MHC Class II Deficiency (Bare Lymphocyte Syndrome Type II)
A rare inherited disorder in which immune cells fail to display MHC class II molecules, leading to severe, recurrent infections and impaired antibody responses from early infancy.
- Combined Immunodeficiency
- Hematopoietic Stem Cell Transplant Access
- Specialist Immunology Review
- Typical Onset
- Infancy
- Inheritance Pattern
- Autosomal Recessive
- Key Genes
- CIITA, RFX5, RFXAP, RFXANK
- Definitive Treatment
- Allogeneic HSCT
Condition Overview
MHC Class II Deficiency, also called Bare Lymphocyte Syndrome Type II, is a rare inherited disorder of the immune system. Cells that should display human leukocyte antigen (HLA) class II molecules on their surface fail to do so because of mutations in genes that regulate class II gene expression, rather than in the HLA genes themselves.
Because class II molecules are essential for activating helper T cells and coordinating antibody production, affected infants typically develop severe, recurrent bacterial, viral, and fungal infections starting in the first months of life. Chronic diarrhea, failure to thrive, and respiratory infections are common presenting features.
Early recognition matters because this is a life-threatening combined immunodeficiency. Children who are diagnosed promptly and proceed to allogeneic hematopoietic stem cell transplantation have meaningfully better outcomes than those diagnosed late, after irreversible organ damage or infection-related complications have occurred.
Types and Subtypes
MHC Class II Deficiency is classified by which gene in the class II transactivation pathway is affected. All subtypes share the same clinical picture of absent HLA class II expression, though the genes themselves are unrelated in function.
Symptoms and Signs
Symptoms usually begin in the first year of life and reflect the combined cellular and antibody defects caused by absent MHC class II expression.
Causes and Risk Factors
MHC Class II Deficiency is caused by inherited mutations in genes required for transcription of HLA class II genes, not in the HLA genes themselves.
Diagnosis and Investigations
Diagnosis combines immune phenotyping with genetic confirmation.
Disease Severity and Risk Stratification
MHC Class II Deficiency does not use a tumor-style staging system. Instead, clinicians stratify risk based on infection burden, organ involvement, and timing of diagnosis relative to transplant.
Standard Treatment Options
Treatment centers on preventing infections while pursuing curative hematopoietic stem cell transplantation as early as possible.
Advanced & Emerging Therapies
Because the immune defect is intrinsic to bone marrow-derived cells, cellular replacement strategies remain the focus of advanced care for this condition.
Cellular Therapy
Allogeneic Hematopoietic Stem Cell Transplantation
The established curative approach, using matched related, unrelated, or haploidentical donors depending on availability.
Cellular Therapy
Reduced-Intensity Conditioning Protocols
Increasingly used to lower transplant-related toxicity in infants with pre-existing organ compromise.
Gene Therapy
Investigational Gene Correction Approaches
Early-phase research is exploring gene addition or correction strategies for select primary immunodeficiencies; not yet a standard option for this condition.
Biomarkers & Precision Medicine
Laboratory and genetic markers guide diagnosis, transplant planning, and monitoring of immune recovery.
When a Second Opinion May Be Important
Because outcomes are time-sensitive, specialist input early in the disease course can meaningfully change the treatment path.
Clinical Trials & Research
Prognosis & Outcome Factors
Outcomes in MHC Class II Deficiency depend heavily on how early the diagnosis is made and whether transplant occurs before significant infection-related organ damage develops.
Supportive Care and Living with MHC Class II Deficiency
Supportive care addresses infection prevention, nutrition, and family wellbeing throughout diagnosis and the transplant journey.
How CancerFax Helps You Explore Treatment Options
CancerFax helps families of children with MHC Class II Deficiency obtain specialist immunology report review, coordinate second opinions, and connect with hospitals experienced in pediatric hematopoietic stem cell transplantation, including cross-border care coordination where relevant.
Get a free case reviewFrequently Asked Questions
MHC Class II Deficiency, also called Bare Lymphocyte Syndrome Type II, is a rare inherited immunodeficiency in which immune cells cannot display HLA class II molecules, impairing the body's ability to fight infections and mount normal antibody responses.
It is caused by autosomal recessive mutations in genes (CIITA, RFX5, RFXAP, or RFXANK) that regulate the expression of HLA class II genes, rather than in the HLA genes themselves.
Diagnosis relies on flow cytometry showing absent or reduced HLA-DR expression on immune cells, followed by genetic testing to confirm the affected gene.
Allogeneic hematopoietic stem cell transplantation can be curative for the underlying immune defect, particularly when performed early before major infectious complications occur.
Recurrent infections, chronic diarrhea, and failure to thrive starting in the first months of life are the most common presenting features.
Yes, genetic testing can identify carrier or affected status in siblings, and HLA typing of siblings is important to evaluate donor options.
Alternative donor strategies, including haploidentical or unrelated donor transplants, may be considered with specialist guidance.
Immunoglobulin replacement and infection prophylaxis manage symptoms but do not correct the underlying immune defect; transplant remains the only curative option currently available.
MHC Class II Deficiency follows autosomal recessive inheritance, meaning both parents typically carry one copy of a mutated gene.
Yes. CancerFax can help coordinate review of your child's immunology and genetic reports, facilitate second opinions, and connect your family with hospitals experienced in pediatric stem cell transplantation, including support for cross-border treatment coordination.
Exploring Care Options for MHC Class II Deficiency?
Send your medical reports for specialist review and connect with centers experienced in primary immunodeficiency and inherited metabolic-inflammatory disease management.