Given the severity of Patient 2 symptoms (Castrén et al., 2001; Feng et al., 1997), metabolic restriction in GSD models (Ross et al., 2020; Özen, 2007) and high metabolic demand in FXS models (Menzies et al., 2021; Leboucher et al., 2019), we tested here for a negative synergistic interaction between FMRP and PHKA2 functions. The gene discussed is PHKA2; the disease is disorder of glycogen metabolism.