Major Histocompatibility Complex Class II Deficiency Beyond Infancy.

Area of Science:

• Immunology
• Genetics
• Rare Diseases

Background:

• Major histocompatibility complex class (MHC)-II deficiency is a rare autosomal recessive combined immunodeficiency.
• It accounts for 4.1% of inborn errors of immunity (IEI) in North Africa and the Middle East, with most patients not surviving past age 10.

Observation:

• This study reports four unrelated Moroccan patients with MHC-II deficiency, exhibiting rare and unusual late-onset presentations.
• Patients presented with recurrent pulmonary infections, bronchial dilatation, hemorrhagic rectocolitis, and were diagnosed between ages 16-26.
• Diagnosis was confirmed by absent human leukocyte antigen-DR (HLA-DR) expression and a specific RFXANK mutation (c.338-25_338del).

Findings:

• The mean age of patients was 18.75 years, with diagnosis at a mean age of 14.07 years.
• Three of the four patients (75%) are alive and receiving monthly intravenous immunoglobulin (IVIG) therapy.
• The identified mutation was c.338-25_338del in the RFXANK gene.

Implications:

• MHC-II deficiency should be considered in the differential diagnosis of combined immunodeficiencies across all age groups, not just in children.
• Late-onset cases and survival into adulthood are possible with appropriate management, such as IVIG therapy.
• Further research is needed to understand the diverse clinical phenotypes associated with MHC-II deficiency.