Pseudohypoaldosteronism in a child with Down syndrome. Long-term management of salt loss by ion exchange resin administration

Pseudohypoaldosteronism type 1: clinical features and management in infancy

Type 1 pseudohypoaldosteronism (PHA) is a rare heterogeneous group of disorders characterised by resistance to aldosterone action. There is resultant salt wasting in the neonatal period, with hyperkalaemia and metabolic acidosis. Only after results confirm isolated resistance to aldosterone can the diagnosis of type 1 PHA be confidently made. Type 1 PHA can be further classified into i) renal type 1 (autosomal dominant (AD)) and ii) multiple target organ defect/systemic type 1 (autosomal recessive (AR)). The aim of this case series was to characterise the mode of presentation, management and short-term clinical outcomes of patients with PHA type 1. Case notes of newly diagnosed infants presenting with PHA type 1 were reviewed over a 5-year time period. Seven patients were diagnosed with PHA type 1. Initial presentation ranged from 4 to 28 days of age. Six had weight loss as a presenting feature. All subjects had hyperkalaemia, hyponatraemia, with elevated renin and aldosterone levels. Five patients have renal PHA type 1 and two patients have systemic PHA type, of whom one has had genetic testing to confirm the AR gene mutation on the SCNN1A gene. Renal PHA type 1 responds well to salt supplementation, whereas management of patients with systemic PHA type 1 proves more difficult as they are likely to get frequent episodes of electrolyte imbalance requiring urgent correction.

Hormone-nuclear receptor interactions in health and disease. Mineralocorticoid resistance

Mineralocorticoid resistance, or pseudohypoaldosteronism (PHA), is a rare cause of salt wasting in young children. It may be inherited as an autosomal dominant or recessive trait, it may occur sporadically or, rarely, it may develop secondary to other conditions. It is characterized by episodes of dehydration and hyponatraemia in the face of high aldosterone levels. In most cases, after a short period of salt supplementation no further ill effects are experienced. The condition is of great interest because it provides insights into both the mechanisms by which salt and water balance are controlled and the actions of aldosterone. This article reviews the normal physiology of aldosterone, with particular reference to its biosynthesis and its actions in specific target tissues. Current knowledge regarding the molecular mechanisms involved in aldosterone action is discussed in some detail. The clinical features of PHA are reviewed and diagnostic issues and clinical management considered. Finally, current views regarding the pathophysiology of the condition are presented. Here, considerable uncertainty remains. Whilst in many cases of PHA there is greatly reduced binding of aldosterone to its receptor, the underlying abnormality is yet to be identified; in particular, in spite of strong reasons for suspecting a defect or defects in the mineralocorticoid receptor, there is so far no direct evidence to support this hypothesis. The article concludes with a discussion of other possible explanations for the underlying abnormality in PHA.

Lack of effect of aldosterone on intracellular sodium and potassium in mononuclear leucocytes from patients with pseudohypoaldosteronism

In three patients with pseudohypoaldosteronism the effects of aldosterone on intracellular sodium and potassium were studied and compared with normal controls in whom aldosterone prevents the loss of sodium and potassium in vitro. Mononuclear leukocytes were incubated with or without aldosterone (1.4 nM) in RPMI-1640 for 1 h at 37 degrees C. After two washes in isotonic MgCl2 the wet cell pellets were weighted and intracellular sodium and potassium determined by flame photometry, results are expressed as mmol/kg wet cells. In the patients intracellular sodium fell from 18, 23 and 29 mmol/kg to 14, 18 and 11 mmol/kg, respectively, in the absence of aldosterone. With aldosterone added to the incubation medium sodium was not different from values obtained without aldosterone (15, 20 and 13 mmol/kg). Corresponding values for potassium were 89, 48 and 75 mmol/kg before and 68, 32 and 51 mmol/kg after incubation without and 69, 36 and 54 mmol/kg after incubation with aldosterone. Thus, incubation with aldosterone did not show an effect on intracellular sodium and potassium as seen in normals. Baseline values of sodium and potassium before the incubation were within the normal range. From these results it is concluded that in patients with pseudohypoaldosteronism the absent or decreased number of mineralocorticoid receptors in mononuclear leucocytes are accompanied by a lack of response of intracellular sodium and potassium to aldosterone in vitro. However, normal baseline intracellular electrolyte concentrations in these patients may indicate that mineralocorticoids are not involved in the maintenance of normal levels of intracellular sodium and potassium.

Pseudohypoaldosteronism: decreased aldosterone levels with age without significant change in urinary sodium excretion

To clarify age-related changes in the plasma renin activity (PRA)-aldosterone (ALDO) system in relation to urinary sodium (Na) excretion in pseudohypoaldosteronism type I (PHA), we followed a patient with PHA serially by measuring the hormonal balance and urinary electrolyte excretion for 5 years. The patient was diagnosed as PHA mainly on the basis of extremely high PRA (170 ng/ml/h) and ALDO (1670 ng/dl) despite massive urinary Na excretion, a normal ALDO/PRA ratio (mean value = 11), and the ineffectiveness of 9 alpha-fluorocortisol (Florinef) to reduce urinary Na excretion and PRA-ALDO. The pattern of reduction in PRA-ALDO with age in this patient was almost identical with that of normal infants and children and was most remarkable during the first 18 months of life. During this period, there were statistically significant correlations between age and each of the following values: PRA (r = -0.753, n = 9, P less than 0.05), ALDO (r = -0.736, n = 11, P less than 0.01) and urinary ALDO excretion (r = -0.840, n = 9, P less than 0.01). But the reduction of PRA-ALDO in this patient was not the result of increased urinary Na excretion with age. Although PRA and ALDO values in this patient did decrease with age, they were still high compared with age-matched controls, suggesting a marginal state of Na balance. Thus, we conclude that PRA-ALDO levels in PHA decrease with age in the same pattern as in normal infants and children without a significant change in urinary Na excretion, possibly through increased renal conservation of Na, the mechanism of which should be clarified in a future study.