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Clinical Problem Solving: Radiology
January 2007

Radiology Quiz Case 1: Diagnosis

Author Affiliations

Copyright 2007 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.2007

Arch Otolaryngol Head Neck Surg. 2007;133(1):92. doi:10.1001/archotol.133.1.92

Based on the patient's clinical symptoms and radiographic findings, the operating surgeon suspected a diagnosis of CF and ordered a sweat test, which revealed an elevated sweat chloride concentration (104 mEq/L [reference range, 0-40 mEq/L]) and confirmed the diagnosis of CF.

Cystic fibrosis, which is autosomal recessive, is the most common lethal genetic disorder in the white population (1/2000).1 It is caused by a genetic defect on chromosome 7 that involves the CF transmembrane conductance regulator protein. As a result, there is a deficiency in chloride ion export from epithelial cells on the apical cell membrane in exocrine glands, specifically in the pancreatic ducts in the pancreas and respiratory epithelium located in the nasal cavity, sinuses, and tracheal bronchial tree. A decrease in membrane chloride permeability leads to an increased flow of neutralizing sodium in the cells, with passive free water absorption. Subsequently, dehydration of extracellular secretions can increase the viscosity of mucous in the excretory ducts, causing obstruction and entrapment of bacteria.1