What is SCID?

What is SCID?

Severe Combined Immune Deficiency (SCID) is the most severe form of Primary Immune Deficiency disease also called an inborn error of immunity. It is an inherited genetic disorder characterized by the absence of T cells, leading to a lack of B cell function. 

Children with SCID are highly vulnerable to life-threatening infections. Without treatment, they often succumb to opportunistic infections before reaching their first or second birthday. Additionally, live vaccines, which contain weakened viruses or bacteria, pose a significant risk to children with SCID. While these vaccines are generally safe for children with healthy immune systems, they can trigger severe, even fatal, infections in those with SCID.

SCID encompasses several genetic variants, which can affect both boys and girls. New variants continue to be identified. The most common form is X-Linked SCID (XSCID), which only affects boys. A well-known case in 1971 involved a boy born with XSCID who was placed in a sterile “bubble” by his doctors, as no alternative treatment was available at that time. This protective environment led to him becoming known as the “Bubble Boy,” and SCID became widely recognized as “Bubble Boy Disease.”

Prior to widespread newborn screening, SCID was estimated to affect approximately 1 in 100,000 births in the United States. However, as newborn screening programs became more prevalent and are now available across all 50 states and territories, the true incidence of SCID has been revealed to be higher than initially believed. Current estimates suggest that SCID occurs in roughly 1 out of 58,000 newborns.

The implementation of SCID newborn screening in the United States has led to earlier diagnosis for most infants, significantly increasing survival rates. Advancements in treatments, such as hematopoietic stem cell transplantation (HSCT), have also significantly improved the survival rates for SCID. As a result, more families now seek information and support for managing SCID. The SCID Foundation serves as a trusted resource, providing current information and support to families.