Unimpaired postnatal respiratory adaptation in a preterm human infant with a homozygous ENaC-α unit loss-of-function mutation.

The amiloride-sensitive epithelial sodium channel, ENaC, is thought to have a major role in clearing fluid from the alveoli immediately after birth. ENaC-α knockout mice die soon after birth from failure to clear their lungs of liquid. We report on a male infant born after 33 weeks of gestation with uneventful postnatal adaptation (Apgar 9/9/9 at 1, 5 and 10  min after birth) who did not require any respiratory support during his first days of life. At nine days of life, he became lethargic and hyperthermic, displaying low Na(+) (126  mmol l(-1)), high K(+) (8.9  mmol l(-1)), high aldosterone (3000  ng l(-1))and high renin (1000  ng l(-1)) plasma concentrations, commensurate with pseudohypoaldosteronism type I. He was found to be homozygous for the c.1678G>A mutation in the SCNN1A gene that codes for the ENaC-α unit. We conclude that clearance of alveolar fluid after birth in humans does not critically depend on ENaC.