A 10-month-old boy weighing 3 kg has polyuria, polydipsia and delayed motor milestones. His blood pressure is normal. Blood tests reveal: creatinine 80 mmol/l, sodium 128 mmol/l, chloride 90 mmol/l, potassium 3.0 mmol/l, calcium 2.7 mmol/l, bicarbonate 26 mmol/l and pH 7.46. Ultrasonography shows medullary nephrocalcinosis.
What is the most likely diagnosis?
A . Renal tubular acidosis
B . Bartter’s syndrome
C . Pseudohypoaldosteronism
D . Diabetes insipidus
Answer: B
Explanation:
Bartter’s syndrome Features of Bartter’s syndrome are hypokalemia, metabolic alkalosis and hypercalciuria. It is an autosomal-recessive condition leading to tubular defects in sodium chloride transport and increased intrarenal production of PGE2. The blood pressure is normal while the plasma renin and aldosterone levels are raised. Renal stones and nephrocalcinosis are common in this condition. In diabetes insipidus the loss of water raises sodium and potassium levels. Liddle’s syndrome is characterized by potassium wasting, hypokalemia and alkalosis, but is associated with low renin and aldosterone production and high blood pressure. In pseudohypoaldosteronism, the sodium level is decreased and potassium is elevated.