The median (first quartile‐third quartile) of serum GDF15 concentrations measured with the LTIA device was significantly higher (P < .001) in MD patients (1389.0 U/mL [869.5‐1776.0 U/mL]) than in healthy controls (380.5 U/mL [330.2‐471.8 U/mL]); the interquartile ranges did not overlap between MD patients and healthy controls. The gene discussed is GDF15; the disease is Menkes disease.