A 42-year-old lady with genetically confirmed however asymptomatic Huntington illness (HD) offered with a 2-year historical past of tingling alongside the lateral legs, intermittent band-like sensations within the legs that resolved with strolling and worsened throughout relaxation, and searing ache from the knee down. She additionally seen nocturnal leg jerking on days when she had vitality drinks. She had no weak point, decrease again ache, or bowel or bladder dysfunction. Household historical past was notable for HD in her brother and each dad and mom. There was no vital alcohol use or different components which will have contributed to her signs. Neurologic examination confirmed hyperreflexia in her legs however was in any other case regular (together with intact notion of pinprick, mild contact, and proprioception). She took duloxetine for nervousness and despair and zolpidem for insomnia. Diagnostic analysis for a number of sclerosis, rheumatoid arthritis, and lupus was inconclusive. MRI confirmed delicate C4–C7 posterior disk protrusions however no vital central or neural foraminal stenosis. Laboratory research at presentation confirmed an elevated vitamin B6 (B6 or pyridoxine) degree of 161.6 ng/mL (regular 2.1–21.7 ng/mL) and regular or adverse full blood rely differential, metabolic profile (together with fasting glucose), thyroid-stimulating hormone, vitamin B12, methylmalonic acid, antinuclear antibody, and Sjögren display. Electrodiagnostic research confirmed no proof of energetic lumbosacral radiculopathy or giant fiber neuropathy. Extra historical past obtained following the invention of elevated B6 ranges revealed that the affected person had consumed 2 vitality drinks per day (40 mg of B6 every) for at the least a 12 months and one multivitamin pill per day (100 mg of B6 every) for a few years. One and a half months after stopping these sources of B6, the affected person had dramatic enchancment of her signs with solely uncommon and transient recurrence.
DISCUSSION
B6 is a water-soluble vitamin necessary in amino acid metabolisms that has been used to deal with numerous circumstances.1 Whereas excessive doses (>2,000 mg a day) have been proven to wreck dorsal root ganglia,2 the impact of decrease B6 doses isn’t well-established. In a retrospective sequence of 26 sufferers with a imply B6 degree of 68.8 ng/mL, sensory signs had been reported in 80.8%.3 One other research of girls taking B6 at 117 ± 92 mg/day for two.9 ± 1.9 years reported paresthesia, bone pains, hyperesthesia, muscle weak point, fasciculations, and numbness.4 It’s fascinating that the controls on this research had been taking the same dose however for a shorter length of time. Thus, length of supplementation seems to play an necessary position in toxicity.4
Alternatively, a latest research reported a scarcity of correlation between B6 and neuropathy.5 On this research, common B6 consumption within the research group was 2.1 mg/day with common serum B6 of 135 nmol/L, whereas in controls common consumption was 2.8 mg/day with common serum B6 of 165 nmol/L (regular 26–102 nmol/L).5 Of be aware, the B6 consumption and serum B6 ranges on this research had been decrease than in different research that thought-about B6 as a potential reason behind neuropathic signs.3,–6 Moreover, this research estimated consumption via a questionnaire, which can not replicate the precise consumption.5 Inadvertent B6 consumption is feasible, as dietary supplements and lots of standard merchandise like cereals, body-building dietary supplements, vitality bars, and drinks have excessive B6 content material.7 However, this research means that B6 can accumulate within the physique even at low doses with persistent use.5 Why B6, a water-soluble vitamin, can accumulate to poisonous ranges is probably going associated to the excessive protein binding of B6 metabolites and B6’s lengthy half-life (∼15–20 days).8 These components might clarify the commentary that solely about 93% of B6 consumption was excreted following IV B6 infusion, and B6 metabolite ranges remained elevated throughout supplementation and for at the least 2 months afterward.9 The authors additionally instructed that storage of B6 does happen, presumably within the liver.9 How elevated B6 ranges trigger nerve harm isn’t clearly established, however potential mechanisms embody the direct toxicity of pyridoxal-5-phosphate metabolite10 and the adverse impact of B6 on ranges of different B nutritional vitamins.11
We imagine that B6 intoxication is the reason for sensory signs in our affected person. This conclusion is supported by the observations that the serum degree exceeds the higher restrict of regular by severalfold, reduction of signs occurred after cessation of B6 ingestion, and no different causes could possibly be recognized. Our case is exclusive in that B6 intoxication is attributable to vitality drinks and dietary supplements. Physicians and sufferers ought to pay attention to the a number of sources of B6 that may probably result in intoxication. With the recognition of merchandise with excessive B6 content material, research of threshold neurotoxic B6 doses are wanted.
STUDY FUNDING
No focused funding reported.
DISCLOSURES – “b vitamin overdose energy drinks”
S.R.S. Sista and D. Lozowska report no disclosures. L.W. Katzin serves on audio system’ bureaus for and has obtained funding for journey and/or speaker honoraria from Grifols and Baxter. T.H. Vu serves on the audio system’ bureau for and has obtained funding for journey and/or speaker honoraria from Allergan. Full disclosure kind info offered by the authors is obtainable with the total textual content of this text at
http://cp.neurology.org/lookup/doi/10.1212/CPJ.0000000000000142.
Notes
Correspondence to:
ude.fsu.htlaeh@6uvt
Funding info and disclosures are offered on the finish of the article. Full disclosure kind info offered by the authors is obtainable with the total textual content of this text at
http://cp.neurology.org/lookup/doi/10.1212/CPJ.0000000000000142.
Footnotes