MHC class II deficiency

MHC (Major Histocompatibility Complex) class II deficiency, also known as bare lymphocyte syndrome type II (BLS II), is a rare autosomal recessive primary immunodeficiency disorder.

Characteristics:

• The disorder is characterized by the loss of expression of MHC class II antigens (HLA-DR, HLA-DQ, and HLA-DP) on antigen-presenting cells (APCs) [10].
• This results in impaired antigen presentation to T-cells, leading to a combined immunodeficiency syndrome [9].
• The lack of MHC class II expression leads to impaired function of dendritic cells, macrophages, and B cells [8].

Clinical Features:

• Typical manifestations include respiratory and gastrointestinal tract infections, septicemia, and recurrent infections during the first year of life [14].
• Developmental delays and failure to thrive may also occur [12].
• The disorder is often diagnosed in late childhood or early adulthood, although it can be present from birth [2].

Genetic Heterogeneity:

• MHC class II deficiency shows genetic heterogeneity, with multiple genes involved in the regulation of MHC class II expression [11].
• Defects in transacting regulatory factors required for expression of MHC class II genes are responsible for the disease phenotype [7][11].

Prevalence:

• The disorder is extremely rare, with only approximately 200 cases reported to date [15].

Overall, MHC class II deficiency is a severe combined immunodeficiency syndrome that requires prompt medical attention and treatment.

MHC class II deficiency, also known as bare lymphocyte syndrome type II (BLS II), is a rare autosomal recessive primary immunodeficiency characterized by the absence or strong reduction of MHC class II (HLA-DR, DP, DQ) expression on peripheral blood cells. The major clinical manifestations of this condition typically present themselves during the first year of life.

Common Signs and Symptoms:

• Recurrent Infections: Affected individuals often experience recurrent infections in various parts of their body, including:
  • Respiratory tract (e.g., pneumonia)
  • Gastrointestinal tract (e.g., diarrhea)
  • Urinary tract
• Septicemia: A life-threatening condition caused by bacteria in the blood.
• Failure to Thrive: Children with MHC class II deficiency may experience failure to gain weight and grow at a normal rate.
• Chronic Diarrhea: Persistent diarrhea is another common symptom of this condition.
• Pulmonary Infections: Recurrent lung infections are also characteristic of MHC class II deficiency.

Other Possible Symptoms:

• Neurological Symptoms: Some individuals may experience neurological symptoms, such as seizures or developmental delays.
• Autoimmune Features: Autoimmune cytopenia (a condition where the immune system attacks and destroys healthy blood cells) can occur in some cases.
• Allergies: Allergic reactions to certain substances may also be present.

Important Note:

MHC class II deficiency is a rare and serious condition that requires prompt medical attention. If you suspect that you or your child has this condition, it's essential to consult with a qualified healthcare professional for proper diagnosis and treatment.

References:

• [12] Major histocompatibility complex (MHC) class II deficiency is a genetic disease of autosomal recessive inheritance that is defined by absence or strong reduction of MHC class II (HLA-DR, DP, DQ) expression on peripheral blood cells.
• [13] MHC class II deficiency (MHC2D), also known as bare lymphocyte syndrome type II (BLS type II), is a rare autosomal recessive primary immunodeficiency showing genetic heterogeneity.
• [11] The signs and symptom information on this page attempts to provide a list of some possible signs and symptoms of MHC class 1 or class 2 deficiency.

Diagnostic Tests for MHC Class II Deficiency

MHC class II deficiency, also known as bare lymphocyte syndrome type 2, can be diagnosed through various tests that assess the immune system's function and presence of specific proteins. Here are some diagnostic tests used to identify this condition:

• Complete Blood Cell Count (CBC): A CBC measures the levels of different blood cells, including white blood cells, which helps diagnose MHC class II deficiency.
  • [5] reveals decreased CD4+ counts in patients with MHC class II deficiency.
• Immunoglobulin Assessment: This test evaluates the levels of immunoglobulins (antibodies) in the blood to determine if there is a deficiency in antibody production.
  • [5] mentions that immunoglobulin assessment can help diagnose MHC class II deficiency.
• Flow Cytometry: Flow cytometry measures the presence and function of specific cells, such as T-cells and B-cells, which helps identify MHC class II deficiency.
  • [5] states that flow cytometry reveals decreased CD4+ counts in patients with MHC class II deficiency.
• Genetic Testing: Genetic testing can identify mutations in genes responsible for MHC class II expression, such as RFXANK and RFX5.
  • [4] discusses the strategies used for genetic diagnosis of MHC class II deficiency, including founder mutation screening and study of polymorphic markers.

Early Detection through Newborn Screening

Some patients with MHC class II deficiency can be detected using TREC-based newborn screening assays. This allows for early detection and intervention. + [7] mentions that some patients with MHC class II deficiency can be detected using TREC-based newborn screening assays.

These diagnostic tests help identify MHC class II deficiency, which is essential for prompt diagnosis and effective treatment of this rare primary immunodeficiency disorder.

Current Treatment Options for MHC Class II Deficiency

MHC class II deficiency, also known as bare lymphocyte syndrome type 2, is a rare and life-threatening primary combined immunodeficiency. While there are no specific drug treatments available to cure this condition, various symptomatic care options can help manage the symptoms.

• Prophylactic antibiotics: Patients with MHC class II deficiency often require prophylactic antibiotics to prevent infections (8).
• Immunoglobulin therapy: Intravenous immunoglobulins (IVIG) may be administered in case of low antibody levels or recurrent infections (8).
• Nutritional support: Adequate nutritional support is essential for patients with MHC class II deficiency, as they may experience malabsorption and weight loss (14).

Curative Treatment: Hematopoietic Stem Cell Transplantation

While there are no specific drug treatments available to cure MHC class II deficiency, hematopoietic stem cell transplantation (HSCT) remains the only known curative treatment for this condition (7, 13). However, HSCT is associated with a high risk of toxicity and complications.

Current Research and Future Directions

Recent studies have highlighted the importance of genetic analysis in diagnosing MHC class II deficiency. For example, mutations in RFXANK and RFX5 genes have been identified as contributing to this condition (9, 12). Further research is needed to develop targeted therapies and improve treatment outcomes for patients with MHC class II deficiency.

References:

• [8]
• [7]
• [14]
• [13]
• [9]
• [12]

Differential Diagnosis of MHC Class II Deficiency

MHC class II deficiency, also known as bare lymphocyte syndrome type II (BLS), is a rare congenital combined immunodeficiency disorder characterized by the lack of MHC-II molecules on antigen-presenting cells. The differential diagnosis for this condition includes:

• Pneumocystis pneumonia: This opportunistic infection should be considered in the differential when evaluating any child with lymphopenia and/or severe respiratory symptoms.
• Chronic granulomatous skin disease: This condition can present similarly to MHC class II deficiency, particularly in terms of skin manifestations.
• CIITA deficiency: CIITA is an inducible factor that controls the expression of MHC class II genes. Deficiency in this protein can lead to a similar phenotype to MHC class II deficiency.

Key Features to Consider

When considering the differential diagnosis for MHC class II deficiency, it's essential to note the following key features:

• Lymphopenia: A significant reduction in lymphocyte count is often observed in patients with MHC class II deficiency.
• Respiratory and gastrointestinal infections: Patients with this condition are prone to recurrent respiratory and gastrointestinal infections due to impaired immune function.
• Failure to thrive: Early mortality and failure to thrive are common features of MHC class II deficiency.

References

• [1] CIITA Deficiency - CIITA is an inducible factor that controls the expression of MHC class II genes by binding to the RFX complex and triggering transcription. ...
• [2] Bare lymphocyte syndrome type 1 and 2: A review of the literature.
• [3] Pneumocystis pneumonia in immunocompromised patients.

Note: The references provided are based on the search results within the context.