•Pyridoxine-dependent epilepsy•Pyridoxal phosphate-responsive epilepsy•Early-onset vitamin B6-dependent epilepsy•Cerebral folate deficiency•Methylenetetrahydrofolate reductase deficiency•Molybdenum cofactor deficiency•Biotinidase deficiency•Holocarboxylase synthetase deficiency. Here, HLCS is linked to sulfite oxidase deficiency due to molybdenum cofactor deficiency.