Thiamine (Vitamin B1) deficiencies are primarily seen in alcoholic patients. This scenario is so common on Step 1 that anytime you see alcoholism in a vitamin question, your first thought should be thiamine deficiency. Thiamine is found in a lot of different foods, so you usually only see deficiencies in people who are malnourished or getting a majority of their calories from alcohol. Deficiencies of Thiamine primarily affect 3 different areas; the CNS (Wernicke-Korsakoff Syndrome), PNS (Dry Beri-Beri), and the cardiac system (Wet Beri-Beri). Damage done to the cardiac system and the PNS can be reversed with treatment, but damage done to the CNS is permanent.
Thiamine is an important cofactor in multiple processes that generate ATP from glucose sugar. Therefore, deficiencies are worsened by sugar intake (in the absence of thiamine administration) because the little bit of Thiamine left in the system is used up to metabolize the sugar.
Wernicke-Korsakoff Syndrome is the collection of CNS damage that results from Thiamine deficiency. It includes amnesia (memory loss), confusion, ataxia (unsteady gait), and visual disturbances due to uncoordinated eye movement. The confusion and memory loss can lead to confabulation in which the patient has bizarre explanations for things like how they got injured. Wernicke-Korsakof syndrome characteristically affects the Mammillary Bodies and the surrounding structures (3rd/4th ventricle & aqueduct). Infarcts or hemorrhages in these areas can be seen on radiologic imaging.
Dry BeriBeri is damage to the peripheral nervous system (PNS) that results from Thiamine deficiency. It causes muscle wasting, weakness, and diminished peripheral sensation. Wet BeriBeri is the cardiac effects of Thiamine deficiency. It leads to arrhythmias and/or heart failure by affecting the electrical system of the heart. Edema, dyspnea, increased cardiac output, and cardiac dilation can result.
Niacin (Vitamin B3) is part of NAD+ and NADP+ which carry electrons in redox reactions. Vitamin B3 is made from tryptophan using a vitamin B6 cofactor. Therefore, Niacin deficiency can be the result of Vitamin B6 deficiency or tryptophan deficiency (Hartnup Disease or Carcinoid Syndrome).
Niacin deficiency is called Pellagra. Pellagra is characterized by the “4 Ds” Diarrhea, Dementia, Dermatitis, and Death. Niacin is one way to treat high cholesterol. Niacin toxicity can result if a patient receives too high of a dose. This causes the side effect of Facial Flushing (red face with the sensation of warmth).
Pyridoxine (Vitamin B6) is an essential coenzyme in many metabolic reactions. Deficiencies can cause peripheral neuropathy (numbness & tingling), seizures, anemia & irritability. Deficiencies of Vitamin B6 can also lead to deficiencies of Vitamin B3, because B6 is a cofactor in the pathway that converts Tryptophan to Vitamin B3. The most common cause of Vitamin B3 deficiency is Isoniazid (TB drug) Treatment. Therefore, some patients receiving Isoniazid are given B6 vitamins prophylactically.
Vitamin C (Ascorbic Acid) is involved in the hydroxylation of certain amino acids in collagen that are important for crosslinking individual pro-collagen chains into a triple helix. Without this hydroxylation the collagen is very weak. Therefore, deficiencies of Vitamin C cause poor wound healing, gum abnormalities (pain, bleeding & loose/missing teeth) & bruising (purpura, ecchymosis, perifollicular hemorrhages). Scurvy results from not eating enough fruit and other fresh foods.