Clinical Features

CF is a multisystem disease, affecting a number of different organs and tissues throughout the body. Most of these manifestations have in common the production of abnormally viscous secretions from glands and surface epithelial cells. In the lung the mucus secretions from the bronchial epithelial cells are unusually thick. They are difficult to clear properly from the epithelial cells one of four tissue types found in the body, characterized by thin sheets and usually serving a protective or secretory function

Normal

No synthesis

Faulty processing; protein degraded (AF508)

Reduced synthesis membrane

Faulty processing; protein degraded (AF508)

membrane

There are three types of defects in CFTR production that can cause cystic fibrosis. The most common mutation, 4F508, causes faulty protein processing and degradation of the protein before it reaches the cell membrane. Other defects are also possible.

airway passages and, instead, tend to collect and obstruct the bronchial tree, while providing a perfect culture medium for dangerous bacteria. Over time, repeated bacterial infections damage and destroy the lung tissue, leading to chronic breathing problems and, eventually, to the loss of viable lung function. Indeed, the pulmonary manifestations of the disease are the main cause of death in most CF patients.

Obstruction in other organs is also seen. In the pancreas it leads to an insufficiency of pancreatic enzymes and malabsorption during digestion; in the nose and sinuses, it produces chronic sinusitis; and in the intestines, in a small minority of newborn infants with CF, it produces an often fatal condition called meconium ileus. Altered secretions also occur in the sweat glands, so that the sweat of CF patients has an abnormally high salt content. In fact, in the early days of medicine, the diagnosis of CF was often made by licking the skin and tasting the sweat! One additional mysterious clinical feature of CF occurs only in men with the disorder: They are infertile due to blockage or congenital absence of the vas deferens, the tube through which sperm pass prior to ejaculation.

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