Severe Combined Immunodeficiency(SCID) is a very rare genetic disorder, which causes problems with the baby’s immune system.
If left untreated, babies with SCID can experience poor growth, chronic diarrhea, a yeast infection called thrush, skin rashes, and life-threatening infections. SCID can be detected soon after birth with newborn screening , allowing for prompt treatment.
Here is more complete information about the definition, symptoms, causes, risk factors, and how to treat it.
SCID is Severe Combined Immunodeficiency, a Rare Disease That Affects Babies
SCID is a primary inherited immunodeficiency disease (PIDD) that usually appears in infancy. It causes a severe immunodeficiency that weakens the immune system so that it is unable to fight off even minor infections. It is considered the most serious PIDD.
This rare condition is caused by a genetic defect that affects the function of T cells. Depending on the type of SCID, B cells and NK cells may also be affected. These cells play a vital role in helping the immune system fight off bacteria, viruses, and fungi that cause infections.
Affected infants are at risk of dying within the first year of life without treatment with hematopoietic stem cell transplantation. HSCT or newborn screening for SCID can identify infants before they become ill, resulting in earlier transplantation times and better outcomes after transplantation. Transplantation within the first 3 months of life provides the best chance for a successful outcome.
There are several forms of SCID. The most common type is related to a problem with a gene on the X chromosome, which only affects males. Females can carry the condition, but they also inherit a normal X chromosome.
Since the initiation of SCID screening in newborns, recessive forms of the disease that can affect both boys and girls have been identified with increasing frequency.
Other forms of SCID are caused by a deficiency of the enzyme adenosine deaminase (ADA) and various other genetic defects.
How Can SCID Affect a Baby’s Immunity?
In a developing baby, the immune system begins in the bone marrow. Stem cells there can become one of three different types of blood cells:
- Red blood cells
- White blood cells
- Platelets
White blood cells protect the body from infections and foreign invaders. There are different types of white blood cells, including lymphocytes (lim-FOE-sites). Lymphocytes come in two main types: B cells and T cells. These cells are key to fighting infections:
- T cells identify, attack, and kill “invaders.”
- B cells make antibodies that “remember” the infection and are ready if the body is exposed again.
SCID is a “combined” immunodeficiency because it affects both of these infection-fighting white blood cells.
In SCID, the child’s body has too few lymphocytes or lymphocytes that do not function properly.
Because the immune system isn’t working as it should, it may be difficult or impossible to fight off the germs — viruses, bacteria, and fungi — that cause infections.
Symptom
In addition to frequent and sometimes very severe respiratory infections, other symptoms of SCID in infants include poor growth, a rash that looks like eczema, chronic diarrhea and recurrent thrush in the mouth, although all of these symptoms may not be present.
Often, SCID is associated with recurrent viral infections and results in multiple hospitalizations before the cause is found.
One unusual infection that can be present with SCID early on is pneumocystis pneumonia. The presence of this infection is a red flag, making it essential to evaluate the immune system for SCID.
Babies with SCID may appear healthy at birth, but problems can arise soon afterward, such as:
- Failure to thrive
- Chronic diarrhea
- Frequent serious respiratory infections
- Oral thrush (a type of fungal infection in the mouth)
- Other bacterial, viral, or fungal infections that can be serious and difficult to treat, such as: Ear infections (acute otitis media), sinus infections ( sinusitis ), skin rashes, meningitis, pneumonia .
Reason
SCID is an inherited condition, meaning it runs in families in the same way that physical characteristics, such as eye color, are passed from parent to child. It is caused by an error (or mutation) in the child’s genetic makeup.
In babies with SCID, genetic errors result in the absence or malfunction of proteins necessary for normal development and/or function of the immune system.
Many different genes can be affected, and each causes a different type of SCID. Recent advances in genetics mean that doctors can now often make a specific diagnosis of SCID.
The names given to the different types of SCID are based on the specific proteins or genes that are affected. Some of the more common types include common gamma chain deficiency, adenosine deaminase (ADA) deficiency, JAK 3 kinase deficiency, MHC class II deficiency, and recombinase activating gene (RAG) deficiency.
Although the management and treatment of babies with SCID are usually very similar for all types, it is important to know the exact cause. Because in some conditions there may be specific treatments available, and to allow for accurate genetic counseling for babies with SCID. future pregnancies.
Frequency of Occurrence
X-linked SCID is the most common form of a group of severe combined immunodeficiency disorders. This group of disorders can be caused by variants in more than 20 genes.
The incidence of all severe combined immunodeficiency disorders is 1 in 60,000 newborns and it is estimated that one-quarter to one-third of these cases are X-linked SCID.
Risk Factors
SCID is very rare. It affects up to 1 in every 100,000 babies born in the United States. It also tends to be more common in people of Apache, Navajo, and Turkish backgrounds.
Because this condition is genetic, the risk factor is greater if both parents inherit the gene for SCID. The condition is inherited in an X-linked recessive pattern.
The gene associated with this condition is located on the X chromosome, which is one of two sex chromosomes. In males (who have only one X chromosome), one copy of the altered gene in each cell is enough to cause the condition.
In females (who have two X chromosomes), the variant must occur in both copies of the gene to cause the disorder. Because it is unlikely that a female will have two copies of the altered gene, males are more likely to be affected by X-linked recessive disorders than females.
The characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
Diagnosis
Doctors use a simple blood test to identify newborns who may have health problems, such as sickle cell disease and cystic fibrosis . The conditions screened for vary by state, but all now offer screening for SCID.
Newborn screening for SCID allows for early diagnosis, and prompt treatment results in better outcomes.
Babies with tests that suggest SCID are usually referred to a doctor who specializes in immune deficiencies. The doctor will do other blood tests and possibly genetic testing.
Parents who have a child with SCID or a family history of immunodeficiency may want to consider genetic counseling and blood testing as early as possible. Early diagnosis can lead to faster treatment and better outcomes. It may also be possible to test high-risk infants for the disease before birth if the genetic mutation that causes SCID is known in the family.
Children without a known family history of the disease or who do not have newborn screening are often not diagnosed until 6 months of age or later.
Some other examinations are:
- Routine neonatal screening using the T cell receptor excision circle (TREC) test
- History of persistent infection
- White blood cell count (WBC)
- Mitogen antigen stimulation test and vaccine
Screening of all neonates using the TREC test is often recommended and performed routinely.
Handling
The only cure currently and routinely available for SCID is a bone marrow (stem cell) transplant, which provides the patient with a new immune system.
The most successful stem cell transplants use cells donated by a sibling. Sometimes, a parent’s stem cells are also a match.
If no family member is a suitable donor, doctors may use stem cells from an unrelated donor. Some children with SCID may need chemotherapy before their transplant.
Babies with SCID who receive a stem cell transplant in the first few months of life, before they are exposed to infection, are more likely to survive.
Gene therapy as a treatment for some types of SCID has shown promise in clinical trials, but it has some risks and is not widely used. Research into gene therapy for SCID is ongoing.
Research into gene therapy for SCID continues and may one day be an option. If you think your child may have SCID, prompt evaluation by an immunologist is essential for early treatment.
Other forms of combined immunodeficiency may occur that may not require bone marrow transplantation.
It is important to remember that SCID is a pediatric emergency. Without immediate treatment, babies are unlikely to survive past their first year of life.
Children with SCID are usually treated by a medical team of several specialists, such as:
- Pediatric immunologist
- Bone marrow transplant doctor
- Pediatric infectious disease expert
Because children with SCID are at risk for life-threatening infections, they often begin medications to help prevent infections. Some may need regular infusions to replace antibodies.
Possible Complications
Babies with SCID may get sick easily from germs that don’t normally affect people with functional immune systems.
They may not respond to antibiotic treatment and may also deal with recurrent illnesses or infections that do not go away even with treatment. As a result, the most serious complication of SCID is death from severe infections.
Other complications may include:
- A life-threatening, infectious disease caused by bacteria, viruses, fungi, and parasites.
- Multiorgan failure
- Endocrinopathy
- Opportunistic violence
- Septic shock
- Congenital defects
- Respiratory insufficiency
- Anaphylactic shock
- Bleeding disorders
- Heart failure
- Acute and chronic kidney failure
- premature death
- Metabolic disorders (eg acidosis and alkalosis)
- Neurological complications include seizures and coma.
Prevention
This condition is not completely preventable, as it is passed from parents to children. Children with SCID should consider talking to a genetic counselor. A counselor can talk to you about genetic testing and planning a pregnancy.
However, if your child is diagnosed with SCID, in addition to medications and therapies to help prevent infections, other preventive measures are used. Children with SCID are:
- Isolating your little one to help prevent the spread of infection
- Should not receive live vaccines. Introducing viruses or bacteria to a child with SCID, even in weakened vaccine form, can be dangerous. This includes rotavirus vaccine, chickenpox (varicella) vaccine, measles, mumps, and rubella (MMR) vaccine, oral polio vaccine, BCG, and FluMist. Anyone living in the same household as the baby should also not receive any live vaccines.
- Children who need blood transfusions should receive blood that has been specially treated to help prevent transfusion-related complications.
- Breastfeeding may also be stopped until the breast milk is checked for viruses that can cause infection.
***
That’s the explanation about SCID condition which is a rare condition in babies. Hopefully this information is useful for Parents !
Republished with permission from theAsianparent Indonesia
