A 12-year-old, spayed female Pekingese dog was presented with frequent syncope and exercise intolerance. Thoracic auscultation revealed a grade 4 heart murmur bilaterally and respiratory sinus arrhythmia. Electrocardiography indicated right axis deviation, suggesting right ventricular hypertrophy. Thoracic radiographs showed normal vertebral heart score of 9, vertebral left atrial size of 2.1, and intercostal space of 3.2, with an increased contact area between the sternum and right heart. Echocardiography revealed moderate tricuspid regurgitation and severe pulmonary hypertension (velocity 4.48 m/s; pressure gradient 80.4 mmHg). Based on diagnostic findings, congenital shunts, left-sided heart disease, tracheobronchial disease, pulmonary embolism, and heartworm disease were excluded, leading to a diagnosis of right-sided heart failure secondary to brachycephalic obstructive airway syndrome, with the characteristic narrow nostrils observed in the pekingese breed. The initial treatment with sildenafil citrate, along with pimobendan, enalapril maleate, and furosemide for right-sided heart failure, failed to improve syncope or pulmonary hypertension after three months. Beraprost sodium, a prostacyclin analog, was added, resulting in significant improvement in syncope despite unchanged echocardiographic findings (velocity 4.42 m/s; pressure gradient 78.2 mmHg). Clinical improvements persisted for 12 months with a regimen of sildenafil citrate (3 mg/kg PO bid) and beraprost sodium (20 µg/kg PO bid).

A 10-year-old spayed female Toy Poodle dog presented with nasal edema, erythema, pain, pruritus, and discharge. The size of the lesion had gradually increased, measuring 29 × 22.8 × 17.8 mm at the first visit. No infection was detected on microscopic cytologic evaluation of the nasal discharge. On radiography and computed tomography (CT), the nasal septum structure was normal, and bony invasion was not identified. On rhinoscopy, the soft tissues were thickened and erythematous. Decreased lumen diameter and severe congestion were found in the right nasal cavity. On histopathological examination of the right dorsal nasal skin lesion, there was multifocal-to-coalescing moderate-to-severe inflammation and fibrosis in the deep dermis and skeletal muscle layer. The inflammatory cells were primarily lymphocytes and plasma cells. Based on the patient history and test results, the patient was diagnosed with canine dermatomyositis. Treatment included immunosuppressive agents (prednisolone and cyclosporine) and antibiotics (amoxicillin/clavulanate). This treatment reduced the nasal edema, erythema, and lesion size. The diameter of the edematous area decreased by approximately 40%, with an 80% reduction in nasal discharge, and the dog demonstrated clinical benefits at a follow-up visit at 17 weeks. Although canine dermatomyositis usually develops before six months of age, this report demonstrates that this disease can also occur in adult dogs. Additionally, this is the first reported case of a dermatomyositis-like disease in a small breed dog which was histologically diagnosed and further characterized using immunohistochemistry, including VEGF and T-cell markers such as CD4 and CD8. The patient showed a favorable response to immunosuppressive therapy.