Genetics of Pulmonary Arterial Hypertension

Heritable pulmonary arterial hypertension complicated by multiple pulmonary arteriovenous malformations

Heritable pulmonary arterial hypertension (HPAH) is a type of familial pulmonary arterial hypertension, while pulmonary arteriovenous malformations (PAVMs) are abnormal communications between pulmonary arteries and veins that occur frequently in patients with hereditary hemorrhagic telangiectasia (HHT). A 21-year-old woman on continuing medication for HPAH was hospitalized. She had been diagnosed with HPAH at age 4 years and had been receiving epoprostenol infusion from age of 9 years. Although lung perfusion scintigraphy showed a shunt fraction of 18.9% at age of 19 years, the cause of the shunt was unclear. At the time of the present hospitalization, enhanced computed tomography (CT) of the chest and four-dimensional reconstructed images revealed multiple abnormal communications between the peripheral pulmonary arteries and veins. Furthermore, right heart catheterization revealed an elevated mean pulmonary arterial pressure. Wedged angiography of the pulmonary artery of the right lower lobe revealed several PAVMs. Multiple PAVMs and suspected HHT with HPAH was diagnosed. The possibility of PAVMs should be considered even in patients with HPAH. Moreover, evaluation of the shunt fraction by lung perfusion scintigraphy and morphological examination of PAVM by contrast-enhanced CT may facilitate PAVM detection in patients with HPAH.

Effect of treatment with epoprostenol and endothelin receptor antagonists on the development of thyrotoxicosis in patients with pulmonary arterial hypertension

Thyroid disease is known to be associated with pulmonary arterial hypertension (PAH). We investigated the prevalence of thyroid disease in patients with idiopathic PAH (IPAH) or heritable PAH (HPAH), and the factors affecting the pathogenesis of thyroid disease. We retrospectively evaluated 59 patients with IPAH or HPAH who had been diagnosed with PAH before the age of 20 years. Thyrotoxicosis was detected in 12 of the 59 patients (6 patients with Graves' disease, 3 with hashitoxicosis, and 3 with silent thyroiditis) after the start of PAH treatment. The proportion of patients who received epoprostenol in the thyrotoxicosis group was significantly higher than that in the euthyroid group (12/12 vs. 27/47, p=0.015). In the 39 patients treated with epoprostenol, the proportion of patients who received combination therapy with epoprostenol and an endothelin receptor antagonist (ERA) in the thyrotoxicosis group was significantly lower than that in the euthyroid group (5/12 vs. 23/27, p=0.016). Logistic regression analysis revealed that thyrotoxicosis development was significantly associated with administration of epoprostenol (odds ratio [OR] 8.22, 95% confidence interval [CI] 1.26-53.74, p=0.028) and non-administration of ERA (OR 5.33, 95% CI 1.29-22.06, p=0.021). The prevalence of thyrotoxicosis was high in patients with IPAH or HPAH. The onset of thyrotoxicosis might be promoted by epoprostenol and inhibited by ERA.

Animal Models of Pulmonary Hypertension: Matching Disease Mechanisms to Etiology of the Human Disease

Recently a great deal of progress has been made in our understanding of pulmonary hypertension (PH). Research from the past 30 years has resulted in newer treatments that provide symptomatic improvements and delayed disease progression. Unfortunately, the cure for patients with this lethal syndrome remains stubbornly elusive. With the relative explosion of scientific literature regarding PH, confusion has arisen regarding animal models of the disease and their correlation to the human condition. This short review uniquely focuses on the clear and present need to better correlate mechanistic insights from existing and emerging animal models of PH to specific etiologies and histopathologies of human PH. A better understanding of the pathologic processes in various animal models and how they relate to the human disease should accelerate the development of newer and more efficacious therapies.