Summary about Disease
Bare lymphocyte syndrome (BLS), also known as severe combined immunodeficiency (SCID) due to major histocompatibility complex (MHC) deficiency, is a rare genetic disorder characterized by the near or total absence of MHC class I or MHC class II molecules on the surface of cells. MHC molecules are crucial for presenting antigens to T lymphocytes, a key component of the adaptive immune system. Their absence leads to severe immune deficiency, making affected individuals highly susceptible to infections.
Symptoms
Symptoms of BLS are similar to those of other SCID disorders and typically manifest in early infancy. Common symptoms include:
Recurrent and persistent bacterial, viral, and fungal infections
Failure to thrive (poor growth and weight gain)
Chronic diarrhea
Skin rashes (eczema)
Pneumonia
Meningitis
Causes
BLS is caused by genetic mutations that disrupt the expression of MHC class I or MHC class II molecules. These mutations typically affect genes involved in the regulation of MHC gene transcription, like RFXANK, *RFX5*, *RFXAP*, *CIITA*, and *TAP1/2*. It is usually inherited in an autosomal recessive manner, meaning that both parents must carry the defective gene for a child to be affected.
Medicine Used
Treatment for BLS primarily aims to reconstitute the immune system and prevent or manage infections. Approaches include:
Hematopoietic stem cell transplantation (HSCT): This is the definitive treatment for BLS and involves replacing the patient's defective immune system with healthy stem cells from a donor.
Intravenous immunoglobulin (IVIG): Provides passive immunity by supplying antibodies to help fight infections.
Antibiotics, antivirals, and antifungals: Used to treat and prevent specific infections.
Prophylactic antibiotics/antivirals/antifungals: Preventative medications to reduce the likelihood of opportunistic infections.
Is Communicable
BLS itself is not communicable. It is a genetic disorder, not an infectious disease. However, individuals with BLS are highly susceptible to communicable diseases due to their compromised immune system.
Precautions
Due to their severe immunodeficiency, individuals with BLS require strict precautions to minimize exposure to pathogens:
Isolation: Limiting contact with people who are sick.
Hygiene: Meticulous handwashing and environmental hygiene.
Avoidance of live vaccines: Live vaccines can cause serious infections in immunocompromised individuals.
Prophylactic medications: As mentioned previously.
Cooked Food and Clean Water: Avoid raw or undercooked foods, especially meats. Using boiled or tested bottled water.
How long does an outbreak last?
BLS is a chronic condition, not an outbreak. Individuals with BLS have a persistent immune deficiency throughout their lives unless successfully treated with HSCT. The duration of infections in BLS patients can vary widely depending on the specific pathogen, the severity of the immune deficiency, and the effectiveness of treatment.
How is it diagnosed?
Diagnosis of BLS typically involves:
Clinical evaluation: Assessing the patient's medical history, symptoms, and physical examination findings.
Immunological testing:
Flow cytometry to assess the expression of MHC class I and MHC class II molecules on immune cells. Reduced or absent expression is a key diagnostic feature.
Complete blood count (CBC) and lymphocyte subset analysis to evaluate the number and function of different immune cells.
Antibody level assessment to see if patient has had success with fighting off previous diseases.
Genetic testing: To identify the specific genetic mutation responsible for the disease.
Timeline of Symptoms
Early infancy (0-6 months): Onset of recurrent infections, failure to thrive, chronic diarrhea, and skin rashes.
Infancy and childhood: Continued susceptibility to infections, potentially leading to severe complications such as pneumonia, meningitis, and sepsis.
Without treatment: Progressive immune deficiency and increased risk of life-threatening infections.
Important Considerations
Early diagnosis and intervention are crucial to improve outcomes for individuals with BLS.
HSCT offers the best chance for long-term survival and immune reconstitution.
Genetic counseling is important for families with a history of BLS to understand the risk of recurrence in future pregnancies.
Management of infections is a critical component of care, even after HSCT, as immune reconstitution may take time.
Psychosocial support is essential for patients and families coping with the challenges of this chronic and life-threatening condition.