Genetic Analysis Reveals a Missense Mutation in Reactivation Gene-2 (RAG2) Causing Severe Combined Immunodeficiency Disease in a Pakistani Family

Abstract

Objective: To perform clinical and genetic analysis in a family suffering from lymphopenia (low B-lymphocyte, T-lymphocyte and healthy Natural Killer cells). Method: In the current research project we enrolled a female child from Rawalpindi district. Laboratory investigations including lymphocyte subset analysis were performed using anti-antibodies (CD19, CD3, CD4, CD8 and CD16/56). Estimation of serum immunoglobulins was performed. DNA Sanger sequencing of the RAG2 gene was performed to identify the gene mutation. Results: A thorough clinical examination by a team of expert physicians revealed severe nappy rash, interstitial pneumonitis and intractable diarrhoea leading to failure to thrive. Lymphopenia with CD3+CD8 cells (0.1%), CD19 cells (0.1%), CD19/CD56 cells (27%) and CD4/CD8 cells (0.0%) resulting in B-T-NK+ deficiency. The patient’s serum immunoglobulins showed low levels of IgG, IgA and IgM levels. Exons-specific polymerase chain reaction (PCR) was performed using oligonucleotide primers and subsequently DNA Sanger sequenced which resulted in a missense variant in the gene RAG2. Conclusion: In human reactivation genes 1 and 2 encode proteins with endonuclease activity which are involved in V(D)J rearrangement to generate a variety of different types of T- and B- cell receptors. Genetic analysis revealed a missense mutation in RAG2 genes in female SCID patients.