Symptoms of Cystic Fibrosis
Cystic fibrosis presents with a characteristic triad of recurrent respiratory infections with chronic pulmonary symptoms, failure to thrive with steatorrhea (loose, foul-smelling fatty stools), and salty-tasting skin, with over 80% of patients having pancreatic insufficiency at diagnosis. 1, 2
Neonatal and Early Infancy Presentation
Meconium ileus is the first symptom in approximately 15-20% of children with CF, presenting as intestinal obstruction at birth that typically requires surgical correction. 1, 2, 3 This is diagnostic of CF and represents the earliest clinical manifestation. 4
Respiratory Manifestations
The pulmonary symptoms develop progressively and include:
- Chronic cough that typically becomes evident around 10.5 months of age, with 75% of children developing chronic cough by age 6 years 1, 2
- Recurrent wheezing that distinguishes itself from asthma by accompanying steatorrhea, failure to thrive, and chronic purulent drainage 2
- Recurrent lower respiratory tract infections, as acute viral infections in CF children commonly progress to bacterial infections requiring hospitalization 1, 2
- Chronic productive cough with thick, viscid mucus due to deficient chloride transport causing abnormally thick secretions 1
The underlying mechanism involves airway obstruction, neutrophil-dominated inflammation, and progressive pulmonary infections, with Pseudomonas aeruginosa infection occurring in approximately 20% of children by age 1 year. 1
Gastrointestinal Symptoms
Pancreatic insufficiency is present at diagnosis in over 80% of patients and increases to over 90% with age, causing: 1, 3
- Steatorrhea (loose, foul-smelling fatty stools) from fat malabsorption 1
- Chronic abdominal pain 1
- Failure to thrive, particularly common in infants and young children, with mean height-for-age Z-score approximately -1.0 standard deviation below reference mean at age 1 year 1
- Fat-soluble vitamin deficiencies (A, D, E, K) 1
Distinctive Physical Finding
Overly salty sweat results from defective salt reabsorption in sweat glands and can lead to electrolyte imbalance and dehydration in certain cases. 1, 2 This is the basis for diagnostic sweat chloride testing (≥60 mEq/L confirms diagnosis). 2
Multi-System Involvement
CF affects multiple organ systems beyond lungs and pancreas: 1
- Upper respiratory tract: chronic sinusitis
- Liver: potential hepatic involvement
- Genitourinary tract: males may have congenital absence of vas deferens 5
Clinical Pitfalls
The majority of CF symptoms are not specific to CF, leading to frequent misdiagnoses as food allergies, celiac disease, asthma, or bronchitis. 1 The key distinguishing feature is the combination of respiratory and gastrointestinal symptoms with salty skin, rather than isolated findings. 1, 2
Progressive respiratory decline occurs with age, with 15-25% of children having lung function below normal range by age 7 years, and respiratory failure being the primary cause of death in over 90% of CF patients. 1, 3