Early View Phenotype and outcome of PAH patients carrying a TBX4 mutation

INTRODUCTION: TBX4 mutation cause small patella syndrome (SPS) and/or pulmonary arterial hypertension (PAH). The characteristics and outcomes of PAH associated with TBX4 mutations are largely unknown. METHODS: We report the clinical, functional, radiologic, histologic and haemodynamic characteristics and outcomes of heritable PAH patients carrying a TBX4 mutation from the French PH Network. RESULTS: Twenty patients were identified in 17 families. They were characterised by a median age at diagnosis of 29 (0-76) year-old and a female to male ratio of 3. Most of the patients were in NYHA functional class III or IV (70%) with a severe hemodynamic impairment (median pulmonary vascular resistance of 13.6 [6.2-41.8] Wood Units). Skeletal signs of SPS were present in 80% of cases. Half of the patients had mild restrictive or obstructive limitation and diffusing capacity for carbon monoxide was decreased in all patients. High-resolution computed tomography showed bronchial abnormalities, peri-bronchial cysts, mosaic distribution and mediastinal lymphadenopathies. PAH therapy was associated with significant clinical improvement. At follow-up (median 76 months), two patients died and two underwent lung transplantation. One-, three- and five-year event-free survival rates were 100%, 94% and 83%, respectively. Histologic examination of explanted lungs revealed alveolar growth abnormalities, major pulmonary vascular remodelling similar to that observed in idiopathic PAH, and accumulation of cholesterol crystals within the lung parenchyma. CONCLUSION: PAH due to TBX4 mutations may occur with or without skeletal abnormalities across a broad age range from birth to late adulthood. PAH is usually severe and associated with bronchial and parenchymal abnormalities.