Bone loss in CID is driven by both suppressed bone formation and enhanced bone resorption, and TNF‐alpha inhibitor therapy has been shown to normalize markers of bone turnover.(36, 37) Given the hypothetical links between CPP and bone turnover, we hypothesized that treatment of active CID with infliximab would lower circulating CPP levels and be temporally related to changes in markers of bone turnover. The gene discussed is TNF; the disease is combined immunodeficiency.