Cystic Fibrosis

  • Cystic Fibrosis Overview

    • Definition: Cystic Fibrosis (CF) is an autosomal recessive genetic disease affecting various body systems, notably the respiratory and gastrointestinal systems.

    Genetics of Cystic Fibrosis

    • Autosomal Recessive Inheritance:
        - Involves inheriting two mutated genes, one from each parent.
        - Both parents must be carriers of the gene mutation, often without symptoms themselves.
        - Probability of Inheritance:
          - 25% chance of inheriting the disease (both genes)
          - 50% chance of being a carrier (one gene)
          - 25% chance of being unaffected (no mutated genes)

  • Population Prevalence:
      - Most common in Caucasians of northern European descent.
      - Occurs in about 1 in 3,000 live births.
      - Approximately 3% of the Caucasian population are symptom-free carriers; around 25% of Northern European descendants are carriers.

  • Genetic Counseling:
      - Recommended for families with CF history.
      - Genetic testing identifies 30 to 100 mutations in the CF gene with high accuracy.

Pathophysiology of Cystic Fibrosis

  • CF is characterized by diverse clinical features affecting multiple systems:
      - Respiratory System:
      - Gastrointestinal System: including the small intestine, pancreas, and bile ducts.
      - Reproductive System
      - Skin

  • Respiratory Complications:
      - Increased viscosity of mucus secretions leads to mechanical obstruction.
      - Thick mucoprotein accumulates in glands and ducts, particularly in the respiratory tract and pancreas.

Diagnostic Evaluation for Cystic Fibrosis

  • Screening Procedures:
      - DNA Testing: To identify mutations in the CF gene.
      - Quantitative Sweat Chloride Test:
        - Normal sweat chloride content < 40 mEq/L.     - Diagnostic if > 60 mEq/L; > 40 mEq/L in infants suggests CF.

  • Additional Tests:
      - Stool Fat or Enzyme Analysis:
        - Assesses pancreatic insufficiency by measuring undigested fat or stool elastase.
        - Important for guiding treatment to prevent malabsorption and malnutrition.
      - Chest Radiography: For imaging on lung conditions.
      - History & Physical Examination: Essential for diagnostics.

Respiratory Manifestations of Cystic Fibrosis

  • General Manifestations:
      - Almost all CF patients exhibit respiratory symptoms, onset and severity vary.

  • Consequences of Mucus Stagnation:
      - Bacterial colonization and lung tissue destruction.
      - Tenacious secretions obstruct bronchi and bronchioles.

  • Effects on Gas Exchange:
      - Decrease in O2/CO2 exchange leads to:
        - Hypoxia: Chronic low oxygen levels; clubbing of fingers and toes results from cellular responses to hypoxia, including the release of growth factors such as PDGF and VEGF, stimulating new blood vessel growth and connective tissue proliferation.
        - Hypercapnia: Elevated CO2 levels in the blood.
        - Acidosis: High CO2 levels contribute to acid build-up in the body.

  • Long-Term Risks:
      - Compression of pulmonary blood vessels, progressing to pulmonary hypertension, respiratory failure, and potential death.

Infectious Pathogens Associated with Cystic Fibrosis

  • Common infectious organisms:
      - Pseudomonas aeruginosa
      - Burkholderia cepacia
      - Staphylococcus aureus
      - Haemophilus influenzae
      - Escherichia coli
      - Klebsiella pneumoniae

Gastrointestinal Manifestations of Cystic Fibrosis

  • Mechanisms of Dysfunction:
      - Thick secretions lead to blocked pancreatic ducts, resulting in cystic dilation, degeneration, and diffuse fibrosis.
      - Prevents pancreatic enzymes from reaching the small intestine (duodenum), causing:
        - Impaired digestion and absorption, particularly of fats leading to steatorrhea (fatty stool).
        - Impaired digestion and absorption of proteins.

  • Further Progressions:
      - Occurrence of pancreatic fibrosis, potentially leading to diabetes mellitus.
      - Focal biliary obstruction can cause biliary cirrhosis.

Reproductive Manifestations of Cystic Fibrosis

  • Men’s Health:
      - Congenital bilateral absence of the vas deferens (CBAVD), affecting sperm transport.

  • Women’s Health:
      - Increased cervical mucus density; potential for:
        - Delayed sexual development.
        - Absent or irregular menstruation cycles.
        - Infertility or sterility.

Clinical Manifestations of Cystic Fibrosis

  • Key clinical features include:
      - Pancreatic Enzyme Deficiency: Leading to malabsorption.
      - Progressive Chronic Obstructive Pulmonary Disease (COPD): Associated with recurrent infections.
      - Failure to Thrive: Notable increased weight loss despite increased appetite.
      - Respiratory Deterioration: Gradual decline in respiratory function.

  • Sweat Gland Dysfunction:
      - Due to the defective Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which affects chloride ion transport, leading to excess salt excretion in sweat.

Cystic Fibrosis Presentation

  • Respiratory Symptoms:
      - Wheezing, dry cough, obstructive emphysema, patchy atelectasis, cyanosis, clubbing of fingers and toes, recurrent bronchitis, and pneumonia.

  • Gastrointestinal Symptoms:
      - Excretion of undigested food resulting in bulky, foul-smelling stools; tissue wasting; potential rectal prolapse from straining.

  • Other Symptoms:
      - Delayed puberty in females; sterility in males; children noted to taste “salty”; risk of dehydration; hypoalbuminemia.

Management of Cystic Fibrosis

  • Respiratory Management:
      - Removal of Excess Mucus: Through chest physical therapy that includes deep breathing, vibration, percussion, and forced expiration.
      - Bronchodilator Medication: Administer prior to chest physiotherapy to facilitate mucus expectoration.
      - Aggressive Treatment of Pulmonary Infections: Utilization of home IV antibiotics and aerosolized antibiotics when necessary.

  • Medications:
      - Tricafta (tablets : twice daily); targets defective proteins improving lung function and mucus clearance.
      - Use of steroids and nonsteroidal anti-inflammatory medications.
      - Transplantation: Consider for severe cases.

  • Goals of Care:
      - Prevent/minimize pulmonary complications.
      - Ensure adequate nutrition to support growth.
      - Support adaptation to chronic illness.

GI Management of Cystic Fibrosis

  • Pancreatic Enzyme Replacement Therapy (PERT):
      - Required to manage malabsorption; given in pill form during meals.
      - Dietary Recommendations: High-protein, high-calorie diet; potential unrestricted fats (up to 150% RDA); adequate salt supplementation.
      - Management of Diabetes: Incorporate oral glucose-lowering agents or insulin when needed.

Endocrine Management of Cystic Fibrosis

  • Cystic Fibrosis-Related Diabetes (CFRD):
      - Characterized by insulin resistance and insulin deficiency, necessitating screening with oral glucose tolerance tests starting at age 10.
      - Continuous monitoring of glucose levels and overall bone health.

Family and Emotional Support

  • Emotional and Social Considerations:
      - Addressing the emotional needs of both the child with CF and their family is crucial due to frequent treatment requirements and hospitalizations.
      - Family dynamics influenced by the implications of genetic transmission of CF.
      - Importance of home care and support systems.

Prognosis for Cystic Fibrosis

  • Current Life Expectancy:
      - Decreased life expectancy for children with CF, estimated average age around 44 years.

  • Maximizing Health Potential:
      - Focus on nutrition, early aggressive infection treatment, and pulmonary hygiene practices.

  • Future Directions:
      - Advances in transplantation, gene therapy, and improved pharmacologic agents offer hope for better outcomes.