Elevated sweat chloride levels are a hallmark of which condition?

Elevated sweat chloride levels are a hallmark of which condition?

• A. Cystic fibrosis
• B. Diabetes mellitus
• C. Hyponatremia
• D. Hemochromatosis

Answer: (A)

Elevated sweat chloride reflects a defect in epithelial chloride transport. In cystic fibrosis, mutations in the CFTR chloride channel impair reabsorption of chloride (and the accompanying sodium) in the sweat duct, so the sweat that reaches the skin is unusually salty. This results in consistently higher chloride levels in sweat samples, which is why the sweat chloride test is used diagnostically for this condition. In healthy individuals, most chloride is reabsorbed and sweat chloride is low; in cystic fibrosis, it remains high—usually above about 60 mmol/L—making this a hallmark feature. The other conditions listed involve different pathophysiology (glucose metabolism, serum sodium balance, iron storage) and do not produce this characteristic salty sweat.

Elevated sweat chloride reflects a defect in epithelial chloride transport. In cystic fibrosis, mutations in the CFTR chloride channel impair reabsorption of chloride (and the accompanying sodium) in the sweat duct, so the sweat that reaches the skin is unusually salty. This results in consistently higher chloride levels in sweat samples, which is why the sweat chloride test is used diagnostically for this condition. In healthy individuals, most chloride is reabsorbed and sweat chloride is low; in cystic fibrosis, it remains high—usually above about 60 mmol/L—making this a hallmark feature. The other conditions listed involve different pathophysiology (glucose metabolism, serum sodium balance, iron storage) and do not produce this characteristic salty sweat.