Respiratory Tract Pathology Flashcards
Rhinitis
Inflammation of the nasal mucosa –> rhinovirus is the most common cause
- presents with sneezing, congestion and runny nose (common cold)
Allergic rhinitis is a subtype of rhinitis –> due to type I hypersensitivity reaction (e.g. to pollen)
- characterized by an inflammatory infiltrate with eosinophils
- associated with asthma and eczema
Nasal polyp
Protrusion of edematous, inflamed nasal mucosa
- usually secondary to repeated bouts of rhinitis; also occurs in CF and aspirin-intolerant asthma
- aspirin intolerant asthma –> characterized by the triad of asthma, aspirin induced bronchospasms, and nasal polyps
Angiofibroma
Benign tumor of nasal mucosa composed of large blood vessels and fibrous tissue
- classically seen in adolescent males
- presents with profuse epistaxis
Nasopharyngeal carcinoma
Malignant tumor of nasopharyngeal epithelium
- associated with EBV –> classically seen in african children and chinese adults
- biopsy usually reveals pleomorphic keratin positive epithelial cells (poorly differentiated squamous cell carcinoma) in a background of lymphocytes
Often presents with involvement of cervical lymph nodes
Acute epiglottitis
Inflammation of the epiglottis
- H. influenza type b is the most common cause, especially in non-immunized children
Presents with high fever, sore throat, drooling with dysphagia, muffled voice, and inspiratory stridor –> risk of airway obstruction
Laryngotraceobronchitis (croup)
Inflammation of the upper airway
- parainfluenza virus is the most common cause
Presents with a hoarse, barking cough and inspiratory stridor
Vocal cord nodule
Nodule that arises on the true vocal cord
- due to excessive use of vocal cords
- usually bilateral
- composed of degenerative (myxoid) connective tissue
Presents with hoarseness; resolves with resting of voice
Laryngeal papilloma
Benign papillary tumor of the vocal cord
- due to HPV 6 +11
- papillomas are usually single in adults and multiple in children
Presents with hoarseness
Laryngeal carcinoma
Squamous cell carcinoma usually arising from the epithelial lining of the vocal cord
Risk factors:
- alcohol
- tobacco
- can rarely arise from a laryngeal papilloma
Presents with hoarseness
- other signs include cough + stridor
Pneumonia
Infection of the lung parenchyma
- occurs when normal defenses are impaired (e.g. impaired cough reflex, damage to mucociliary escalator, or mucus plugging)
Clinical features
- fever and chills
- productive cough with yellow-green (pus) or rusty (bloody) sputum
- tachypean with pleuritic chest pain
- decreased breath sounds
- dullness to percussion
- elevated WBC count
Diagnosis –> made by chest x ray, sputum gram stain + culture, and blood cultures
3 patterns classically seen on chest x ray:
- lobal pneumonia
- bronchopneumonia
- interstitial pneumonia
Lobar pneumonia
Characterized by consolidation of an entire lobe of the lung
- usually bacterial –> most common causes are streptococcus pneumoniae (95%) + Klebsiella pneumoniae (5%)
Classic gross phases of lobar pneumoina:
- congestion –> due to congested vessels and edema
- red hepatization –> due to exudate, neutrophils and hemorrhage filling the alveolar air spaces, giving the normally spongy lung a solid consistency
- grey hepatization –> due to degradation of red cells within the exudate
- resolution
Bronchopneumonia
Characterized by scattered patchy consolidation centered around bronchioles
- often multifocal and bilateral
- caused by a variety of bacterial organisms
Interstitial (atypical) pneumonia
Characterized by diffuse interstitial infiltrates
- presents with relatively mild upper respiratory symptoms –> minimal sputum and low fever = atypical presentation
- caused by bacteria or viruses
Aspiration pneumonia
Seen in patients at risk for aspiration –> alcoholics + comatose patients
- most often due to anaerobic bacteria in the oropharynx –> bacteroides, fusobacterium + peptococcus
- classically results in a right lower lobe abscess –> anatomically, the right main stem bronchus branches at a less acute angle than the left
Causes of lobar pneumonia
- Strep pneumo –> most common cause of CA pneumonia and secondary pneumonia (bacterial pneumonia superimposed on a viral upper respiratory tract infection)
- usually seen in middle aged adults and the elderly - Klebsiella pneumoniae –> part of enteric flora that is aspirated, affects malnourished and debilitated individuals, especially elderly in nursing homes, alcoholics and diabetics
- thick mucoid capsule results in gelatinous sputum = currant jelly
- often complicated by abscess
Causes of bronchopneumonia
- Staph aureus –> 2nd most common cause of secondary pneumonia; often complicated by abscess or empyema
- Haemophilus influenzae –> common cause of secondary pneumonia and pneumonia superimposed on COPD (leads to exacerbation of COPD)
- Moraxella catarrhalis –> CA pneumonia and pneumonia superimposed on COPD (leads to exacerbation of COPD)
- Llegionella pneumophilia –> CA pneumonia, pneumonia superimposed on COPD, or pneumonia in immunocompromised states
- transmitted from water source
- intracellular organism that is best visualized by silver stain
Causes of interstitial/atypical pneumonia
- Mycoplasma pneumoniae –> most common cause of atypical pneumonia, usually affects young adults
- complications include autoimmune hemolytic anemia (IgM against I antigen on RBCs causes cold hemoltyic anemia) + erythema multiforme
- not visible on gram stain due to lack of cell wall - Chlamydia pneumoniae –> second most common cause of atypical pneumonia in young adults
- Respiratory syncytial virus (RSV) –> most common cause of atypical pneumonia in infants
- CMV –> atypical pneumonia with post transplant immunosuppressive therapy
- Influenza virus –> atypical pneumonia in the elderly, immunocompromised, and those with pre-existing lung disease
- also increases the risk for superimposed S. aureus or H. flu bacterial pneumonia - Coxeilla burnetti –> atypical pneumonia with high fever (Q fever), seen in farmers and vets
- coxiella spores are deposited on cattle by ticks or are present in cattle placentas
- coxiella is a rickettsial organism, but distinct from most rickettsiea because it…
- –> causes pneumonia
- –> does not require arthropod vector for transmission (survives as highly heat resistant endospores)
- —> does not produce a skin rash
Tuberculosis
- primary TB
Due to inhalation of aerozolized mycobacterium tuberculosis
Primary TB arises with initial exposure –> results in focal, caseating necrosis in the lower lobe of the lung and hilar lymph nodes that undergoes fibrosis and calcification, forming a Ghon complex
Secondary TB
Arises with reactivation of mycobacterium tuberculosis
- reactivation is commonly due to AIDS, may also be seen with aging
- occurs at apex of lung –> relatively poor lymphatic drainage + high oxygen tension
- forms cavitary foxi of vaseous necrosis, may also lead to miliary pulmonary TB or tuberculous bronchopneumonia
Clinical features
- fevers
- night sweats
- cough with hemoptysis
- weight loss
Biopsy revelas caseating granulomas; AFB stain reveals acid fast bacilli
Systemic spread often occurs and can involve any tissue –> common sites:
- meninges –> meningitis
- cervical lymph nodes
- kidneys –> sterile pyuriva
- lumbar vertebrae –> Pott disease
Basic principles of COPD
Group of diseases characterized by airway obstruction –> lung does not empty, and air is trapped
- volume of air that can be forcefully expired is decreased (decreased FVC), especially during the first second of expiration (very decreased FEV1) –> results in decreased FEV1: FVC ratio
- total lung capacity is usually increased due to air trapping
Chronic bronchitis
Chronic productive cough lasting at least 3 months over a minimum of 2 years –> highly associated with smoking
Characterized by hypertrophy of bronchial mucinous glands –> leads to increased thickness of mucus glands relative to bronchial wall thickness
- Reid index increases to >50%, normal is mucus plugs trap CO2 = increased PaCO2 + decreased PaO2
- increased risk of infection and cor pulmonale
Emphysema
Destruction of alveolar air sacs –> loss of elastic recoil and collapse of airway during exhalation results in obstruction and air trapping
Due to imbalance of protease and antiproteases
- inflammation in the lung normally leads to release of proteases by neutrophils and macrophages
- alpha1 antitrypsin (A1AT) neutralizes proteases
- excessive inflammation of lack of A1AT –> leads to destruction of the alveolar air sacs
Smoking is the most common cause of emphysema
- pollutants in smoke lead to excessive inflammation and protease mediated damage
- results in centriacinar emphysema that is most severe in the upper lobes
A1AT deficiency
A rare cause of emphysema
- lack of antiprotease leaves the air sacs vulnerable to protease-mediated damage
- results in panacinar emphysema that is most severe in the lower lobes
- liver cirrhosis may also be present
- –> A1AT deficiency is due to misfolding of the mutated protein
- –> mutated A1AT accumulates in the ER of hpatocytes, resulting in liver damage
- –> biopsy reveals pink, PAS-positive globules in hepatocytes
Disease severity is based on the degree of A1AT deficiency
- PiM = normal allele –> two copies are usually expressed
- PiZ = most common clinically relevant mutation –> results in significantly low levels of circulating A1AT
- PiMZ = heterozygotes are usually asymptomatic with decreased circulating levels of A1AT –> significant risk for emphysema with smoking exists
- PiZZ homozygotes –> significant risk for panacinar emphysema and cirrhosis