In porphyria cutanea tarda (PCT), the diagnostic finding on urine fluorescence/Woods lamp examination is pink-red fluorescence due to accumulation of which compound?
- A Protoporphyrin IX
- B Uroporphyrin I and III ✓
- C Delta-aminolevulinic acid (ALA)
- D Porphobilinogen (PBG)
Correct answer: B. Uroporphyrin I and III
Explanation
PCT results from deficiency of uroporphyrinogen decarboxylase (URO-D), causing uroporphyrinogen to oxidise to uroporphyrin I and III. Uroporphyrins are water-soluble and excreted in urine; under Wood's lamp (365 nm UV) they fluoresce vivid pink-coral-red. The 'tea-coloured' urine reflects urinary uroporphyrin in ambient light. PCT is the most common porphyria and is associated with alcohol use, HCV infection, hemochromatosis (iron overload inhibits URO-D), and HCB exposure. Treatment includes phlebotomy (to reduce hepatic iron) and low-dose hydroxychloroquine.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.