Patho respiratory

Respiratory Pathology

Acute Respiratory Distress Syndrome

• Symptoms: acute respiratory insufficiency that doesn’t respond to oxygen
• Causes: pneumonia, aspiration of gastric contents, sepsis, severe trauma
• Pathogenesis: damage to alveolar capillary membrane; neutrophils play a big role
• Morphology: “diffuse alveolar damage” with hyaline membranes
• Prognosis: bad (40% mortality)

Obstructive Lung Diseases

Emphysema

• Destruction/enlargement of airspaces
• Types:
  • Centriacinar emphysema: destruction of proximal acinus, worse in upper lobes of lung, caused by smoking
  • Panacinar emphysema: destruction of entire acinus, worse in lower lobes of lung, caused by alpha-1-antitrypsin deficiency

Chronic Bronchitis

• Definition: persistent, productive cough for ≥ 3 months in ≥ 2 consecutive years
• Pathogenesis: hypersecretion of mucous
• Causes: smoking (mostly) and pollution

Asthma

• Chronic inflammatory disease of airways leading to bronchial constriction
• Symptoms: wheezing, breathlessness
• Hallmarks: intermittent, reversible airway obstruction, chronic inflammation, increased mucus
• Triggers: allergens, infection, smoke, cold, exercise

Bronchiectasis

• Permanent dilation of bronchi and bronchioles due to chronic inflammation
• Secondary to: obstruction (tumor), congenital conditions (cystic fibrosis), bad pneumonia

Restrictive Lung Diseases

Idiopathic Pulmonary Fibrosis

• Patchy, progressive lung fibrosis
• Symptoms: gradual onset cough, dyspnea, respiratory failure and cor pulmonale within about 3 years
• Radiologic and histologic term: “usual interstitial pneumonia”

Vascular Diseases

Pulmonary Embolism

• Most arise from deep venous thromboses in leg veins
• Symptoms: shortness of breath, infarction, or asymptomatic
• Morphology: “saddle” embolism filling left and right pulmonary arteries

Infections

Pneumonia

• Infection of the lung parenchyma
• Risk factors: increased age, chronic disease, immune problems, impaired mucous clearing
• Causes: bacteria, viruses
• Different anatomic patterns, clinical settings
• Symptoms and prognosis:
  • Bacterial: acute-onset, shaking chills, fever, productive cough
  • Viral: much more variable, fever present, cough may be absent

Tuberculosis

• Leading cause of death in medically/economically deprived areas (3 million deaths/year)
• Cause: Mycobacterium tuberculosis
• Chronic, granulomatous disease primarily of lungs
• Spread by respiratory droplet
• Primary (initial) TB: Ghon complex (lung+LN)
• Secondary (reactivation) TB: Cavitating lung granulomas, “seeding” of other organs

Opportunistic Pneumonias

• Affect immunosuppressed patients (patients with AIDS, cancer, post-transplant)
• Unusual organisms:
  • Pneumocystis jiroveci
  • Aspergillus
  • Cytomegalovirus

Carcinomas

• Causes of lung cancer:
  • 80% of cases occur in active smokers or those who have stopped recently
  • Linear correlation between frequency of lung cancer and pack-years of cigarette smoking
  • However: lung cancer develops in only 10-15% of smokers