​A 47-year-old man with chronic depression and tonic-clonic seizures, being prescribed paroxetine, maprotiline, lorazepam, and lamotrigine, presented with intense psychomotor agitation that was treated with propofol. Twenty-four hours later, a green-colored urine was observed (Fig. 1⇓ ). A diagnosis of acute porphyria was considered. The green urine showed red fluorescence when irradiated under ultraviolet light and Hoesch test was positive for porphobilinogen screening. Precursor and porphyrin concentrations in a 24-h urine were within reference limits.

  1. What are the most frequent causes of green discoloration of urine?
  2. When porphyrins are present in large amounts, what is the most likely color of urine?
  3. What interfering compounds can cause a false-positive Hoesch test result?
  4. What is the likely cause for the green urine in this patient?

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