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Pseudohypoaldosteronism is a hereditary salt-wasting syndrome usually seen in infancy with weight loss, dehydration, and failure to thrive. The patho-physiologic origin of Pseudohypoaldosteronism is unknown. The defect could be related to the unresponsiveness of target organs to mineralocorticoids resulting in hypo-natremia, hyperkalemia, and markedly elevated plasma aldostcrone and renin levels. Red blood cell Na+, K+-ATP-ase activity was measured in a pair of twins with pseudo-hypoaldosteronism, in an unrelated child with hypoaldos-teronism, and in an age-matched group of 50 healthy infants and young children. The enzyme was assayed by a method that couples ATP hydrolysis with NADH oxidation. Plasma renin and aldosterone levels were measured by RIA. Red blood cell Na+,K+-ATPase activity in the twins with Pseudohypoaldosteronism was very low at the time of diagnosis (3 wk). In both twins a time-related gradual increase in enzyme activity was observed during the 1st mo of life, reaching control values between 6 and 8 mo of age. This increase was associated with both a reduction in salt requirement and clinical improvement. Plasma renin activity and aldosterone levels were very high at the time of diagnosis. Plasma renin activity reverted gradually to normal values, whereas aldosterone levels remained high throughout the follow-up period. The child with hypoal-dosteronism had normal Na+,K+-ATPase activity at diagnosis and during follow-up.

Renal artery stenosis was diagnosed in two adolescents with neurofibromatosis using Doppler ultrasound. The diagnosis was confirmed by angiography. The renal vascular lesion in neurofibromatosis usually affects the proximal segment of the artery, which is the part most optimally visualized by ultrasound. We suggest that Doppler ultrasound of the renal arteries may be a useful technique in the investigation of hypertensive children with neurofibromatosis.

Four patients with severe pseudohypoaldosteronism caused by multiple end- organ resistance to aldosterone had frequently recurring lower respiratory tract infections and persistently elevated sweat and saliva electrolyte values. The increased saliva electrolyte values in these patients probably affect normal mucociliary function in the respiratory tract and facilitate the occurrence of frequent lower respiratory tract involvement. Patients with pseudohypoaldosteronism may require treatment similar to that for cystic fibrosis to prevent long- term respiratory complications. (J P EDIATR 1994;125:752-5)