Postmortem diagnosis of PPA2associated sudden cardiac death from dried blood spot in a neonate presenting with vocal cord paralysis

Biallelic variants in inorganic pyrophosphatase 2 (PPA2) are known to cause infantile sudden cardiac failure (OMIM #617222), but relatively little is known about phenotypic variability of these patients prior to their death. We report a 5-wk-old male with bilateral vocal cord paralysis and hypertension who had a sudden unexpected cardiac death. Subsequently, molecular autopsy via whole-genome sequencing from newborn dried blood spot identified compound heterozygous mutations in PPA2, with a paternally inherited, pathogenic missense variant (c.514G > A; p.Glu172Lys) and a novel, maternally inherited missense variant of uncertain significance (c.442A > T; p.Thr148Ser). This report expands the presenting phenotype of patients with PPA2 variants. It also highlights the utility of dried blood spots for postmortem molecular diagnosis.