All of the following can cause neuropathies with predominant motor involvement except
Correct Answer: Arsenic intoxication
Description: Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme pyruvate dehydrogenase (PDH) complex, which catalyzes the oxidation of pyruvate to acetyl-CoA by NAD+. With the enzyme inhibited, the energy system of the cell is disrupted resulting in cellular apoptosis. Biochemically, arsenic prevents use of thiamine resulting in a clinical picture resembling thiamine deficiency. Poisoning with arsenic can raise lactate levels and lead to lactic acidosis. Low potassium levels in the cells increases the risk of experiencing a life-threatening hea rhythm problem from arsenic trioxide. Arsenic in cells clearly stimulates the production of hydrogen peroxide (H2O2). When the H2O2 reacts with ceain metals such as iron or manganese it produces a highly reactive hydroxyl radical. Inorganic arsenic trioxide found in ground water paicularly affects voltage-gated potassium channels, disrupting cellular electrolytic function resulting in neurological disturbances, cardiovascular episodes such as prolonged QT interval, neutropenia, high blood pressure,central nervous system dysfunction, anemia, and death. Ref Harrison20th edition pg 1334
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