Endocrine Abstracts

Pseudohypoaldosteronism is a rare salt-wasting disorder of infancy characterised by hyponatraemia, hyperkalaemia and metabolic acidosis, with increased plasma renin activity and elevated aldosterone concentrations (1). We present three recent cases.

Case 1: An 8 day old female infant presented with poor feeding and vomiting. She was born to consanguineous parents. She was bradycardic, hypothermic and clinically shocked. Initial bloods showed hyponatraemia (sodium 116 mmol/l), hyperkalaemia (potassium >10 mmol/l) and metabolic acidosis. ECG revealed brief, unsustained runs of ventricular tachycardia. She required PICU admission. Further investigations revealed a markedly elevated aldosterone (45200 pmol/l) and renin (>34ng/ml/h), with normal cortisol and 17-OHP; suggesting a diagnosis of pseudohypoaldosteronism (PHA) - genetic testing was sent in view of consanguinity.

Case 2: An 11 week old male infant referred with faltering growth, poor feeding and frequent vomiting. Initial bloods showed significant hyponatraemia (sodium 103 mmol/l) and hyperkalaemia (potassium 6.9 mmol/l). The infant was dehydrated but normotensive and normoglycemic. Aldosterone (2891pmol/l) and renin (>500u/U/mL) were elevated with normal cortisol and 17-OHP. Urine grew Klebsiella pneumoniae and an ultrasound renal tract demonstrated right renal pelvic dilatation to 11mm.

Case 3: A 16 week old male infant also referred with faltering growth, otherwise well with no significant history. Initial sodium 124 mmol/l and potassium 6.3 mmol/l. The infant was hypotensive but glucose was normal. Again, aldosterone (>27800 pmol/L) and renin (>5000u/U/mL) were high with normal cortisol and 17-OHP. Urine grew Coliforms and an ultrasound renal tract demonstrated left renal pelvic dilatation to 10mm with dilation of the left ureter to the level of the VUJ. Given this biochemical picture important differential diagnoses include congenital adrenal hyperplasia, aldosterone synthase deficiency and adrenal hypoplasia congenita; which result in aldosterone deficiency. The genetic condition PHA-I is a heterogeneous syndrome that includes at least 2 clinically distinguishable entities with either renal or multiple target organ defects (MTOD). Case 1 is an example of MTOD PHA-I which shows autosomal recessive inheritance and is characterised by salt wastage from the salivary and sweat glands, respiratory tract and colon. Transient forms of pseudohypoaldosteronism can occur in infants with pyelonephritis and obstructive uropathy, as demonstrated by cases 2 and 3.