The mean plasma concentration of FGF-21 in MD patients was of 440 pg/mL (range 55–2908 pg/mL), of 224 pg/mL in non-MD patients (range 1–1867 pg/mL), and of 187 pg/mL in healthy controls (range 24–727 pg/mL). The gene discussed is FGF21; the disease is Menkes disease.