Snapshot A 24-year-old woman presents to her primary care physician due to fatigue, nightsweats, cough, and fever. She reported to being in her usual state of health until a few weeks after returning from her trip to Mexico. She has been experiencing these symptoms for approximately 2 weeks. A chest radiograph is performed, which shows mild pulmonary scarring. After further workout she was found to have tuberculosis infection. She is started on rifampin, isoniazid, vitamin B6, pyrazinamide, and ethambutol. (Primary tuberculosis infection) Introduction Vitamin B6 is a water soluble vitamin (and thus excreted in the urine) and is a collective term for pyridoxine pyridoxal pyridoxamine Biochemistry vitamin B6 serves as a precursor for pyridoxal phosphate (PLP) PLP is a coenzyme for a number of enzymes (e.g., glycogen phosphorylase) involved in various enzymatic reactions such as transamination decarboxylation synthesis of heme neurotransmitters cystathione niacin histamine Clinical correlate vitamin B6 deficiency can result from isoniazid therapy used to treat tuberculosis infection therefore, vitamin B6 is administered with isoniazid oral contraceptives vitamin B6 deficiency can present with peripheral neuropathy (rare) sideroblastic anemia hyperirritability pyridoxine-dependent epilepsy stomatitis glossitis cheilosis depression confusion elevated homocysteine levels seizures more common with isoniazid use pyridoxine is treatment of seizures caused by B6 deficiency vitamin B6 toxicity can present (typically in large doses) with peripheral neuropathy dermatoses photosensitivity