However, it can occur spontaneously in other words, it can occur without the mother being a carrier.Ī male with X-linked SCID will pass the gene along to his daughters, who will be carriers. This means that much of the time, the disease is passed from mother to son. X-linked SCID is called X-linked SCID because the mutation of the gene is on the X chromosome. X-linked SCID is characterized by very low T cells and non-functional B cells. Without these cells, the child with SCID will contract an infection quickly. The IL2RG gene tells the cells to make proteins that help immune cells to grow. X-linked SCID is caused by mutations in the IL2RG gene. Girls can be carriers of X-linked SCID but they won’t be affected. X-linked SCID generally only affects boys. Of all SCID cases, about 40% are X-linked.
X-linked SCID is the most common form of SCID. In autosomal recessive SCID, the child has two incorrect copies of the particular gene in each cell.īelow is a list of all of the types of SCID, with the top four most common ones discussed first, and the remaining listed in alphabetical order X-linked SCID These forms of SCID can affect boys and girls. X-linked SCID is caused by mutations on the X chromosome, and generally only occurs in boys.Īll of the other types of SCID are so-called autosomal recessive forms of SCID, meaning the mutations are on the other chromosomes. The most common types of typical SCID are: X-linked SCID, ADA SCID, RAG-1 or RAG-2 SCID, and IL7R SCID. The treatment approach will vary with the SCID types so it’s important to know what kind of SCID is affecting the child. Omenn Syndrome is characterized by defects in genes that cause high numbers of non-working T cells, and a lack of B cells resulting in a faulty immune system. Leaky SCID occurs when the defect in a gene allows for a normal, or even elevated, T cell count, which harms the immune system. The exceptions to typical SCID are leaky SCID and Omenn Syndrome. Most types of SCID are considered typical SCID, characterized by low or no T cells and a non-functional immune system.
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