PI4KA and polymicrogyria: Polymicrogyria is also a symptom in disorders resulting from PIK4CA (phosphatidylinositol 4-kinase), FIG4 (phosphoinositide 5-phosphatase) and AKT3 mutations (Baulac et al., 2014; Pagnamenta et al., 2015), while mutations in the 5-phosphatase domain of polyphosphate 5-phosphatase INPP5E manifests as the ciliopathy Joubert Syndrome 1 (Bielas et al., 2009) characterized by cerebellar hypoplasia/aplasia (incomplete development of cerebellum), thickened cerebellar peduncles and abnormally large interpeduncular fossa (‘molar tooth sign’) (Travaglini et al., 2013; Shetty et al., 2017).