Vitamin B6-dependent epilepsy due to pyridoxal phosphate-binding protein (PLPBP) defect - First case report from Pakistan and review of literature

Introduction: The Vitamin B6-dependent epilepsies are a heterogeneous group of autosomal recessive disorders usually characterized by neonatal onset seizures responsive to treatment with vitamin B6 available as pyridoxine (PN) or as the biologically active form pyridoxal 5-phosphate (PLP). The vitamin B6-dependent epilepsies are caused by mutations in at least five different genes involved in B6 metabolism. A literature review revealed that only 30 patients with vitamin B6-dependent epilepsy caused by PLPBP mutation have been reported worldwide.

Presentation of case: We report a case of baby boy born to first-cousin Pakistani parents who presented with generalized as well as focal seizures starting a few hours after birth and responsive to PLP. Whole exome sequencing revealed a homozygous pathogenic variant NM_007198.4:c.46_47insCA, NP_009129.1:p.Leu17Hisfs, causing a CA duplication resulting in a frameshift in the PLPBP gene.

Discussion: Vitamin B6-Dependent Epilepsy due to PLPBP defect is a rare disorder. The developmental outcomes are variable even with early therapy. Few patients are reported to achieve optimal developmental milestones with therapy. PLP has been advocated as the treatment of choice for PLPBP defect, but oral PN has also demonstrated good seizure control in some patients, including ours.

Conclusion: Vitamin B6-dependent epilepsy due to PLPBP defect is an important differential diagnosis to consider in patients with biochemical features suggestive of pyridoxamine 5'-phosphate Oxidase (PNPO) defect and gene testing can facilitate in reaching the correct diagnosis. Prompt diagnosis and treatment led to excellent seizure control in most patients.