ESPE Abstracts

Background: Aldosterone is a steroid hormone synthesized in the zona glomerulosa of the adrenal cortex. It is important for homeostasis of plasma sodium and potassium levels. Isolated aldosterone synthase deficiency can result in acute salt-losing crisis, severe hyperkalemia, metabolic acidosis, and failure to thrive.

Case presentation: An 18-day-old boy, born to consanguineous parents, presented to our hospital for failure to thrive. Initial laboratory investigations revealed an acute salt-losing crisis with severe hyponatremia, hyperkalemia and metabolic acidosis. The patient was managed as acute adrenal insufficiency with fluid resuscitation and stress dose of intravenous hydrocortisone. Upon stabilisation, oral hydrocortisone, fludrocortisone with sodium supplement were started. After getting a normal serum 17-hydroxyprogesterone level and normal cortisol secretion was confirmed by low dose synacthen test, hydrocortisone was weaned off. The subsequent serial sodium and potassium levels were within normal range. Biochemical test results (available later) showed undetectable plasma aldosterone level and high plasma renin activity at presentation. Genetic analysis of the CYP11B2 gene identified a homozygous likely pathogenic variant c.922T>C p.(Ser308Pro), confirming the diagnosis of type 1 aldosterone synthase deficiency. Family studies confirmed that both parents are heterozygous carriers of the variant. Baby was discharged with fludrocortisone replacement and sodium chloride with normalized electrolytes level and was thriving well.

Conclusion: Aldosterone synthase deficiency is a very rare cause of isolated hypoaldosteronism due to mutation in the CYP11B2 gene. This diagnosis should be kept in mind in patients presenting with life-threatening salt-losing crisis in infancy apart from other more common causes such as 21-hydroxylase deficiency. Clinical progress of the patient and the response to treatment, together with the biochemical investigation findings enable the exclusion of 21-hydroxylase deficiency. The genetic study leads to confirmation of the definite diagnosis and guide future management approach and prognosis. The course of this disease is usually good with adequate fludrocortisone replacement. To the best of our knowledge, this is the first case confirmed in infancy in Hong Kong.