What are the causes of pulmonary hemorrhages?

Causes of Pulmonary Hemorrhages

Pulmonary hemorrhage can be classified into localized bleeding and diffuse alveolar hemorrhage, with causes ranging from infections and malignancies to autoimmune conditions and vascular disorders.

Localized Pulmonary Hemorrhage Causes

• Respiratory Infections: Acute respiratory tract infections, particularly pneumonia, are common causes of hemoptysis in outpatient settings 1
• Bronchiectasis: A leading cause of hemoptysis in tertiary care centers in North America and Europe 1
• Lung Cancer: One of the most common causes of localized pulmonary bleeding 2
• Tuberculosis: Remains the most prevalent cause of hemoptysis in developing countries 1
• Anticoagulant Therapy: Can lead to pulmonary bleeding, especially in patients with underlying lung pathology 2
• Pulmonary Embolism: Though uncommon, can present with hemoptysis due to lung infarction 1

Diffuse Alveolar Hemorrhage (DAH) Causes

Immune-Mediated Causes

• Small Vessel Vasculitis:

  • Microscopic polyangiitis
  • Wegener's granulomatosis (Granulomatosis with polyangiitis)
  • These are the most frequent systemic diseases causing DAH 3

• Anti-Glomerular Basement Membrane Disease:

  • Goodpasture's syndrome - characterized by linear immunofluorescent patterns along the glomerular and pulmonary alveolar basement membranes 4

• Connective Tissue Disorders:

  • Systemic lupus erythematosus
  • Rheumatoid arthritis
  • Scleroderma 5

• Antiphospholipid Antibody Syndrome: Can cause pulmonary hemorrhage through immune-mediated vascular damage 5

Non-Immune Causes

• Cardiovascular Conditions:

  • Congestive heart failure
  • Mitral stenosis
  • Pulmonary veno-occlusive disease 3, 1

• Drug-Induced Pulmonary Hemorrhage:

  • Cyclophosphamide can cause pulmonary hemorrhage as an adverse effect 6
  • Other cytotoxic drugs 3

• Coagulation Disorders:

  • Disseminated intravascular coagulation
  • Thrombocytopenia
  • Anticoagulant therapy 2

• Non-Thrombotic Pulmonary Embolism:

  • Fat embolism (from fractures, lipid infusions, bone marrow harvest)
  • Septic embolism (associated with right-sided endocarditis)
  • Foreign material embolism (catheters, guide wires, vena cava filters)
  • Amniotic fluid embolism 1

• Idiopathic Pulmonary Hemosiderosis: Particularly in infants and children 1

• Toxic Exposures:

  • Inhaled toxins
  • Chemical pneumonitis 3

• Neoplastic Conditions:

  • Pulmonary metastases
  • Lymphangitic carcinomatosis 5

Acute Idiopathic Pulmonary Hemorrhage in Infants

• Characterized by:
  • Abrupt onset of overt bleeding or blood in airway
  • Severe respiratory distress requiring mechanical ventilation
  • Diffuse pulmonary infiltrates on imaging 1
• May share risk factors with Sudden Infant Death Syndrome (SIDS) 1

Clinical Pearls

• Cryptogenic Hemoptysis: Approximately 20% of patients with hemoptysis have no identifiable cause despite extensive investigation 1
• Mortality Risk: Severe pulmonary bleeding has high in-hospital mortality despite optimal management 2
• Diagnostic Approach: In cases of diffuse alveolar hemorrhage, a systematic approach to identify underlying cause is crucial as early aggressive treatment can be life-saving 3
• Long-term Complications: Repeated episodes of diffuse alveolar hemorrhage can lead to organizing pneumonia, collagen deposition in small airways, and ultimately pulmonary fibrosis 5
• Follow-up: Patients with "cryptogenic" hemoptysis have an increased risk of lung cancer in subsequent years and should receive appropriate follow-up 2

Diagnostic Considerations

• Chest radiography may show diffuse bilateral infiltrates in DAH but has limited value in differential diagnosis 7
• Bronchoscopy is essential for localizing the bleeding source in localized hemorrhage 1
• Identification of hemosiderin-laden macrophages (>20% of pulmonary macrophages) on bronchoalveolar lavage is diagnostic of alveolar hemorrhage 1
• Renal function should be assessed in all cases of unexplained pulmonary hemorrhage to rule out pulmonary-renal syndromes 4