Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

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What is Cryptogenic fibrosing alveolitis?

Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis) is a disease of the lung.

The lungs are composed of air passages, starting from the trachea (or windpipe) which divides into a left and right main bronchus, which keep dividing until they become bronchioles, and finally terminating into alveoli. The alveoli are small folded membranes shaped like a cluster of grapes. They are the interface between the air and blood stream and that is where gas exchange takes place.

The function of the alveoli is dependent on the alveolar wall which is a thin membrane, allowing for oxygen and carbon dioxide to move freely across it.

CFA is a disease affecting both the walls and the interior of alveoli. It causes fibrosis of the alveolar walls, which impairs gas exchange. It is an idiopathic disease - meaning at this stage it is not known what causes it.

It is important to note that a lot of other diseases may cause lung fibrosis other than CFA - ie where a causative factor is known.

Who gets Cryptogenic fibrosing alveolitis?

This is the most common form of diseases of the category: "interstitial lung disease". It affects between 5-26 in every 100,000 individuals, usually between the ages of 40 - 60 years. The incidence of CFA is rising.

Predisposing Factors

Although a causative factor has not yet been found, it appears that genetic predisposition to the disease is important. There is also an association between CFA and exposure to wood and metal dust.

Other diseases which may cause lung fibrosis include:

Connective tissue diseases (e.g. rheumatoid arthritis, scleroderma, systemic lupus erythematosus)

Granulomatous diseases - Tuberculosis , sarcoid, extrinsic allergic alveolitis.

Other causes:

Drugs - e.g. amiodarone (anti-arrhythmic), methotrexate, d-penicillamine

Radiotherapy

Occupational diseases - coal, silica, asbestos;

Infections - e.g. influenza, acute pneumonitis due to other causes.

Progression

It is thought that the disease begins with inflammation of the alveoli. After a while, this inflammation in the walls and alveolar spaces is replaced by fibrous tissue. This fibrosis spreads progressively to include the whole lung, making it stiff, solid, and ineffective. The rate at which this process occurs is hard to predict: over many years for some people, whereas in others fibrosis may develop in a matter of weeks.

Over time complications such as pulmonary hypertension, cor pulmonale and respiratory failure set in.

The natural history of other causes of fibrosis may differ in the rate of progression and whether there is continual exposure to the causative factor - for example if the offending drug is stopped - the fibrosis will stop progressing.

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