Negative sweat tests and cystic fibrosis

Area of Science:

• Pulmonology
• Genetics
• Pediatrics

Background:

• Chronic suppurative pulmonary disease presents diagnostic challenges.
• Cystic fibrosis (CF) is a genetic disorder affecting multiple organs.
• Pancreatic involvement is a common manifestation of CF.

Purpose of the Study:

• To describe two brothers with chronic pulmonary disease and differing cystic fibrosis presentations.
• To discuss the diagnostic implications of normal sweat tests in suspected cystic fibrosis cases.
• To highlight the variability of cystic fibrosis phenotypes.

Main Methods:

• Case study of two brothers with chronic suppurative pulmonary disease.
• Clinical evaluation including assessment of pancreatic involvement.
• Sweat testing for chloride levels.

Main Results:

• One brother presented with classical cystic fibrosis, pancreatic insufficiency, and abnormal sweat tests.
• The second brother exhibited incomplete pancreatic disease and repeatedly normal sweat tests.
• This case series illustrates a divergent clinical presentation within the same family.

Conclusions:

• Normal sweat tests do not exclude a diagnosis of cystic fibrosis, particularly in atypical presentations.
• Diagnostic considerations for cystic fibrosis should include clinical suspicion beyond sweat test results.
• Further investigation may be warranted in patients with chronic pulmonary and pancreatic symptoms despite normal sweat tests.