Question: The urine collected on the left darkened to the reddish-purple colour on the right after exposure to sunlight. Which condition is responsible for this finding?

Answer: This finding is due to porphyria. Porphyrias are rare disorders of heme synthesis with several phenotypes. The classic observation in acute intermittent porphyria is of dark urine following an attack, or darkening of urine after exposure to sunlight, due to buildup of porphyrins in the specimen.