Today, we are seeing a very young patient who is having chronic difficulty in breathing. Since the patient is in great distress, we will try to make a rapid diagnosis.

• Our first guess is that the patient has asthma. This disease has three main features: 1) inflammation of the airway wall, 2) obstruction of the lumen of the airways by mucus, and 3) vasodilation of the bronchial blood vessels, causing increased vascular permeability and edema - water buildup. The inhaled allergen binds to IgE immunoglobulin on Mast cells that then release histamines, leucotrienes and other chemicals. The drug Singular blocks leukotriene receptors instead of blocking the histamine pathway as some older drugs do. (Diagram of bronchial asthma). Eosinophils, a type of white blood cell, are stimulated to release enzymes, including peroxidase, RNAse, DNAse, and lipases. Eosinophils normally help fight viral infections and parasites. In asthma, the inhaled allergen appears as a foreign invader and the eosinophils are recruited to fight the invasion. Alas, our patient doesn't seem to have asthma and we must look further ....

• Perhaps our patient is suffering from emphysema. Our young patient is unlikely to be a long-term smoker. But, suppose we do have a smoker as a patient or the patient has been subject to some long term insult to the lung - working in a factory or a printing shop, for example. Smoking and other chronic insult to the lung increases the number of macrophages, phagocytotic, amoeba-like cells, perhaps in the alveoli or the bronchi. The macrophages respond by secreting chemoattractants for neutrophils. Neutrophils accumulate and release elastase. Elastase is an enzyme that breaks down the elastic fibers surrounding the alveoli and other parts of the lung. Another enzyme, called antitrypsin, breaks down the elastase and prevents it from destroying the alveolar wall. If the smoking persists, the antitrypsin is no longer produced in sufficient concentrations, levels of antitrypsin decrease, and tissue wall destruction follows. (Diagram of emphysema). Fortunately, our patient doesn't have emphysema.

• The extreme youth of our patient, who turns out to be a baby, gives a clue - Epithelial cells lining the airways have CFTR ion pumps that use ATP to pump chloride out of the cells. Water flows out by osmosis, into the mucus secreted on the outside of the cells. Individuals with cystic fibrosis don't have working CFTR pumps. So, water no longer can follow the chloride movement, the mucus thickens and trapped bacteria lead to destruction of the epithelial cells. (Diagram of cystic fibrosis). Unfortunately, this is a difficult condition to treat as it is a genetic disease. One of the most promising treatment options may involve gene therapy.

Some of the material in this lecture follows the treatment of "Histology and Cell Biology" by Abraham L. Kierszenbaum (Mosby Press). I recommend it

All text and images, not attributed to others, including course examinations and sample questions, are Copyright, 2006, Thomas J. Herbert and may not be used for any commercial purpose without the express written permission of Thomas J. Herbert.