INTRODUCTION: Congenital unilateral absence of a pulmonary artery (UAPA) is a rare abnormality, commonly accompanied by cardiovascular anomalies. It may occasionally occur as an isolated finding. UAPA on the right side is reported more commonly than the left side. Usually detected in childhood, most common presenting symptoms are recurrent pulmonary infections, dyspnea or exercise limitation, chest pain, pleural effusion, and hemoptysis. Some patients may be asymptomatic and the diagnosis may be missed or delayed. We report a case with UAPA diagnosed in a 43 year-old female.
CASE PRESENTATION: A 43-year-old Jamaican woman with a presumed diagnosis of asthma since childhood, recurrent episodes of chest infection, especially in winter months, presented with worsening dyspnea on exertion of three months duration. She had experienced similar symptoms three years ago. The patient is a nonsmoker and has two children. The rest of the medical history was non-contributory. Due to persistent symptoms, the patient was sent to emergency department for evaluation. The physical examination demonstrated an obese patient in mild respiratory distress, with normal vital signs. Her SaO2 at rest on room air was 95%. Auscultation of the respiratory system revealed mildly decreased breath sounds on the right side. Routine laboratory values including B-type natriuretic peptide and D-dimer were normal. The alveolar arterial O2 gradient (A-a gradient) was normal. Chest X-ray demonstrated mild cardiomegaly, reduced lung volume on the right side with mediastinal shift. The ventilation perfusion scan showed complete absence of perfusion to the entire right lung. Anticoagulation therapy was commenced and contrast-enhanced CT of the chest was performed. The latter was negative for pulmonary embolism (PE), but showed unilateral absence of right pulmonary artery with hypoplasia of right lung.
DISCUSSIONS: Our patient was diagnosed with asthma since childhood although she demonstrated little improvement with inhaled bronchodilators. She also suffered from recurrent chest infections all her life which were labeled as “recurrent bronchitis”. During her last hospitalization, she was started on anticoagulation based on the interpretation of the ventilation perfusion scan (V/Q mismatch). The diagnosis of PE was not corroborated by other laboratory data including A-a gradient and D-dimers. This confusing imaging and laboratory data, in the light of a relatively stable patient lead to the performance of chest CT. UAPA is a very rare congenital anomaly. Most often, it is diagnosed in childhood and young adults. The presenting symptoms are non-specific. Both these factors may result in a missed or delayed diagnosis in adults. Often, the absence of unilateral pulmonary artery in adults is missed on CT scans primarily because of the rarity with which it is encountered in this patient population.
CONCLUSION: Although UAPA is rare disease, this diagnosis should be considered by the clinician while evaluating patients with recurrent respiratory infections, dyspnea or exercise limitations. Radiologists should suspect this entity when a chest radiograph shows small hemithorax, especially when the V/Q scan shows unilateral complete absence of perfusion and relatively preserved ventilation in an otherwise stable patient. Confirming the diagnosis may be achieved with CT chest, MRI, echocardiogram or with the more invasive pulmonary angiogram.
DISCLOSURE: Ayman Bishay, None.