Presentation
Presented with a 6-month history of waxing and waning tachypnea, respiratory difficulty, and diffuse pulmonary infiltrates.
Patient Data
The lung is diffusely affected with multiple patchy ill-defined areas of increased opacity. On the radiographs, these seem to be centered around airways. The heart and vessels appear normal.
All lung lobes are affected with multi-focal to diffuse, ill-defined, soft tissue dense infiltrates containing focal mineralization. The right cranial and middle lung lobes are affected slightly more than the remaining lung lobes. The infiltrates are associated primarily with airways which otherwise are of normal size and taper appropriately. Many of the lesions are peripherally located and extend to the pleural surface. The lungs are hyperinflated. Moderate tracheobronchial lymphadenopathy is identified.
Sections of the lung lobes illustrate the pulmonary nodules throughout the parenchyma.
Case Discussion
Differential diagnosis
Diffuse, airway associated pulmonary infiltrates consistent with severe, chronic inflammatory disease. Infectious causes such as fungal, parasitic or bacterial granulomatous disease as well as non-infectious inflammatory causes can be considered.
Diagnosis
HISTOPATHOLOGICAL SUMMARY:
(T1, T2) Lung: Examined are three similarly affected sections of lung in which nearly 100% of the examined pulmonary parenchyma is disrupted by a marked alveolar inflammatory cell infiltrate. Coalescing alveolar spaces are severely distended and contain numerous non-degenerate neutrophils and large foamy macrophages. The alveolar epithelium is multifocally lined by large plump reactive cuboidal to columnar epithelial cells (type II pneumocyte hyperplasia) which often are sloughed into the alveolar space. Abundant fibrous connective tissue and multifocal variably thick bundles of smooth muscle are present multifocally in alveolar septa. Abundant thick bands of fibrous connective tissue surrounds and bridges between bronchi. Bronchiolar lumina often contain abundant cellular debris similar to that identified in the alveoli (primarily neutrophils and histiocytes) admixed with a small to moderate amount of mucous. Increased numbers of mucous cells are present in the bronchiolar epithelium. Small scattered foci of mineralization are present throughout the lung. The visceral pleura is moderately thickened by dense connective tissue. Pulmonary interstitial lymphoid nodules (BALT) are minimally populated with lymphocytes.
COMMENT:
The underlying etiology for these severe pulmonary lesions is not determined. Warthin-Starry and B&B (tissue Gram) stains were employed to identify a bacterial agent but were negative. The diffuse nature of pulmonary lesions, young age of this cat, lack of viral inclusions and inability to identify an underlying infectious etiology may suggest a congenital defect in pulmonary function, but this remains unknown.
Discussion
An underlying cause of the severe inflammatory disease was not identified, likely due to the chronicity of the condition.
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