A Study of Sotatercept (MK-7962) in Japanese Children With Pulmonary Arterial Hypertension (PAH) (MK-7962-032)

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has pulmonary arterial hypertension (PAH, World Health Organization Group 1) confirmed by a prior right heart catheterization * Has idiopathic, heritable, drug- or toxin-induced PAH, connective tissue disease-associated PAH, repaired congenital heart disease-associated PAH, or PAH with coincidental shunt * Has PAH classified as World Health Organization Functional Class I, or symptomatic World Health Organization Functional Class II to IV * Has been receiving stable standard-of-care background therapy for PAH for at least 90 days * Is Japanese Exclusion Criteria: The main exclusion criteria include but are not limited to the following: * History of left-sided heart disease * Has severe congenital or developmental abnormalities of the lung, thorax, and/or diaphragm * History of Eisenmenger syndrome, Potts shunt, or recent atrial septostomy within 180 days * Has unrepaired or residual cardiac shunt with Qp/Qs \>1.5 * Has pulmonary veno-occlusive disease, pulmonary capillary hemangiomatosis, or overt signs of pulmonary capillary and/or venous involvement * PAH associated with portal hypertension * Known visceral arteriovenous malformations * History of full or partial pneumonectomy * Untreated more than mild obstructive sleep apnea * History of known pericardial constriction * Family history of sudden cardiac death or long QT syndrome * History of symptomatic coronary disease within 6 months or cerebrovascular accident within 3 months * Prior treatment with sotatercept or luspatercept