Because vitamin B6 is present in most foods, dietary deficiency is rare. Secondary deficiency may result from various conditions. Symptoms can include peripheral neuropathy, a pellagra-like syndrome, anemia, and seizures, which, particularly in infants, may not resolve when treated with antiseizure drugs. Impaired metabolism (dependency) is rare; it causes various symptoms, including seizures, intellectual disability, and anemia. Diagnosis is usually clinical; no laboratory test readily assesses vitamin B6 status. Treatment consists of giving oral vitamin B6 and, when possible, treating the cause.
Sources, Functions, and Effects of Vitamins).
Dietary sources of vitamin B6 include organ meats (eg, liver), whole-grain cereals, fish, and legumes. (See also Overview of Vitamins.)
Etiology of Vitamin B6 Deficiency and Dependency
Dietary vitamin B6 deficiency, though rare, can develop because extensive processing can deplete foods of vitamin B6.
Secondary vitamin B6 deficiency most often results from
Excessive loss during hemodialysis
Rarely, secondary deficiency results from increased metabolic demand (eg, in hyperthyroidism).
Symptoms and Signs of Vitamin B6 Deficiency and Dependency
Rarely, deficiency or dependency causes seizures in infants. Seizures, particularly in infants, may be refractory to treatment with antiseizure drugs.
Normocytic, microcytic, or sideroblastic anemia can also develop.
Diagnosis of Vitamin B6 Deficiency and Dependency
Clinical evaluation
Vitamin B6 deficiency should be considered in
Any infant who has seizures
Any patient who has seizures refractory to treatment with antiseizure drugs
Any patient with deficiencies of other B vitamins, particularly in patients with alcohol use disorder or protein-energy undernutrition
Diagnosis of vitamin B6 deficiency is usually clinical. There is no single accepted laboratory test of vitamin B6 status; measurement of serum pyridoxal phosphate is most common.
Pearls & Pitfalls
Treatment of Vitamin B6 Deficiency and Dependency
Elimination of risk factors when possible
Key Points
Deficiency can cause peripheral neuropathy, seborrheic dermatitis, glossitis, and cheilosis, and, in adults, confusion and seizures.
Suspect and diagnose based on clinical findings.
