A 7-Month-Old Boy Is Evaluated in the Clinic for Recurrent $\gamma$

Multiple Choice

A 7-month-old boy is evaluated in the clinic for recurrent bacterial infections.His tonsils are not visible on physical examination.Serum immunoglobulin A (IgA) and IgG levels are markedly decreased,and serum IgM levels are slightly below normal.Based on this family's history and clinical presentation,a mutation in which of the following genes is most likely to be found in this patient?

A) JAK3 kinase
B) Adenosine deaminase
C) Common cytokine receptor $\gamma$ chain
D) RAG2
E) Purine nucleoside phosphorylase