PPM1K and metabolic disease: Maple Syrup Urine Disease (MSUD) is a rare inherited metabolic disorder affecting 1 in 100,000 to 300,000 newborns (Piri-Moghadam et al. 2022a) and characterized by deficiencies in BCKDH (Yang et al. 2021; Billington et al. 2022; Yokoi et al. 2022).