As the patient presented with CVID and unexplained systemic inflammation, targeted next-generation sequencing of known CVID-related genes (ICOS, TNFRSF13B, CD19, TNFRSF13C, MS4A1, CD81, CR2, LRBA, NFKB2, IL21, NFKB1, IKZF1, PLCG2, CTLA4, and MSN) was performed at the Kazusa DNA Research Institute (Kisarazu, Chiba, Japan), which identified no pathogenic mutations. Here, MSN is linked to common variable immunodeficiency.