The immune system is impacted by a set of hereditary diseases known as severe combined immunodeficiency (SCID). These heredeitary diseases are caused by a gene mutation that exists at birth. Due to a malfunctioning immune system, SCID children are more likely to get major illnesses and infections.
SCID was nearly invariably fatal until recently. Early childhood infections that occurred often and repeatedly usually resulted in the death of SCID children. When a child had already developed a major illness and was around 6 months old, it was typical for SCID to go undetected. Now, children with SCID have successfully been treated thanks to neonatal screening, early interventions, and therapy improvements.
The true prevalence of severe combined immunodeficiency is unknown, though primary immunodeficiency disorders are quite common.
Because their antibodies from their biological parents still protect them, infants with SCID may not exhibit symptoms immediately. A child usually develops symptoms between the ages of three and six months.
SCID’s most noticeable symptoms include frequent or recurrent infections that result in chronic diarrhoea or pneumonia. Additionally, yeast infections and fungal pneumonia (caused by Pneumocystis jirovecii) are also common.
Additional symptoms include:
Inherited mutations are among the primary reasons for SCID materializing in over a dozen different genes. This indicates that one or both birth parents pass the disease on to the child.
Typically, SCID is a recessive characteristic. You probably won’t have SCID if the gene mutation exists in one copy of the gene. You will, however, carry the mutation and be able to pass it on to your offspring.
SCID is hereditary. It may result from many genetic disorders. The disorder can be inherited either as an X-linked trait or as an autosomal recessive trait:
Recessive genetic traits: When both parents have the trait, and the child inherits two copies of the trait, the traits are passed on. A person who carries the genetic trait for a disorder or condition but does not have it will typically be a carrier. A child with the disease has a 25% probability of being born to two carriers.
X-linked conditions: These illnesses are more prevalent in men and are X-chromosome-inherited. Because women often only carry the characteristic on one X chromosome, they are considered unaffected carriers.
SCID has no environmental risk factors.
It is crucial to identify SCID as soon as possible. SCID can be successfully treated in the first few months of life with a very high success rate. Blood lymphocyte levels can be determined via screening tests. An early SCID diagnosis is possible and particularly useful in case of a family history of immunodeficiency disorders.
T-cell counts are evaluated in dried blood samples obtained from heel pricks during screening. The test specifically assesses TRECs (T cell receptor excision circles). A low TREC result on this test indicates that the blood’s lymphocytes, a white blood cell, are not circulating in large quantities.
A healthcare provider may perform additional tests to confirm a positive result. Which subtypes of white blood cells are impacted can be determined by additional tests.