The value of plasma vitamin B6 profiles in early onset epileptic encephalopathies

Background Recent decades have unravelled the molecular background of a number of inborn errors of metabolism (IEM) causing vitamin B 6 -dependent epilepsy. As these defects interfere with vitamin B 6 metabolism by different mechanisms, the plasma vitamin B 6 profile can give important clues for further molecular work-up. This has so far been investigated in only a small number of patients. Methods We evaluated the vitamin B 6 vitamers pyridoxal 5’-phosphate (PLP), pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN) and the catabolite pyridoxic acid (PA) in the so far largest patient cohort: reference ( n = 50); pyridox(am)ine 5’-phosphate oxidase (PNPO) deficiency ( n = 6); antiquitin (ATQ) deficiency ( n = 21); tissue non-specific alkaline phosphatase (TNSALP) deficiency ( n = 2) and epileptic encephalopathy (EE) of unknown etiology tested negative for ATQ and PNPO deficiency ( n = 64). Results High plasma PM concentration was found in all patients with PNPO deficiency irrespective of vitamin B 6 supplementation. Their PM concentration and the PM/PA ratio was significantly higher ( p