Genetic testing in pulmonary hypertension in adults and children
Authors: Playan Escribano J , Cruz Utrilla A , Rodriguez Ogando A , Gallego N , Sabate Rotes A , Ochoa Parra N , Tenorio J , Lozano Balseiro M , Perez Olivares C , Rezola Arcelus E , Lapunzina P , Plata Izquierdo B , Martinez Menaca A , Escribano Subias P , Del Cerro Marin M J 
Published: October 2024

Pathogenic genetic variants have been found in patients with different forms of pulmonary arterial hypertension (PAH). Our aim was to define the genetic background of patients with idiopathic PAH (IPAH), heritable PAH (HPAH), pulmonary veno-occlusive disease (PVOD) and PAH associated with congenital heart disease (PAH-CHD); both in adult and pediatric age.

REHAP and REHIPED are Spanish, voluntary, multicenter registries that include patients with PAH. REHAP started in 2007 and includes patients over 18 years of age. REHIPED started in 2009 and collects patients between 2 months and 18 years of age. Patients with IPAH, HPAH, PVOD and PAH-CHD who have undergone a genetic testing were included. 413 adults and 122 children were analyzed. From 2011, Sanger sequencing and multiplex ligation-dependent probe amplification were used to detect genetic variants in the BMPR2, TBX4, and KCNK3 genes. Since 2014, a next generation sequencing (NGS) panel of 21 genes was applied. In 2017 this panel was expanded to cover 35 genes, and in 2019, it was expanded to 37 genes. Since 2020, whole-exome sequencing has been applied for the previously followed-up patients without known pathogenic/likely pathogenic (P/LP) genetic variants, and for each incident case.

There was a statistically significant difference (p 0.031) in the etiologies among adults and children. The etiologies in adults were 242 (59%) IPAH, 25 (6%) HPAH, 83 (20%) PAH-CHD, 63 (15%) PVOD. The etiologies in children were 66 (54%) IPAH, 8 (7%) HPAH, 38 (31%) PAH-CHD, and 10 (8%) PVOD. The genetic testing had a variant in 121 (29%) adults (56% pathogenic, 9% likely pathogenic, 32% VUS) and 63 (52%) children (65% pathogenic, 16% LP, 19% VUS) (adults vs children p &lt; 0.001). BMPR2 was the most frequent variant in both populations, followed by EIF2AK4. Patients with HAPH and PVOD are more likely to have a genetic variant, while PAH-CHD are the less likely to have one; both in adults and children (p&lt;0.001). The etiology was reclassified after the genetic testing in 13% adults and 19% children (p 0.08); including 6 adults and 4 children initially classified as IPAH and then diagnosed of PVOD when a P/LP variant was found in EIF2AK4. Also, 5 children were initially diagnosed as IPAH and then reclassified as multisystemic disorders (4 NFU1 and 1 MECP2)

In conclusion, a significant number of patients with PAH have a variant in genetic testing, especially if they are diagnosed in pediatric age. BMPR2 is the most frequent variant in our cohort, followed by EIF2AK4. Knowing the genetic background of our patients enables a better classification and understanding of the disease. This is especially important in patients initially diagnosed of PAHI who are then classified as PVOD. Also, knowing the genetic background may help develop new treatments in the future.