Reversible severe pulmonary hypertension in obesity hypoventilation and Mohr syndrome

A young overweight patient with Mohr–Claussen Syndrome was admitted to our department with the clinical diagnosis of pulmonary hypertension complaining about dyspnea at rest and excessive daytime sleepiness. Pulmonary function testing indicated severe airflow limitation and respiratory insufficiency. Pulmonary artery (PA) pressure was markedly increased. Pulmonary embolism, Alpha-1-antitrypsin-deficiency, emphysema and anatomical obstructions were excluded. Polysomnography showed recurrent oxygen desaturations compatible with alveolar hypoventilations. Hypercapnic ventilatory response testing (HCVR) indicated a missing increase in minute ventilation when exposed to hypercapnia. After 6 weeks of nocturnal non-invasive ventilation therapy, her clinical condition markedly improved. Furthermore, PA pressure returned to normal values. HCVR testing showed an adequate response to hypercapnia. Mohr–Claussen syndrome is a rare genetic disease affecting the mouth, face and digits. Adult patients are usually very obese; exposing them at risk for obesity hypoventilation syndrome (OHS). OHS is described as a combination of obesity and awake arterial hypercapnia (PaCO₂ > 45 mmHg) in the absence of other known causes of chronic alveolar hypoventilation. Unclear pulmonary hypertension in overweight patients should raise the suspicion for OHS.