PPM1K and maple syrup urine disease: Maple syrup urine disease (MSUD; OMIM# 248600) is an inherited autosomal recessive disorder caused by deficiency of branched‐chain alpha‐keto acid dehydrogenase (BCKDH) activity, resulting in impaired metabolism of branched chain amino acid's (BCAA's): leucine (Leu), isoleucine (Iso), and valine (Val).