Investigations

• urine - colour and porphyrin level are diagnostic. The patient may have burgundy red urine if uroporphyrin is present and this is a constant finding in congenital erythropoietic porphyria. Urine in acute intermittent porphyria becomes brown, red or black on standing whilst that of porphyria cutanea tarda shows a pink fluorescence when illuminated. Particular porphyrins raised except in erythropoietic protoporphyria.
  
  
• serum - specific porphyrins raised except in variegate porphyria. Increase is moderate in porphyria cutanea tarda.
  
  
• stool - specific porphyrins raised except in acute intermittent porphyria.

Reference

1. Wang B, Bonkovsky HL, Lim JK, et al. AGA clinical practice update on diagnosis and management of acute hepatic porphyrias: expert review. Gastroenterology. 2023 Mar;164(3):484-91.
2. Karim Z, Lyoumi S, Nicolas G, et al; Porphyrias: A 2015 update. Clin Res Hepatol Gastroenterol. 2015 Jul 1. pii: S2210-7401(15)00120-5.