The underlying cause of asthma is unknown, although airway inflammation is known to be a major component. The triad of airway inflammation, smooth muscle hyperreactivity, and reversible airway obstruction is characteristic for patients with asthma.

Numerous triggers can precipitate an asthma flare-up, including viral upper respiratory tract infections, sinus infections, exercise, exposure to cold air, weather changes, exposure to allergens (e.g., dust, cockroaches, animal dander, pollen, grass, mold, or certain foods such as shellfish or peanuts), exposure to strong odors (e.g., cigarette smoke, strong chemicals, perfumes), and emotional states (e.g., fear, laughing, crying).

Asthma symptoms are secondary to airway obstruction brought about by airway inflammation and mucus production and/or increased airway resistance from bronchospasm. Wheezing is the classic presentation of asthma, but other symptoms include chronic coughing (often referred to as cough-variant asthma), shortness of breath, and chest pain or tightness.

A detailed history and physical examination are integral to making the diagnosis of asthma. Wheezing, rhonchi, coarse or decreased breath sounds, or a prolonged expiratory phase may be noted on pulmonary examination. Lung sounds can also be entirely normal at the time of examination, even in patients with a significant history.

Spirometry with a bronchodilator response is used to assess for asthma. In patients with asthma, an obstructive pattern with post-bronchodilator improvement in lung function is frequently seen. If spirometry is not available, a handheld peak-flow meter can be substituted.

An autosomal recessive disorder, cystic fibrosis is the most common genetic disease affecting whites. The gene is located on chromosome number 7 and codes for a transmembrane protein (cystic fibrosis transmembrane conductance regulator (CFTR)-protein) that functions as a chloride channel. The most common abnormality is an amino acid defect consisting of the deletion of a phenylalanine (the delta F508 mutation).The disease is characterized by multiorgan involvement. Chronic sinopulmonary infections (facilitated by excess altered mucus production in the respiratory tract), pancreatic insufficiency, and abnormalities of the exocrine glands and reproductive tract are major manifestations. In the lungs, dry, thickened secretions hinder clearance of pulmonary secretions. Impaired airway clearance, in combination with abnormal colonization with organisms (e.g., Staphylococcus aureus, Pseudomonas aeruginosa), leads to the development of bronchiectasis and permanent lung damage.

Major symptoms include a chronic, productive cough, yellow-green sputum, chest congestion, hemoptysis, steatorrhea, poor weight gain, failure to thrive, and meconium ileus or meconium ileus equivalent (intestinal obstruction).

A detailed family history should be obtained as well as growth patterns and stool characteristics. Cardinal features noted on physical examination may include tachypnea, retractions, bronchial breath sounds, wheezes, crackles, a prolonged expiratory phase, nasal polyps, upper airway congestion, digital clubbing, reduced height and weight, rectal prolapse, and hepatomegaly and splenomegaly.

The following laboratory studies are indicated: