Which genetic disorder causes thick mucus production and chronic lung infections, often with gastrointestinal problems?

• A. Alpha-1 antitrypsin deficiency
• B. Cystic fibrosis
• C. Primary ciliary dyskinesia
• D. Chediak-Higashi syndrome

Answer: (B)

This tests recognizing a genetic condition that causes thick, sticky mucus in multiple organs due to a chloride channel defect. Cystic fibrosis arises from mutations in the CFTR gene, which impairs chloride and water transport across epithelial surfaces. In the lungs, the resulting dehydrated mucus clogs airways, promoting bacterial growth and leading to recurrent infections and chronic inflammation. In the digestive system, thick secretions can block pancreatic ducts, causing pancreatic insufficiency and malabsorption of fats, which leads to steatorrhea and deficiencies of fat-soluble vitamins, contributing to poor growth and GI problems. This combination of ongoing respiratory infections and gastrointestinal involvement is characteristic of CF. By comparison, alpha-1 antitrypsin deficiency mainly causes early lung disease without the abdominal mucus plugging and pancreatic involvement; primary ciliary dyskinesia involves immotile cilia with chronic respiratory infections but not the typical pancreatic GI features; Chediak-Higashi presents with immune issues and albinism rather than thick mucus–related GI problems.