Endocrine Abstracts

Salt-losing conditions can be challenging to manage well in infancy and early childhood. We describe a child with both salt-wasting 21-hydroxylase deficiency (SW21OHD) and cystic fibrosis (CF).

A male infant, JW, birth weight 3.5 kg, presented with a salt-wasting crisis on day 9 of life with hyponatraemia, hyperkalaemia, and weight loss of 415 g. Serum 17-hydroxyprogesterone (17OHP) was >1000 nmol/l and a diagnosis of SW21OHD was made. Neonatal screening confirmed the co-existence of CF (pancreatic sufficient). JW was established on treatment with hydrocortisone (HC) (13 mg/m² per day) fludrocortisone (FC) (300 μg/day), salt supplements 4 mmol/kg per day and flucloxacillin.

Throughout infancy, measurements of serum Na⁺, K⁺, and systolic BP were within normal limits. However, plasma renin activity (PRA) was elevated, particularly following the introduction of proprietary low-salt weaning foods. This was associated with poor weight gain, reaching a nadir of 7.5 kg (^-2.3 SDS) at 0.9 years. FC dose was increased to 400 μg/day but with little beneficial effect. Salt supplementation was increased gradually, reaching a maximum daily salt intake of 11 mmol/kg per day at 2 years of age. FC dose was decreased gradually to 200 μg/day in view of its potential growth suppressing effects. At 3.9 years, JW’s weight had increased to 15.6 kg (−0.3 SDS), height 98.1 cm (−0.8 SDS), height velocity 6.6 cm/year, PRA within normal limits.

This case highlights a number of important issues: i) The importance of providing adequate salt in babies with salt-wasting conditions to allow optimal growth. ii) The importance of continuing to monitor salt intake during weaning. iii) The relationship between salt intake, FC dose and PRA and their relative roles in the optimal management of SW21OHD. iv) The possible role of salt depletion in growth failure in infants and children with cystic fibrosis.