Pneumocystis carinii infection with severe pneumomediastinum and lymph node involvement in a Whippet mixed-breed dog.

A 3.5-y-old Whippet mixed-breed dog was presented with a history of respiratory distress, exercise intolerance, and generalized demodicosis. Hematologic alterations included marked leukocytosis and neutrophilia. Radiographic examination showed a diffuse interstitial and mild peripheral alveolar lung pattern and pneumomediastinum. Because the cytologic examination of the bronchoalveolar aspirate was not diagnostic and a persistent perforation of the upper respiratory tract could not be ruled out, the dog was submitted to thoracoscopy, and subsequently the left cranial lung lobe as well as mediastinal and sternal lymph nodes were resected. Pulmonary pneumocystosis with spread to the thoracic lymph nodes was suspected after histologic investigation of lung and lymph nodes, which was confirmed by in situ hybridization, PCR, and subsequent Sanger sequencing. We document a rare, simultaneous occurrence of severe pulmonary and thoracic lymph node pneumocystosis with spontaneous pneumomediastinum in a dog. Definitive diagnosis was achieved through the use of Grocott methenamine silver staining, in situ hybridization, and PCR.

Relaxin of prostatic origin might be linked to perineal hernia formation in dogs.

Perineal hernia occurs spontaneously in older male dogs after idiopathic weakening of the pelvic diaphragm. Hernias invariably contain cystic paraprostatic tissues. Castration reduces incidence and recurrence after surgical repair. Although cystic prostatic hypertrophy is a consistent feature in patients with perineal hernia, an endocrine link of the disease to steroid sex hormones has not been demonstrated. Employing immunohistochemistry, we found intense relaxin immunoreactivity in dogs with perineal hernia within the epithelia of hypertrophic prostates and in periprostatic tissues. The prostate of normal dogs exhibited similar but less intense relaxin staining. In neutered dogs with prostatic atrophy, relaxin immunostaining was weak or absent. Periprostatic cysts highly expressed relaxin precursors in the fluid phase as shown by SDS-gel electrophoresis. Relaxin of prostatic origin, therefore, is possibly a local factor in connective tissue weakening and subsequently in perineal hernia formation.