A 6-year-old girl presented with history of infantile onset epileptic
encephalopathy and developmental delay. She had polymorphic
seizures that were refractory to regular anti-seizure medication. Incomplete control of
seizures was achieved on starting
pyridoxine,
riboflavin and
thiamine. Clinical exome sequencing done at 4 years revealed
PNPO deficiency with a homozygous mutation in the highly conserved exon 3:c.352G > A p.Gly118R region of the gene. Thereafter,
pyridoxine was weaned and
pyridoxal phosphate was added with resultant refractory
status epilepticus, which necessitated our approach to start
pyridoxine and stop
pyridoxal phosphate. With two antiseizure medication and three
vitamins, she had improved seizure control. At 6 years of age an attempt to wean off
riboflavin resulted in break through
seizures. After restarting
riboflavin along with
pyridoxal phosphate,
pyridoxine in low doses and two antiseizure medications, the child achieved good seizure control. Though partial responsiveness to
pyridoxine with gene mutation in the exon 3: c.352G > A p. Gly118R is known,
riboflavin dependence and transient worsening of
seizures off
pyridoxine has not been described to our knowledge. Our case highlights the importance of identifying the precise gene mutationsequence to properly identify variants relative to individual phenotypic expression, treatment responsivness and need for added
vitamin supplementation.