Cystic fibrosis is associated with:
**Core Concept**
Cystic fibrosis is a genetic disorder characterized by the production of thick, sticky mucus due to mutations in the CFTR gene, leading to respiratory and digestive complications. The CFTR gene encodes for a chloride channel that regulates the transport of chloride ions across epithelial cell membranes.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of cystic fibrosis. In cystic fibrosis, the defective CFTR protein leads to an imbalance in chloride and sodium ion transport across epithelial cells, resulting in the production of thick, dehydrated mucus. This mucus clogs the airways and digestive tract, causing respiratory and gastrointestinal complications.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is not directly related to cystic fibrosis. While cystic fibrosis patients may have respiratory problems, the association with option A is not relevant to the underlying pathophysiology.
* **Option B:** This is incorrect because cystic fibrosis is not primarily associated with an overactive immune response. While patients with cystic fibrosis may develop secondary infections, the primary defect lies in the CFTR gene, not an overactive immune response.
* **Option C:** This is incorrect because cystic fibrosis is not primarily associated with an imbalance of potassium ions. While cystic fibrosis patients may have electrolyte imbalances, the primary defect lies in the CFTR gene, which regulates chloride ion transport, not potassium ions.
**Clinical Pearl / High-Yield Fact**
Cystic fibrosis patients often have a salty sweat due to the abnormal ion transport associated with the disease. This is a classic clinical correlation that can be used to diagnose cystic fibrosis.
**Correct Answer:** B.