What is the US prevalence of severe combined immunodeficiency (SCID)?

Updated: Aug 11, 2020
  • Author: Francisco J Hernandez-Ilizaliturri, MD; Chief Editor: Emmanuel C Besa, MD  more...
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The accurate incidence of SCID in the United States is unknown, but it has been estimated to be in 1 per 50,000-100,000 births across all ethnic groups. A postulated reason for the lack of exact epidemiologic information is that infants with SCID may die of infections without having been diagnosed with the condition.

With implementation of SCID newborn screening in unbiased populations, Kwan et al reported that 1 in 58,000 infants (95% CI 1/46,000–80,000) are born with SCID or leaky SCID (ie, forms of SCID, such as Omenn syndrome, characterized by normal or elevated levels of nonfunctional T cells, in contrast to the low or absent T cell counts of typical SCID). That prevalence rate is nearly twice the previous estimates based on population data or experience of centers performing hematopoietic cell transplantation therapy for SCID. [6]

The approximate frequency of the most common forms of SCID is as follows:

  • X-linked SCID -  42%
  • Autosomal recessive SCID - 22%
  • ADA deficiency - 15%
  • JAK3 deficiency - 6%

The incidence of reticular dysgenesis and CHH are less than 1% each. In approximately 14% of cases, the etiology remains unknown. [7]

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