Severe Combined Immunodeficiency or SCID also known as Swiss-type agammaglobulinemia is one of the rarest children diseases caused by deformities in any of several possible genes present in the human body. Characterized by the disturbed progress of functional T cells and B cells caused by numerous genetic mutations, this chronic ailment makes the affected one (mostly children) to have a very weak immune system which increases vulnerability to all the possible life-threatening infections.

Though it is considered a rare disease, over the past several decades it has been extensively studied since it provides a detailed insight and complexities of the human body’s immune system. Generally, most kids develop this kind of infection within the very first quarter of their lives. The affected child or infant is unable to fight off even the mildest of infections as the weakened immune system is unable to defend the body against dreadful bacteria, viruses and fungi.
Severe Combined Immunodeficiency

What Causes SCID?

While many genetic problems can cause SCID, primarily it is an inherited disorder. The most common type of SCID is X-linked severe combined immunodeficiency (SCID) that occurs almost exclusively in males. The gene that encodes the common gamma chain in these interleukin receptors is mutated in X-SCID. The mutation leads to an absence or abnormal functioning. Another form of SCID is caused by a deficiency of the enzyme adenosine deaminase (ADA), normally produced by a gene on chromosome 20.

Also read: Stem Cell Transplant: Learn How It Can Usher A New Lease Of Life

Symptoms Of SCID

Symptoms of SCID usually begin to show up within the first year of a child’s life. The most common symptoms of SCID that are most likely to occur are:

  • Frequent cases of pneumonia attacks
  • Repeated ear infections
  • Chronic liver infection
  • Failure to gain weight
  • Infections that require intravenous antibiotic treatment
  • A family history of immune deficiency
  • Meningitis
  • Diarrhea
  • Chronic skin infections


Early identification of SCID can make life-saving intervention possible before infections start to impact the major organs of the body, hence timely diagnosis of this life-threatening ailment is extremely important. It can be done in the following way: 

  • Routine neonatal screening using the T-cell receptor excision circle known as the TREC test is done. 
  • History of persistent infections is studied. 
  • An extremely low white blood cell count is constantly monitored. 
  • Mitogen and vaccine antigen stimulation assays are conducted. 


While the treatment for SCID can begin from treating the current infection and fixing the immune system by regular infusion to replace antibodies, the most effective treatment is bone marrow transplant. Transplantation of blood-forming stem cells from the bone marrow of a healthy individual helps the child’s immune system work better since bone marrow stem cells can live for a long time by renewing themselves and can produce a continuous supply of healthy immune cells. A bone marrow transplant from a tissue-matched sibling stands the best chances for curing SCID. However, most patients are not lucky enough to have a matched sibling donor, so transplants from unrelated, matched donors are usually performed. These transplants are less successful than transplants from a matched, related donor. Usually, a bone marrow transplant works well if it is done during a child’s first 3 months of life. Over the last few years, in some cases gene therapy treatment without a matched sibling donor for certain types of SCID has shown promising results.