Sweat chlorides are increased in:
**Core Concept**
Chloride levels in sweat are a diagnostic tool for Cystic Fibrosis (CF), a genetic disorder affecting the respiratory, digestive, and reproductive systems. The underlying principle is the abnormal function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, leading to abnormal chloride transport across epithelial membranes.
**Why the Correct Answer is Right**
In healthy individuals, chloride ions are secreted into sweat through the CFTR protein, which is a chloride channel. In patients with Cystic Fibrosis, the mutated CFTR protein is dysfunctional, leading to an accumulation of chloride ions in the sweat. This results in increased chloride levels in sweat, which is a diagnostic hallmark of the disease. The abnormal chloride transport is due to the impaired function of the CFTR protein, which is encoded by the CFTR gene.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not relate to the underlying pathophysiology of Cystic Fibrosis. While it may be a distractor, it does not provide a plausible explanation for increased sweat chlorides.
**Option B:** This option is incorrect because it is unrelated to the diagnostic tool of sweat chloride testing. While it may be a relevant clinical condition, it is not the correct answer.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that a sweat chloride test result of ≥60 mmol/L is considered diagnostic for Cystic Fibrosis, while a result of 30-59 mmol/L is considered intermediate, and a result of <30 mmol/L is considered normal. This distinction is crucial for diagnosing and managing CF patients.
**Correct Answer: C. Cystic Fibrosis.**