eMedicine Specialties > Endocrinology > Metabolic Disorders
Pyridoxine Deficiency: Differential Diagnoses & Workup
Updated: Dec 8, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Differential Diagnoses
Other Problems to Be Considered
Homocystinemia
Workup
Laboratory Studies
- Serum PLP is the primary active pyridoxal form and is used as the primary index of whole-body pyridoxal levels.
- Levels of 4-pyridoxic acid can be measured in the urine.13 This compound is the major inactive metabolite of pyridoxine metabolism and its levels normally are 128-680 nmol per nmol of creatinine. Excretion of this compound reflects the pyridoxine body pool in the absence of an exogenous pyridoxine load. Urine levels of 4-pyridoxic acid are lower in females than in males and will be reduced in persons with riboflavin deficiency. Neither age nor alcohol intake effects the measured level.
- Erythrocyte aspartate aminotransferase (EAST) and the EAST activation coefficient (EAST-AC) are long-term indicators of functional pyridoxine status due to the 120-day life span of erythrocytes. EAST-AC reduction lags behind the onset of the pyridoxine deficiency. Thus, a low EAST-AC value confirms a subacute to chronic deficiency state. Chronic alcoholism causes these indexes to be falsely low; in addition, these indexes decrease with age. Hemolytic anemia reduces the life span of erythrocytes.
- Conversion of tryptophan to niacin relies on pyridoxine-dependent enzymes. A tryptophan load of 50-100 mg/kg is administered, and the urinary excretion of tryptophan metabolites is measured. High excretion of kynurenine, kynurenic acid, and xanthurenic acid indicates a functional deficiency in pyridoxine-dependent enzymes. This test is influenced by protein intake, exercise, lean body mass, and pregnancy. Hormonal factors and infections enhance tryptophan-to-niacin conversion. Thus, this test is most useful for monitoring an individual's response to pyridoxine supplementation rather than for diagnosing a deficiency.
- If arteriosclerosis is present, the homocysteine level should be measured.14
- Hematologic indexes may indicate the presence of a hypochromic-microcytic anemia with normal iron levels. Patients with inherited sideroblastic anemias have marked red blood cell dimorphism, anisocytosis, and poikilocytosis.
Other Tests
- Electroencephalogram findings in neonates and infants with pyridoxine-dependent seizures are characterized by repetitive runs of high-voltage, generalized, bilateral, synchronous 1- to 4-Hz spikes and sharp wave bursts.
- Normalizing electroencephalogram findings or causing clinical cessation of seizures by injecting 100 mg of intravenous pyridoxine identifies pyridoxine-dependent and pyridoxine-responsive seizures.
More on Pyridoxine Deficiency |
| Overview: Pyridoxine Deficiency |
 Differential Diagnoses & Workup: Pyridoxine Deficiency |
| Treatment & Medication: Pyridoxine Deficiency |
| Follow-up: Pyridoxine Deficiency |
| References |
| Further Reading |
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References
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Khayat M, Korman SH, Frankel P, et al. PNPO deficiency: an under diagnosed inborn error of pyridoxine metabolism. Mol Genet Metab. Aug 2008;94(4):431-4. [Medline].
Morris MS, Picciano MF, Jacques PF, et al. Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr. May 2008;87(5):1446-54. [Medline].
Woolf K, Manore MM. Elevated plasma homocysteine and low vitamin B-6 status in nonsupplementing older women with rheumatoid arthritis. J Am Diet Assoc. Mar 2008;108(3):443-53; discussion 454. [Medline].
Baggot PJ, Eliseo AJ, DeNicola NG, et al. Pyridoxine-related metabolite concentrations in normal and Down syndrome amniotic fluid. Fetal Diagn Ther. 2008;23(4):254-7. [Medline].
Balasa VV, Kalinyak KA, Bean JA, et al. Hyperhomocysteinemia is associated with low plasma pyridoxine levels in children with sickle cell disease. J Pediatr Hematol Oncol. Jun-Jul 2002;24(5):374-9. [Medline].
Keywords
pyridoxine deficiency, vitamin deficiency, vitamin B, vitamin B6, pyridoxine, vitamin B deficiency, pyridoxine 5'-phosphate, pyridoxal 5'-phosphate, PLP, vitamin B-6 deficiency, malnutrition, peripheral neuropathy, poor diet, pyridoxine-dependent seizures, hereditary sideroblastic anemia, cirrhosis, hemodialysis, peritoneal dialysis, chronic renal failure, homocystinuria, homocystinemia, Gyromitra poisoning, mushroom poisoning, fungus toxicity, mushroom toxicity
