Biallelic pathogenic ST3GAL5 variants led to disrupted synthesis of a- and b-series gangliosides, and consequently to severe infantile-onset neurological disorders characterized by progressive microcephaly, intellectual disability, choreoathetosis, blindness, deafness, intractable seizures, and/or pigment changes [51,52,53,54,55,56,57,58,59]. The gene discussed is ST3GAL5; the disease is microcephaly.