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Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

human lung

What is Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

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.

Statistics on Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

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.

Risk Factors for Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

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 of Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

    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.

    How is Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis) Diagnosed?

     

  • Blood tests: Not very useful for diagnosis of CFA. The erythrocyte sedimentation rate (ESR) is slightly elevated. One third of patients are positive for rheumatoid factor and antinuclear factor, two markers commonly associated with autoimmune disease.
  • Arterial blood gas testing shows low blood oxygen, with normal carbon dioxide.
  • A chest x-ray is very useful in suggesting a diagnosis of CFA. Variable degress of fibrosis may be seen.

    Prognosis of Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis)

    CFA has a high morbidity and mortality with only about half of all patients surviving to 5 years; the acute form has a higher mortality. Lung transplantation is most successful in younger patients, with 50% 3 year survival. Lung fibrosis due to other causes has a variable prognosis.

    How is Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis) Treated?

    This is a difficult disease to treat effectively.

     

  • The most common therapy is with corticosteroids and immunosuppressives; however, these are only beneficial in about 25% of patients. The usual medications used are prednisolone (a corticosteroid) and azathioprine or cyclophosphamide (immunosuppressives). Either of these types of medication may cause significant side effects.

    Cryptogenic fibrosing alveolitis (Idiopathic pulmonary fibrosis) References

    [1] Cotran RS, Kumar V, Collins T. Robbins Pathological Basis of Disease Sixth Ed. WB Saunders Company 1999. pp735-36
    [2] Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 1998. pp813-15
    [3] Talley NJ, O’Connor S. A guide to physician examinations. Third Ed. MacClennan & Petty, 1996.

 

Dates

Posted On: 23 May, 2003
Modified On: 13 March, 2014

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