PPM1K defects cause mild maple syrup urine disease: The second case in the literature

Abstract

AbstractMaple syrup urine disease (MSUD) is an inborn error of metabolism caused by the insufficient catabolism of branched‐chain amino acids. BCKDHA, BCKDHB, DBT, and DLD encode the subunits of the branched‐chain α‐ketoacid dehydrogenase complex, which is responsible for the catabolism of these amino acids. Biallelic pathogenic variants in BCKDHA, BCKDHB, or DBT are characteristic of MSUD. In addition, a patient with a PPM1K defect was previously reported. PPM1K dephosphorylates and activates the enzyme complex. We report a patient with MSUD with mild findings and elevated BCAA levels carrying a novel homozygous start‐loss variant in PPM1K. Our study offers further evidence that PPM1K variants cause mild MSUD.