About PIDs

Primary Immunodeficiency Diseases (PID) represent a class of disorders in which there is an intrinsic genetic defect in the immune system. These unique “experiments of nature” continue to unravel novel molecular and cellular mechanisms that govern development and function of the human immune system. In the last two decades the field of PID has been expanded enormously. Many more syndromes have been described and more than 150 different genes with mutation causing immune-deficiencies have been discovered.These disorders, hitherto considered rare, are in fact believed to be rather common. However, the true incidence or population prevalence figures of these diseases, either individually or in the aggregate, are not known because there is no screening for these defects either at birth or at any time subsequently thereafter anywhere in the world.

Prevalence rates for diagnosed PIDs have been estimated to be 1 in 2,000 for children, 1 in 1,200 for all, and 1 in 600 households based on a population based survey in the United States.The total population estimate of diagnosed PIDs in the USA based on these prevalence rates would be between 1,50,000 to 3,60,000 individuals. Most of the prevalence data are derived from extrapolation of diagnosed cases based on patient based PID national registries from geographically localized areas of the world.The figures obtained from registry based data tend to largely underestimate the actual incidence and prevalence because of lack of clinical recognition, lack of reporting to the registries, overrepresentation of certain referral centres, lack of a standardized case definition, and death before recognition. As a result, neither the true incidence nor true prevalence of PID is exactly known. The number of undiagnosed cases is not known because there is no population-based screening process for PID anywhere in the world as there is no single laboratory test which can be utilized for screening of all PIDs. Population based surveys are virtually impossible to conduct for these group of disorders. Moreover, individuals with less severe forms of PID remain undiagnosed for a longer duration. It is estimated that there are more than 6 million patients with PID worldwide, with similar prevalence all over the globe in countries where PID registries are being maintained. Based on this, it is estimated that there could be more than one million patients with PID in India.

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