ISSN:
1432-198X
Keywords:
Key words: Renal tubular acidosis
;
Osteopetrosis
;
Carbonic anhydrase II deficiency
;
Bicarbonate reabsorption
;
Ammonium excretion
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract. Renal tubular acidosis with osteopetrosis is an autosomal recessive disorder due to deficiency of carbonic anhydrase II (CAII). A 3.5-year-old Egyptian boy with osteopetrosis and cerebral calcification had a persistent normal anion gap type of metabolic acidosis (plasma pH 7.26) and a mild degree of hypokalemia. A baseline urine pH was 7.0; ammonium (NH4 +) excretion was low at 11 μmol/min per 1.73 m2; fractional excretion of bicarbonate HCO3 (FEHCO3) was high at 9%, when plasma HCO3 was 20 mmol/l; citrate excretion rate was high for the degree of acidosis at 0.35 mmol/mmol creatinine. Intravenous administration of sodium bicarbonate led to a urine pH of 7.6, a FEHCO3 of 14%, a urine-blood PCO2 difference of 7 mmHg, NH4 + excretion fell to close to nil, and citrate excretion remained at 0.38 mmol/mmol creatinine. Intravenous administration of arginine hydrochloride caused the urine pH to fall to 5.8, the FEHCO3 to fall to 0, the NH4 + excretion rate to rise to 43 μmol/min per 1.73 m2, and citrate excretion to fall to 〈0.01 mmol/mmol creatinine. These results show that our patient had a low rate of NH4 + excretion, a low urine minus blood PCO2 difference in alkaline urine, and a low urinary citrate excretion, but only when he was severely acidotic. He failed to achieve a maximally low urine pH. These findings indicate that his renal acidification mechanisms were impaired in both the proximal and distal tubule, the result of his CAII deficiency.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004670050354
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