What are the other Names for this Condition? (Also known as/Synonyms)

• Bare Lymphocyte Syndrome II (BLS II)
• SCID, HLA Class 2-Negative
• Severe Combined Immunodeficiency, HLA Class II-Negative

What is Bare Lymphocyte Syndrome Type 2? (Definition/Background Information)

• Bare Lymphocyte Syndrome Type 2 (BLS 2) is an inherited disorder of the immune system categorized as a form of combined immunodeficiency (CID). People with BLS 2 lack virtually all immune protection from bacteria, viruses, and fungi. They are prone to repeated and persistent infections that can be very serious or life-threatening
• Immunodeficiency by defective expression of HLA class 2 is a rare primary genetic immunodeficiency disorder characterized by partial or complete absence of human leukocyte antigen class 2 expression resulting in severe defect in both cellular and humoral immune response to antigens
• The disorder presents clinically as marked susceptibility to infections, severe malabsorption and failure to thrive and is often fatal in early childhood

(Source: Bare Lymphocyte Syndrome Type 2; US National Library of Medicine and Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

Who gets Bare Lymphocyte Syndrome Type 2? (Age and Sex Distribution)

• Bare Lymphocyte Syndrome Type 2 is a congenital disorder. The presentation of symptoms may occur following the birth of the child
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Bare Lymphocyte Syndrome Type 2? (Predisposing Factors)

• A positive family history may be an important risk factor, since Bare Lymphocyte Syndrome Type 2 can be inherited

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Bare Lymphocyte Syndrome Type 2? (Etiology)

• Bare Lymphocyte Syndrome Type 2 is a genetic disorder that is transmitted in an autosomal recessive manner

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Bare Lymphocyte Syndrome Type 2?

The signs and symptoms of Bare Lymphocyte Syndrome Type 2 may include:

• Agammaglobulinemia
• Biliary tract abnormality
• Chronic lymphocytic meningitis
• Chronic mucocutaneous candidiasis
• Colitis
• Cutaneous anergy
• Encephalitis
• Failure to thrive
• Malabsorption
• Neutropenia
• Panhypogammaglobulinemia
• Protracted diarrhea
• Recurrent bacterial infections
• Recurrent fungal infections
• Recurrent lower respiratory tract infections
• Recurrent protozoan infections
• Recurrent upper respiratory tract infections
• Recurrent urinary tract infections
• Recurrent viral infections
• Villous atrophy
• Viral hepatitis

(Source: Bare Lymphocyte Syndrome Type 2; Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

How is Bare Lymphocyte Syndrome Type 2 Diagnosed?

Bare Lymphocyte Syndrome 2 is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Bare Lymphocyte Syndrome Type 2?

The complications of Bare Lymphocyte Syndrome 2 may include:

• Severe and recurrent infections that are life-threatening
• Severe malnutrition

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Bare Lymphocyte Syndrome Type 2 Treated?

There is no cure for Bare Lymphocyte Syndrome 2, since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complications that develops.

How can Bare Lymphocyte Syndrome Type 2 be Prevented?

Currently, Bare Lymphocyte Syndrome 2 may not be preventable, since it is a genetic disorder.

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Bare Lymphocyte Syndrome Type 2? (Outcomes/Resolutions)

• The prognosis of Bare Lymphocyte Syndrome 2 is dependent upon the severity of the signs and symptoms and associated complications, if any
• Typically, the prognosis of BLS 2 is poor and many deaths are reported among young children

Additional and Relevant Useful Information for Bare Lymphocyte Syndrome Type 2:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/