Which disorder is characterized by increased chloride in sweat?

Which disorder is characterized by increased chloride in sweat?

• A. Multiple myeloma
• B. Hypoparathyroidism
• C. Cystic fibrosis
• D. Wilson disease

Answer: (C)

In cystic fibrosis, the CFTR chloride channel is defective, so chloride reabsorption in the sweat duct is reduced, causing sweat to have higher chloride (and sodium) concentrations. This elevated sweat chloride is detected by the sweat chloride test and is a classic diagnostic sign of CF, often with values well above the normal range (commonly above about 60 mmol/L). The other disorders listed do not involve this sweat gland chloride transport defect, so they do not produce increased sweat chloride.

In cystic fibrosis, the CFTR chloride channel is defective, so chloride reabsorption in the sweat duct is reduced, causing sweat to have higher chloride (and sodium) concentrations. This elevated sweat chloride is detected by the sweat chloride test and is a classic diagnostic sign of CF, often with values well above the normal range (commonly above about 60 mmol/L). The other disorders listed do not involve this sweat gland chloride transport defect, so they do not produce increased sweat chloride.