What is a common sign of cystic fibrosis?

A common sign of cystic fibrosis is the production of thick, sticky mucus that can lead to blockages in various parts of the body, particularly the lungs and digestive system. This characteristic mucus results from a genetic defect that affects the cystic fibrosis transmembrane conductance regulator (CFTR) protein involved in the movement of salt and water across cell membranes. When the CFTR protein is not functioning correctly, the mucus in the lungs becomes overly viscous, making it difficult to clear, resulting in frequent lung infections and obstructed airways. In the digestive system, this thick mucus can block the pancreatic ducts, preventing digestive enzymes from reaching the intestines and leading to nutrient absorption issues.

Other symptoms of cystic fibrosis may include respiratory problems, difficulty gaining weight, and issues with digestion, but the defining feature is indeed the thick and sticky mucus that plays a critical role in the disease's complications.