USMLE Step 1 Web Prep — Respiratory System
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Chapter 13: Respiratory Pathology
PULMONARY INFECTIONS
BACTERIAL PNEUMONIA
Definition
  • Inflammation + consolidation
Clinical
  • Fever + chills
  • Productive cough
  • Tachypnea
  • Pleuritic chest pain
  • Decreased breath sounds
Lab
  • Elevated WBC count
Chest X-ray
  • Lobar
  • Bronchopneumonia
Clinical Keys
  • I.D. the organism
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LOBAR PNEUMONIA
Lobar consolidation
Organism
  • S.pneumoniae
  • Klebsiella- alcoholics
  • Four phases
  • Congestion
  • Red hepatization
  • Grey hepatization
  • Resolution
  • Red grey hepatization
Micro
  • exudates
/

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BRONCHOPNEUMONIA
General
  • Patchy consolidation
  • Young, old + terminally ill
  • Many organisms
Micro
  • Acute inflammation
Diagnosis
  • Sputum gram stain + culture
  • Blood cultures
Treatment
  • Empiric antibiotics
Complications
  • Scarring + adhesions
  • Abscess
  • Empyema
  • Sepsis
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ATYPICAL PNEUMONIA
Definition
  • Interstitial pneumonitis
Organism
  • Mycoplasma pneumonia
Kids and Young adults
Lab
  • Cold agglutinins
Micro
  • Lymphoplasmacytic inflammation
Chest X-ray
  • Interstitial infiltrates
Complications
  • Superimposed bacterial infections
  • Reye’s syndrome
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TUBERCULOSIS
Incidence
  • Increasing due to AIDS
Transmission
  • Inhaled bacilli
Clinical
  • Fever + night sweats
  • Weight loss
  • Cough
  • Hemoptysis
Micro
  • Caseating granulomas
  • Acid-fast bacilli
Lab
  • + PPD
/

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PRIMARY PULMONARY TUBERCULOSIS
 Initial exposure
 Ghon focus
 Ghon complex
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SECONDARY PULMONARY TUBERCULOSIS
 Reactivation or reinfection
 Simon focus- apex
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PROGRESSIVE PULMONARY TUBERCULOSIS
 Cavitary
 Miliary
 Tuberculous bronchopneumonia
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MILIARY SYSTEMIC SPREAD
 Meninges
 Cervical LN
 Lungs, pericardium, kidney, liver/spleen + ileum
 Pott’s disease – lumbar vertebrae
 GU system /

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SARCOIDOSIS
Epidemiology
  • Unknown etiology
  • African American females
Clinical
  • May be asymptomatic
  • SOB
  • Eye irritation
  • Fever/ night sweats
Noncaseating granulomas
  • Lung
  • Hilar LN
  • Eyes
  • Bone marrow
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SARCOIDOSIS CON’T
Lab
  • Elevated ACE
X-ray
  • Bilateral hilar lymphadenopathy
Micro
  • Noncaseating granulomas
  • Schaumann bodies
  • Asteroid bodies
Prognosis
  • Favorable/ Variable
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OBSTRUCTIVE VS RESTRICTIVE LUNG DISEASE

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CHRONIC OBSTRUCTIVE PULMONARY DISEASE
CHRONIC BRONCHITIS
Clinical
  • Persistent cough with sputum
  • 3 months in 2 consecutive years
Association
  • Smoking
Clinical
  • Cough
  • Frequent infections
  • Hypoxia + cyanosis
Micro
  • Hypertrophy of muscus glands
  • Increased goblet cells + mucus
  • Squamous metplasia + dysplasia
Complications
  • Risk of infection
  • Pulmonary HTN Cor pulmonale
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EMPHYSEMA
Definition
  • Destruction of alveolar septa
  • Loss of recoil
Etiology
  • Protease (elastase)/ antiprotease(1-antitrypsin) imbalance
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EMPHYSEMA CON’T
MANIFESTATIONS RELATED TO AREA OF INVOLVEMENT

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EMPHYSEMA CON’T
Gross
  • Enlarged lung
  • Visible air spaces
  • Apical blebs
Clinical
  • Dyspnea
  • Pursed lips
  • Accessory muscle use
  • Barrel chest
/

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ASTHMA
Definition
  • Reactive airways
Extrinsic
  • Allergic
  • Childhood + young adults
Intrinsic
  • Infections
  • Stress + exercise
  • Cold temperature
  • Drugs
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ASTHMA CON’T
Asthma attack
  • Wheezing, dyspnea + coughing
Status asthmaticus
  • Unrelenting
  • Fatal
Sputum cytology
  • Curschmann’s spirals
  • Eosinophils
  • Charcot-leydon crystals
Micro
  • Mucus gland hypertrophy + plugs
  • Eos
  • Edema
  • Smooth muscle hypertrophy
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BRONCHIECTASIS
Definition
  • Chronic necrotizing infections Airway dilatation
Causes
  • Bronchial obstruction
  • Necrotizing pneumonias
  • Cystic fibrosis
  • Kartagener’s syndrome
Clinical
  • Malodorous sputum
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RESPIRATORY DISTRESS SYNDROMES
ADULT RESPIRATORY DISTRESS SYNDROME
Definition
  • Diffuse alveolar damage respiratory failure
Causes
  • Shock, sepsis, trauma, etc.
Clinical
  • Dyspnea + tachypnea
  • Hypoxia
  • Accessory muscle use
X-ray
  • “white-out”
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ARDS CON’T
Gross
  • noncompliant lungs
Micro edema + inflammation
  • loss of type I pneumocytes
  • hyaline membranes
Treatment
  • underlying cause
  • oxygen, PEEP, + mechanical ventilation
Prognosis
  • 50% mortality
/

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RESPIRATORY DISTRESS OF THE NEWBORN
Associations
  • Prematurity
  • Maternal diabetes
  • Multiple births
Defect
  • Surfactant deficiency
Clinical
  • Normal at birth respiratory distress
X-ray
  • “ground-glass”
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RESPIRATORY DISTRESS OF THE NEWBORN CON’T
Lab
  • L:S < 2
Micro
  • Atelectasis
  • Hyaline membranes
Prognosis
  • 30% mortality
Complications
  • BPD
  • Retrolental fibroplasia
Prevention
  • Delay labor
  • Steroids
  • Surfactant at birth
/

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PULMONARY NEOPLASIA
BRONCHIOGENIC CARCINOMA
Epidemiology
  • #1 cancer death
  • Increasing in women
  • 50-80 years old
Risk factors
  • Smoking
  • Pollution + Asbestos
Genetic mutation
  • C-myc
  • K-ras
  • TSG- p53 +Rb gene
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BRONCHIOGENIC CARCINOMA CON’T
Clinical
  • Cough + sputum
  • Weight loss
  • Hemoptysis
  • Recurrent pneumonias
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ADENOCARCINOMA
Epidemiology
  • Males
  • Weakest assoc. with smoking
  • Peripheral
  • Under pleura
  • Pigmented
Micro
  • Gland formation
  • Mucin production
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BRONCHOALVEOLAR CARCINOMA
Arises from terminal bronchioles + alveolar wall
Micro
  • Columnar tumor cells
  • Nondestructive
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SQUAMOUS CELL CARCINOMA
Epidemiology
  • Smokers
Gross
  • Centrally located
  • Metaplasia dysplasia neoplasia
Micro
  • Invasive nests
  • “squamous pearls”
  • intercellular bridges
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SMALL CELL CARCINOMA
General
  • Smoking
  • Early metastasis
Micro
  • Sheets/nests of small round cells
EM
  • Neurosecretory granules
Associated with paraneoplastic syndromes
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PATTERN OF SPREAD OF LUNG CANCER
Intrathoracic spread
  • Lymph nodes
  • Pleura- adenocarcinoma
  • SVC syndrome
  • JVD
  • Edematous upper extremities
  • Plethora
  • Esophageal obstruction
  • Recurrent laryngeal n. involvement hoarseness
  • Phrenic n. involvement diaph. Paralysis
Extrathoracic spread
  • Adrenal
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PARANEOPLASTIC SYNDROMES
 Endocrine/metabolic syndromes
 Eaton- Lambert
 Acanthosis nigricans
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LUNG CANCER TREATMENT
Non-small cell cancer
  • Surgery
Small cell
  • Chemo + radiation
Prognosis
  • Poor
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BRONCHIAL CARCINOID
Epidemiology
  • Age<40
Gross
  • Polypoid intrabronchial mass
Micro
  • Small round cells organoid pattern
EM
  • Neurosecretory granules
/

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METASTATIC CARCINOMA TO THE LUNG
Epidemiology
  • Most common lung malignancy
Gross
  • Multiple nodules
Common primary sites
  • Breast
  • Stomach
  • Pancreas
  • Colon