In humans, HCFC1 variants have been associated with X‐linked recessive cobalamin metabolism disorder that presented severe epileptic encephalopathy, intellectual disability, failure to thrive and even early death (designated CblX, MIM #309541)7, 8 and also have been reported in intellectual disability with/without epilepsy but without metabolic disorders.2, 9, 10. Here, HCFC1 is linked to epilepsy.