Hypochloremic Metabolic Alkalosis in an Infant with Diarrhea

Introduction: Congenital chloride diarrhea is an autosomal recessive disorder caused by mutations in genes encoding the intestinal epithelial Cl-/HCO3- exchanger, resulting in excessive chloride-rich diarrhea, dehydration, hypoelectrolytemia, and metabolic alkalosis. It is crucial to distinguish congenital chloride diarrhea, a rare cause of pseudobartter syndrome, from Bartter syndrome. Early diagnosis is vital for effective treatment due to its several intestinal and extraintestinal complications. Case Presentation: A 13-month-old female patient presented with vomiting, diarrhea, and growth failure. She was initially misdiagnosed with Bartter syndrome and was treated with indomethacin. The patient exhibited hypokalemic hypochloremic metabolic alkalosis, proteinuria, and increased echogenicity of the kidneys with loss of corticomedullary differentiation. Hypoelectrolytemia could not be corrected with indomethacin, and diarrhea persisted after treatment for viral gastroenteritis. Urine chloride levels were low despite low serum chloride levels, while fecal sodium and chloride levels were high. Genetic analysis revealed a homozygous SLC26A3 mutation of c.559G>T, consistent with congenital chloride diarrhea. Our aim was to normalize serum electrolytes, metabolic alkalosis, and proteinuria through fluid/electrolyte replacement, which also improved the patient’s growth and development. Conclusions: Watery stool may be mistaken for urine output by parents of infants with congenital chloride diarrhea. A low urine chloride level despite hypochloremia is the most valuable test for differential diagnosis. Moreover, chronic hypovolemia can cause proteinuria and renal damage. Differential diagnosis of cases with hypoelectrolytemic metabolic alkalosis is essential to prevent significant morbidity and mortality.