SMPD4 and microcephaly: The loss of function of SMPD4 will induce endoplasmic reticulum (ER) stress, autophagy, impaired sphingolipids homeostasis, cell cycle dysregulation, and this could partially explain the severe growth failure and microcephaly in SMPD4-related disorder (Magini et al., 2019; Bijarnia-Mahay et al., 2022).