Definition 
Bronchial asthma is a condition of the lungs which is characterized by

• periodic
• reversible broncho-constriction

Bronchi are hyperreactive to a variety of stimuli to which the patient is exposed intermittently.

Pathology
Bronchial lumen

• Bronchi and bronchioles contain thick, tenacious mucous plugs.

Cytologic examination of sputum after an asthmatic attack shows

• Eosinophils
• Charcot-Leyden crystals (orange, elongated, rhomboid crystals formed by degranulation of eosinophils) and
• Curshmann's spirals (dark staining core surrounded by lighter mucous).

Characteristic histologic findings of bronchial wall which lead to narrowing of the bronchus include:

• Thickening of the basement membrane
• Submucosal edema
• Hypertrophy of the submucosal glands and
• Hypertrophy of the smooth muscle cells.

Autopsy: Biopsy is rarely done. In patients dying of status asthmatics the lungs are over-expanded and small airways are occluded by mucoid secretions. There is a variable amount of bronchiolar inflammation, including eosinophilic infiltrates. Mucus glands are hyperplastic with hyperplasia of bronchial and bronchiolar smooth muscle

Pathogenesis

• Extrinsic or atopic asthma:
  • This group is an example of type I IgE-mediated hypersensitivity reaction to foreign antigens.
  • Begins in childhood.
  • The child (his or her respiratory tract mast cells) is sensitized to a substance which is extrinsic to the body.
  • A series of chemical and structural changes occur in the bronchi with exposure to the foreign substance.
  • Clinical examples: pollen, food, animal dander.
• Intrinsic or non-atopic:
  • This group is an example of a non-immune reaction causing asthma.
  • Clinical examples: aspirin, virus, stress, exercise.

Pathophysiology

Acute attack of dyspnea, prolonged coughing producing a large quantity of mucous, expiratory wheezing.