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Lung-nontumor

Chronic obstructive pulmonary disease (COPD)

Asthma


Reviewers: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 30 January 2012, last major update August 2011
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Definition
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● Defined by the National Asthma Education and Prevention Program as a “chronic inflammatory disorder of the airways in which many cells and cellular elements play a role - in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophils and epithelial cells
● In susceptible individuals, causes episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or early morning
● Episodes are usually associated with widespread but variable airflow obstruction that is often reversible, either spontaneously or with treatment
● Inflammation also causes an associated increase in the existing bronchial hyperresponsiveness to a variety of stimuli
● Very common, affects 14-15 million Americans
● Causes 3,000 US deaths annually (American Academy of Allergy, Asthma & Immunology)
● Has increased in Western hemisphere over past 40 years

Clinical features
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Atopic or Extrinsic: Type I hypersensitivity, generally due to allergens; begins in childhood, triggered by environmental allergens (dander, dust, pollen, food), often positive family history; more common in African American children; evidence of allergen sensitization; skin test causes wheel and flare reaction (CMAJ 2009;181:E181)
Noneosinophilic (“neutrophilic”) asthma; a subgroup of atopic asthma not associated with eosinophilia; IL8 recruiting neutrophils are an important mechanism; patients tend to be less responsive to corticosteroids (Thorax 2011 Jul 23 [Epub ahead of print])
Nonatopic or Intrinsic: non-immune; due to aspirin ingestion, pneumonia, cold, stress, exercise; follows respiratory infection (rhinovirus, parainfluenza virus); usually not familial; no evidence of allergen sensitization; normal serum IgE, negative skin tests; viral induced inflammation may lower threshold of subepithelial vagal receptors to irritants
Occupational asthma: due to repeated exposure to fumes, dusts, gases, chemicals, often in minute quantities; varying mechanisms of disease depending upon the stimulus
Drug induced asthma: associated with several drugs, but most noteworthy is aspirin use; rare, aspirin related cases are associated with recurrent rhinitis, nasal polyps and urticaria; patients are sensitive to small doses of aspirin; may be due to direct effects of aspirin on cyclooxygenase pathway
Status asthmaticus: unremitting attacks due to exposure to previously sensitized antigen; may be fatal, usually in patients with a long history of asthma

Pathophysiology
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Atopic or Extrinsic: initial sensitization affects T helper 2 cells, which release IL4/5, which promote IgE release by B cells, mast cells, and eosinophils
● Re-exposure to allergen leads to mediator release from mucosal mast cells
● Acute/intermediate response is bronchoconstriction, edema, mucus secretion and vasodilation with increased vascular permeability
● Late phase reaction is due to influx of other inflammatory cells stimulated by chemokines released by mast cells, epithelial cells, T lymphocytes and other cytokines; includes release of major basic protein from eosinophils, which causes epithelial damage and airway constriction
● Putative mediators are leukotrienes C4, D4, E4 and acetylcholine; minor mediators are histamine, prostaglandin D2; associated with serum eosinophilia, sputum eosinophils

Gross description
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● Overdistended lungs, small areas of atelectasis, thick mucus plugs in proximal bronchi containing whorls of shed epithelium

Gross images
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Mucus plugs


Thickened bronchial walls

       
Status asthmaticus

Micro description
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● Curschmann spirals, eosinophils, extracellular Charcot-Leyden crystals (crystalloids composed of galectin-10, an eosinophil lysophopholipase), increased mucosal goblet cells and submucosal glands, thickened basement membrane, bronchial smooth muscle hypertrophy, airway wall edema

Micro images
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Smooth muscle hypertrophy and inflammatory cells


Goblet cells and inflammatory cells


   
Eosinophils and Charcot-Leyden crystals


           
Curschmann spirals

Virtual slides
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Asthma

Differential Diagnosis
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Allergic bronchopulmonary aspergillosis: important complication of asthma and cystic fibrosis
● Bronchocentric granulomatosis without the granulomatous inflammation

Additional references
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Dail and Hammar’s Pulmonary Pathology, 3rd edition

End of Lung-nontumor > Chronic obstructive pulmonary disease (COPD) > Asthma


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