Can intravesical BCG (Bacillus Calmette-Guérin) installation cause hypersensitivity pneumonitis?

Intravesical BCG Can Cause Hypersensitivity Pneumonitis

Yes, intravesical BCG installation can cause hypersensitivity pneumonitis as a rare but serious systemic complication of treatment. 1, 2, 3

Mechanism and Presentation

• BCG induces a systemic non-specific immunostimulatory response leading to secretion of pro-inflammatory cytokines, which can trigger hypersensitivity reactions beyond the bladder 4
• The immune response includes activation of neutrophils, monocytes, macrophages, T cells, and natural killer cells, which can lead to granulomatous inflammation in the lungs 4
• Symptoms typically include dyspnea, cough, and fever that develop after BCG instillation cycles 1
• Radiographic findings often show multiple tiny nodules and ground-glass opacities in both lung fields 1
• Pulmonary function tests typically reveal a restrictive ventilatory defect with decreased diffusion capacity 1

Diagnosis

• Diagnosis is based on:
  • Temporal relationship between BCG instillation and onset of respiratory symptoms 2
  • Characteristic radiographic findings of diffuse infiltrates 1, 2
  • Histopathology showing noncaseating granulomas on lung biopsy 1
  • Exclusion of other causes of pneumonitis 2
• It's important to differentiate between hypersensitivity pneumonitis and actual disseminated BCG infection, as treatment approaches differ 5

Management

• Immediate suspension of BCG instillations is necessary when hypersensitivity pneumonitis is suspected 4, 6
• Treatment options include:
  • For confirmed hypersensitivity reaction without positive cultures: Corticosteroids are the mainstay of treatment 5
  • For suspected or confirmed disseminated BCG infection: Anti-tuberculosis therapy with rifampin, isoniazid, and ethambutol for 6-9 months 2
  • In cases where distinction is unclear, combination therapy with both anti-tuberculosis drugs and corticosteroids is often recommended 6, 2

Risk Factors and Prevention

• While BCG is generally well-tolerated, systemic side effects occur in less than 5% of patients 2
• Traumatic catheterization or instillation within 2 weeks of TURBT increases risk of systemic absorption 4, 6
• Patients should be monitored for persistent flu-like symptoms lasting more than 48-72 hours after instillation 4
• Symptom management with single-dose, short-term quinolones may help reduce adverse events but won't prevent hypersensitivity pneumonitis 4

Clinical Pearls

• Hypersensitivity pneumonitis should be considered in any patient receiving intravesical BCG who develops respiratory symptoms, particularly if they persist beyond the typical 48-72 hour period of flu-like symptoms 1, 2
• Early recognition and treatment are crucial to prevent progression to more severe respiratory compromise 2
• Patients with a history of BCG-induced hypersensitivity pneumonitis should not receive further BCG therapy 6
• Alternative intravesical agents should be considered for ongoing bladder cancer management in these patients 4