dehydration estimated at 9%.The animal was observed to remain in an orthopedic position, with tachypnea (109 mvm), wheezing through the mouth, and severe expiratory dyspnea. Pulmonary auscultation detected fine discontinuous adventitious noises. There were no changes in the cardiac function in terms of rhythm, frequency, or auscultation. Oxygen therapy and slow administration of 0.9% NaCl solution were performed; moreover, blood was collected for complete blood count, in which no abnormalities were observed. Thoracic radiography was performed on the cat, and the results showed a mixed pulmonary pattern characterized by bronchiectasis, thickening of the bronchiolar wall, and an unstructured interstitial pattern throughout the pulmonary area. Shortly after the beginning of the clinical care, the animal died due to respiratory arrest and was necropsied. The main macroscopic finding was pulmonary edema. Lung samples were subjected to microscopic evaluation, which revealed extensive multifocal areas of alveolar septa thickening characterized by smooth muscle hyperplasia, hypertrophy associated with intense fibroplasia, type II pneumocyte hyperplasia, and discrete intra-alveolar and interstitial lymphohistiocytic inflammatory infiltrate. Based on the clinical, radiographic, macroscopic, and histopathological findings, the diagnosis of idiopathic pulmonary fibrosis was established.

Discussion: This is the second case of feline idiopathic pulmonary fibrosis reported in Brazil. The observations in the physical examination, namely, the orthopedic positioning, dyspnea, and mouth breathing, are characteristic of respiratory distress and showed the severity of the lesions in the respiratory system. The clinical manifestation of idiopathic pulmonary fibrosis in cats reveals that gas exchange had already been compromised, which indicates an advanced stage of disease. In addition to respiratory signs, systemic signs such as apathy, anorexia, weight loss, and dehydration also confirm the severity of the condition. Because of the severity of the clinical condition at the time of the clinical care, it was not possible to adopt a more aggressive therapeutic approach, and the animal eventually died. Taken together, the clinical, radiographic, macroscopic, and histopathological findings led to the diagnosis of idiopathic pulmonary fibrosis. Literature states that the diagnosis of idiopathic pulmonary fibrosis requires clinical, radiographic, and histopathological findings consistent with the alterations observed in this cat. Much remains to be understood with regard to idiopathic pulmonary fibrosis in felines, since the currently available information is sparse and divergent. The description of these cases is extremely important to increase the available knowledge and to improve the prognosis and therapy for this serious disease.