Cystic Fibrosis (CF) : Definition, Causes, Genetics, Foundation, Symptoms, Diagnosis, Management, & Life Expectancy
Definition
- Cystic Fibrosis is an inherited life-threatening multisystem disorder that damages the lungs and digestive system.
- Cause of death: Pneumonia
- Inheritance: Autosomal recessive
- Gene: Transmembrane conductance regulator (CFTR) gene on chromosome 7 which codes chloride channel in epithelial surfaces.
- Mutation: ΔF 508 (most common)
- More commonly seen in ashkenazi jews mediterranean population.
Clinical Features
1. Respiratory involvement
Absence or abnormal chloride channel
⇓
Dehydration of secretion
Nasal polyp
Sinusitis
Recurrent pneumonia
⇓
- Most common cause of recurrent pneumonia in cystic fibrosis overall: Pseudomonas (Mucoid > Non mucoid)
- Most common cause of recurrent pneumonia in cystic fibrosis in children: Staphylococcus aureus > Pseudomonas
- Fungal cause: Aspergillus fumigatus
2. GIT involvement
– Meconium ileus (doesn’t pass meconium after 48 hour of birth)
– Constipation
– Dehydration of pancreatic secretion because of
- Malabsorption (due to enzyme deficiency)
- Pancreatic duct & acinar destruction (due to pancreatitis autocatalytic activation of trypsinogen
– Biliary tract
- Gall stones
- Biliary cirrhosis
3. Sweat glands
- Function: To absorb chloride
Mutation in cystic fibrosis cause
- Excess salty sweats
- Dehydration
- Hypochloremic alkalosis severe cases
4. Genitourinary system
- Males: Sterility because of congenital absence of vas deferens
- Females: Reduced fertility because of thick cervical mucous
Investigations
Screening tests
- Sweat chloride test
⇓
Positive if chloride secretion > 60 meq/l
- Immunoreactive trypsinogen assay (neonates)
Diagnostic
Presence of clinical features of cystic fibrosis
OR
First degree relative with CF
OR
Positive sweat chloride test
+
Two cystic fibrosis mutations on DNA analysis
OR
Single abnormal nasal potential difference measurement
OR
Two sweat chloride test positive on two separate occasions
Treatment
1. Chest physiotherapy
2. Pneumonia
Oral / IV antibiotics
+
Nebulized / inhaled antibiotics
3. Enzyme therapy
- Orally 1–2 hour before each meal (life long)
Note: New therapy: Gene therapy
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