To define ID in areas with high burden of infectious diseases, the World Health Organization (WHO) recommends the use of low ferritin concentrations (< 12 μg/L in children < 5 years or < 15 μg/L in children ≥ 5 years), with an arbitrarily higher cut-off of ferritin (< 30 μg/L) in children < 5 years with inflammation (defined as C-reactive protein (CRP) > 5 mg/L) [7, 8]. The gene discussed is CRP; the disease is infectious disease.