Pulmonary Fibrosis

 

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Definition

Pulmonary Fibrosis (PF) describes a condition in which the lung tissue becomes thickened, stiff, and scarred. The medical terminology used to describe this scar tissue is fibrosis. The alveoli and the blood vessels within the lungs are responsible for delivering oxygen to the body, including the brain, heart, and other organs. As lung tissue becomes scarred and thicker, it is more difficult for the lungs to transfer oxygen into the bloodstream. As a result, the brain, heart, and other organs do not get the oxygen they need to function properly. In some cases, doctors can determine the cause of the fibrosis, but in many cases the cause remains unknown. When there is no known cause for the development of pulmonary fibrosis (and certain radiographic and/or pathologic criteria are met), the disease is called idiopathic pulmonary fibrosis or IPF. More specifically, consensus treatment guidelines from international lung societies define IPF as “a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, occurring primarily in older adults, limited to the lungs, and associated with the histopathologic and/or radiologic pattern of UIP [usual interstitial pneumonia].

If there is a clear association with another illness or the lung fibrosis is the result of a side effect from a medication or an exposure to an agent known to cause PF, then the cause of the disease is no longer considered idiopathic. PF clearly associated with another disease, such as scleroderma or rheumatoid arthritis, would be referred to as pulmonary fibrosis secondary to scleroderma or secondary to rheumatoid arthritis.

Idiopathic pulmonary fibrosis portends a poor prognosis, with an estimated mean survival of 2-5 years from the time of diagnosis.Estimated mortality rates are 64.3 deaths per million in men and 58.4 deaths per million in women.

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Incidence and Prevalence

There are no reliable data to determine how many people are affected by PF, possibly due to the large number of conditions under which it can arise.

According to the ATS, the incidence of IPF was estimated at 10.7 cases per 100,000 per year for men and 7.4 cases per 100,000 per year for women in a population-based study from the county of Bernalillo, New Mexico. A study from the United Kingdom reported an overall incidence rate of only 4.6 per 100,000 person-years, but estimated that the incidence of IPF increased by 11% annually between 1991 and 2003. This increase was not felt to be attributable to the aging of the population or increased ascertainment of milder cases. A third study from the United States estimated the incidence of IPF to be between 6.8 and 16.3 per 100,000 persons using a large database of healthcare claims in a health plan.

Prevalence estimates for IPF have varied from 2 to 29 casesper 100,000 in the general population. The wide rangein these numbers is likely explained by the previous lack of uniform definition used in identifying cases of IPF, as well as by differences in study designs and populations. A recent analysis based on healthcare claims data of a large health plan in the United States yielded a prevalence estimate of between 14.0 and 42.7 per 100,000 persons depending on the case definition used. It is unknown if the incidence and prevalence of IPF are
influenced by geographic, ethnic, cultural, or racial factors.

Causes

• Idiopathic Disorders: Idiopathic Pulmonary Fibrosis(IPF), acute interstitial pneumonia(AIP), idiopathic non-specific interstitial pneumonia(NSIP), sarcoidosis.
• Connective tissue and Autoimmune disease: Sleroderma/Progressive systemic sclerosis, Lupus, Rheumatoid arthritis(RA), polyomyositis/dermatomyositis.
• Occupational and Environmental: Inorganic dust, organic dust, gases and fumes, radiation.
• Drug Induced: Chemotherapeutic agent, radiation therapy, antiarrythmics, antibiotics, anticonvulsants.
• Infections: Viral and bacterial.
• Genetic/Inherited: Familial pulmonary fibrosis, Hermansky-Pudlak syndrome.

Other factors associated with the disease is heavy smoking and acid reflux disease(GERD).

Diagnostic Procedures

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