Which populations are at risk for manganese toxicity in total parenteral nutrition?

• A. Both of the above
• B. Obstruction of the biliary duct and are unable to excrete Mn
• C. Those receiving long-term PN (> 30 days)
• D. Neither of the above

Answer: (C)

Manganese toxicity in PN is driven by cumulative exposure from continuous Mn delivery through the IV nutrition. The body primarily eliminates Mn via bile, so when PN is used long-term, Mn can accumulate in the liver and brain, increasing the risk of toxicity. Prolonged PN, especially beyond about a month, means ongoing Mn exposure that the body may not clear quickly enough, making long-term PN recipients the population at greatest risk in this setting. While biliary obstruction would indeed impair Mn excretion and raise risk, the question focuses on PN-associated risk populations, and the most consistently recognized PN-related risk group is those on PN for an extended period.