Friday, July 7, 2017

Infectious Diseases of the Thorax

This post is derived from notes I took during training. Any images are copyright their respective owners.

  • Aspiration causes pneumonitis with lower pH causing worse reaction.
  • The term 'Pneumonia' is reserved for bacterial super infection with positive cultures
  • Tuberculosis (TB)
    • Findings: variable, can see necrotic lymph nodes
    • Rasmussen aneurysm: aneurysm associated with TB cavity, supplied by systemic bronchial arteries. Can cause massive hemoptysis
    • Reactivation can look like tree in bud nodules with +/- cavitation

  • Miliary TB: 1-2 mm nodules throughout lung
  • Mycobacterium avium complex (MAC)
    • Findings:
      • Elderly white females (Lady Windemere syndrome if suppress cough) get upper lobe cavitary
      • Middle aged males smoker/EtOH get Nodular bronchiectatic forms with clustered centrilobular nodules sparing pleura, irregular bronchiectasis with vol loss, predilection for RML and lingula
  • Fungal infections
    • Present with parenchymal necrotizing granulomatous lesions and regional LA. After acute phase, lung lesions may calcify.
    • Histoplasmosis: can cause large calcification in mediastinum (fibrosing mediastinitis)
  • Pulmonary mycetoma
    • Fungal ball, usually immunocompetent patients with fungal elements colonizing a cavity caused by other disease processes
    • Findings: upper lobes. Hemoptysis secondary to fragile bronchial circulation which feeds cavity wall
  • Allergic bronchopulmonary aspergillosis (ABPA)
    • Demographics: associated with asthma, cystic fibrosis
    • Pathology: Type I IgE and Type III hypersensitivity to aspergillus colonizing bronchial lumen causing inflammation, which releases enzymes that break down bronchial walls
    • DI: central bronchiectasis. Excess mucus production → mucoid impaction
  • Invasive aspergillosis
    • Occurs in immunosuppressed patients
    • Can see confluent nodules with surrounding ground glass halo sign (hemorrhage)

  • Pneumocystis carinii pneumonia (PCP)
    • Demographics: associated with HIV/immunosuppressed patients
    • Pathology: Caused by Pneumocystis jiroveci virus
    • Findings: bilateral perihilar reticular/ground-glass opacities, may consolidate after 10 days. Cysts - upper lobe. Can get spontaneous pneumothorax
    • Nuclear Medicine: Gallium positive
    • DDx: Kaposi (Gallium negative)

  • Viral pneumonia
    • DI: Miliary nodules with ground glass opacities



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