SERPINA1 and pulmonary arterial hypertension: The frequency of heterozygotes in the Russian population was 16.87% or 1:6 (CI95%: 14.76–19.00% by Clopper-Pearson exact method): in CFTR—2.81% (1:36), PAH—2.33% (1:43), SERPINA1—4.90% (1:20), and GJB2—6.83% (1:15).