Early diagnosis of MLD that can be achieved by newborn screening (NBS) via liquid chromatography–tandem mass spectrometry (LC–MS/MS) by a two‐tier approach, which includes quantitation of the C16:0 sulfatide, and assay of ARSA activity in dried blood spots (DBS).3, 10, 11, 12. The gene discussed is ARSA; the disease is metachromatic leukodystrophy.