D81.7 Major histocompatibility complex class II deficiency

Name of the Condition

• Major histocompatibility complex class II deficiency

Summary

Major histocompatibility complex (MHC) class II deficiency is a rare inherited disorder characterized by impaired immune responses due to defects in MHC class II molecules. These molecules are essential for presenting antigens to CD4+ T cells, which coordinate adaptive immunity. The deficiency leads to reduced T-cell activation, poor antibody production, and increased susceptibility to infections, particularly from bacteria, viruses, and fungi. The condition typically presents in early childhood with recurrent or severe infections.

Causes

MHC class II deficiency is caused by genetic mutations in genes involved in the regulation or expression of MHC class II molecules, such as CIITA, RFX5, RFXAP, or RFXANK. These mutations disrupt the transcription or assembly of MHC class II proteins, preventing their proper function. Inheritance is autosomal recessive, meaning both copies of the gene must be mutated for the condition to manifest.

Risk Factors

• Genetic predisposition, often with a family history of immunodeficiency disorders.
• Consanguinity (parents who are closely related) increasing the risk of autosomal recessive forms.
• Certain ethnic backgrounds with higher prevalence of specific genetic mutations.

Symptoms

• Recurrent, severe, or persistent infections (e.g., bacterial, viral, fungal).
• Chronic diarrhea or failure to thrive in infants and children.
• Respiratory infections, including pneumonia or bronchitis.
• Skin infections or rashes.
• Delayed growth or development.

Diagnosis

Diagnosis involves clinical evaluation of recurrent infections and immune function testing. Laboratory tests may show reduced CD4+ T-cell counts, low immunoglobulin levels, and poor response to vaccines. Genetic testing confirms mutations in MHC class II-related genes. Flow cytometry or molecular assays assess MHC class II expression on immune cells. Differential diagnosis excludes other immunodeficiencies with similar presentations.

Treatment Options

Treatment focuses on managing infections and supporting immune function. Antibiotics, antivirals, or antifungals treat active infections. Immunoglobulin replacement therapy may be used to boost antibody levels. Hematopoietic stem cell transplantation (HSCT) is the only curative option, aiming to restore normal immune function. Supportive care includes prophylactic medications and nutritional support.

Prognosis and Follow-Up

Prognosis depends on early diagnosis and treatment. Untreated, the condition can be life-threatening due to severe infections. HSCT improves survival and immune function in many cases, but outcomes vary based on donor matching and complications. Long-term follow-up includes monitoring for infection recurrence, immune reconstitution, and potential transplant-related issues. Regular immunological assessments guide ongoing care.

Complications

• Severe or life-threatening infections (e.g., sepsis, meningitis).
• Chronic lung disease from recurrent respiratory infections.
• Malnutrition or growth failure.
• Increased risk of autoimmune disorders or malignancies due to immune dysregulation.
• Complications from HSCT, such as graft-versus-host disease.

Lifestyle & Prevention

• Practice good hygiene to reduce infection risk (e.g., handwashing, avoiding sick contacts).
• Ensure up-to-date vaccinations (where appropriate) and avoid live vaccines.
• Maintain a balanced diet to support overall health.
• Avoid exposure to pathogens (e.g., contaminated water, uncooked foods).
• Follow medical advice for prophylactic treatments or immunizations.

When to Seek Professional Help

Seek immediate medical attention for:

• High fever or signs of severe infection (e.g., difficulty breathing, lethargy).
• Persistent or worsening symptoms despite treatment.
• Unusual rashes, swelling, or other signs of immune-related issues.
• Concerns about growth or development in children.

Tips for Medical Coders

Document the diagnosis of MHC class II deficiency with specificity, including clinical findings (e.g., recurrent infections, immune testing results) and genetic confirmation if available. Ensure the code D81.7 is assigned when the condition is clearly identified. Note any associated complications or treatments, as these may impact coding for related encounters. Avoid using this code for unrelated immunodeficiencies or non-specific immune disorders.