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

Major Histocompatibility Complex (MHC) Class II deficiency is a rare autosomal recessive primary immunodeficiency caused by mutations in regulatory genes of MHC Class II proteins. Clinical manifestations include respiratory/gastrointestinal infections, failure-to-thrive, septicemia and early death. A 9-mo-old-girl presented with repeated episodes of pneumonia requiring hospitalization and ventilator support since the last 5 mo. Examination revealed absent tonsils, sparse scalp-hair, seborrhea and firm hepato-splenomegaly. Radiograph showed absence of thymic shadow with diffuse pulmonary infiltrates. CT scan showed multiple bilateral ground glass pulmonary opacities with patchy consolidation. Primary immunodeficiency disorder was suspected in view of repeated pulmonary infections, failure to thrive and suggestive family history. Lymphocyte subset assay revealed lymphocytopenia and HLA typing showed absence of HLA-DR expression on B cells suggestive of MHC Class II deficiency. Targeted gene panel detected a homozygous mutation in the RFX-5 gene (RFX5: c.848_849del:p.R283Tfs*6;Homozygous). Though this patient succumbed, parents have been counseled regarding need for prenatal diagnosis.