[Mineralocorticoid resistance: pseudohypoaldosteronism type 1]

Systemic Pseudohypoaldosteronism Type 1 due to 3 Novel Mutations in SCNN1Aand SCNN1BGenes

OBJECTIVE

The systemic form of pseudohypoaldosteronism type 1 (PHA1) is an autosomal recessive disorder characterized by defective sodium transport in multi-organ systems. Mutations in the genes encoding the amiloride-sensitive epithelial sodium channel, ENaC, account for genetic causes of systemic PHA1. We describe systemic PHA1 due to 4 novel variants detected in SCNN1A and SCNN1B in 3 cases from 3 unrelated consanguineous families.

PATIENTS AND METHODS

We evaluated the clinical presentations, biochemical and hormonal characteristics, and molecular genetic analysis results of 3 patients from 3 unrelated consanguineous families and parents from whom samples were available.

RESULTS

The ages at presentation were postnatal days 9, 10, and 5. The main presentation symptoms were vomiting, poor feeding, weakness, weight loss, and skin rash. All patients exhibited laboratory characteristics including severe hyponatremia, hyperkalemia, metabolic acidosis, elevated plasma renin, elevated aldosterone, and positive sweat tests, suggesting a diagnosis of systemic PHA1. Molecular genetic analysis revealed 2 novel pathogenic variants [c.87C>A(p.Tyr29*)/IVS9 + 1G>A (c.1346 + 1G>A)] in SCNN1Bin case 1, a novel homozygous pathogenic variant [p.His69Arg(c.206A>G] in SCNN1Ain case 2, and a homozygous one-base duplication, p.A200Gfs*6 (c.598dupG), in SCNN1A in case 3.

CONCLUSION

PHA1 should be considered at differential diagnosis in patients presenting with hyponatremia, hyperkalemia, and metabolic acidosis. The cases in this report involving 4 novel variants will add valuable insights into the phenotype-genotype relationship and will expand the mutation database.

A case of systemic pseudohypoaldosteronism with a novel mutation in the SCNN1A gene

We report a neonatal case of systemic pseudohypoaldosteronism type 1 caused by a novel mutation in the SCNN1A gene (homozygous c.1052+2dupT in intron 3) in which the patient presented with life-threatening hyperkalemia, hyponatremia and metabolic acidosis. It remains uncertain if there is genotype-phenotype correlation, due to the rarity of the disease. This mutation, which to our best knowledge has not been described before, was associated with a very severe phenotype requiring aggressive therapy.