Major Histocompatibility Complex (MHC) Class II Deficiency- A Case of Primary Immunodeficiency Disorder.

Area of Science:

• Immunology
• Genetics

Background:

• Major Histocompatibility Complex (MHC) Class II deficiency is a rare primary immunodeficiency.
• It results from mutations in genes regulating MHC Class II protein expression.
• Clinical features include severe infections, failure to thrive, and potential early mortality.

Observation:

• A 9-month-old girl experienced recurrent pneumonia requiring hospitalization and ventilation.
• Physical examination revealed absent tonsils, sparse hair, seborrhea, and hepatosplenomegaly.
• Imaging showed pulmonary infiltrates and ground-glass opacities.

Findings:

• Lymphocyte subset analysis indicated lymphocytopenia.
• HLA typing demonstrated absent HLA-DR expression on B cells, consistent with MHC Class II deficiency.
• Genetic analysis revealed a homozygous mutation in the RFX-5 gene (RFX5: c.848_849del:p.R283Tfs*6).

Implications:

• This case highlights the severe presentation of MHC Class II deficiency.
• Early diagnosis and genetic identification are crucial for understanding and managing this condition.
• Prenatal diagnosis counseling is essential for affected families.