Week 2: Pathology of COPD Flashcards
Definition of COPD
- disease characterized by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases
- major disorders: emphysema, chronic bronchitis, asthma
definition of emphysema
-permanent enlargement of the airspaces distal to the terminal bronchiole with destruction of the airspace walls and without obvious fibrosis
Definition of chronic bronchitis
a persistent productive cough of 3 months duration in at least 2 consecutive years
Centriacinar or centrilobular emphysema
- most common type. dilatation and destruction mainly involves proximal portion of acinus
- associated with heavy smoking
- can have emphysematous and normal airspaces found within same acinus
- more common in upper lobes
- walls of emphysematous airspaces often have black pigment
- often associated with chronic bronchitis-inflammation around bronchi and bronchioles common
Panacinar emphysema
- involves dilation and destruction of initially acinar structures distal to respiratory bronchioles but extends to whole acinus
- may be associated with alpha-1-antitrypsin deficiency or defects in elastin
- most common in lower zones and in anterior margins of the lung
Paraseptal or bullous emphysema
-most obvious near pleura, especially in upper 1/2 of lung
-often adjacent to areas of fibrosis or atelectasis
-associated with spontaneous pneumothorax in young people
-affects distal acinar
(pronounced cystic sub pleural dilatation=bullous disease —in any emphysema)
Pathogenesis of Emphysema
two processes important to formation of enlarged open spaces
- Septal Rupture
- irritants and toxic materials breathed in, trapped in airways
- triggers inflammatory response
- enzymes released damage alveolar walls (a1-antitrypsin plays role in controlling these enzymes)
- protease (mainly elastase)-antiprotease (a1-antitrypsin) imbalance
- ROS from PMNs have role in damage - Elastic recoil of surrounding tissue
- destruction of septal wall, with elastic recoil, pulls airspace wider
- surrounding airspaces collapse
- loss of elastic recoil of alveolus and narrowed bronchiole causes difficult expiration
Pathologic features of chronic bronchitis
- initial: hypertrophy of submucosal glands and goblet cell increase in epithelial lining of trachea and bronchi
- hypersecretion of mucus - inflammation (lymphocytic)
- hyperemia and edema
- increase in goblet cells in small airways
- increase in Reid index: submucosal gland thickness to distance between epithelial BM and perichondrium - narrowing/obstruction of bronchioles due to mucus, inflammation, fibrosis
- squamous metaplasia: from smoking
Reid index seen in chronic bronchitis
normally 0.4, a ratio grater than 0.5 seen in chronic bronchitis
bronchiolitis obliterans
severe cases of chronic bronchitis leading to lumenal obliteration
Pathogenesis of chronic bronchitis
chronic irritation from inhaled substances such as tobacco smoke or silica dust
-infections are secondary in initiating disease process, helps maintain it
asthma definition
- chronic relapsing inflammatory disorder of the airways
- reversible episodic respiratory obstruction due to bronchoconstriction and mucus that fill small and large airways
Pathologic findings in asthma
-Gross: overdistended lungs, mucus plugs
HISTOLOGY
-edema and inflammatory infiltrate with prominent EOSINOPHILS, also mast cells, lymphocytes, macrophages
-hypertrophy of submucosal glands
-hypertrophy and/or hyperplasia of smooth muscle
-thickening of basement membrane
What can be seen in expelled cough/sputum of asthma?
- Cruschmann spirals-plugs of shed respiratory epithelium, may form casts in airways
- Creola bodies: aggregates of columnar cells
- Charcot-Leyden crystals: from phospholipids in plasma membrane of eosinophils
Pathogenesis of asthma
ATOPIC
-linked to atopy and allergies: Type I hypersensitvity, childhood, family hx
-allergen induces Th2 lymphocytes, activate B cells that produce IgE
-IgE attaches to mast cells or basophils and with 2nd stimulus, release histamine and leukotriene B4
-leads to bronchoconstriction, mucus secretion, vasodilation, increased vascular permeability
NON ATOPIC
-Non-atopic: airway hyper-irritability
-occupational asthma
