1. Intermittent Unexplained Abdominal Pain: Is It Porphyria?
Joseph R. Bloomer, Brendan M. McGuire 
Clinical Gastroenterology and Hepatology 
Volume 5, Issue 11, Pages (November 2007)
DOI: /j.cgh
Copyright © 2007 AGA Institute Terms and Conditions

2. Figure 1
Hepatic heme metabolism. Under normal conditions, the rate-limiting enzyme in the hepatic heme biosynthesis pathway, ALA synthase-1, is under negative feedback control by a putative regulatory heme pool. During an acute porphyric attack, ALA synthase-1 is markedly induced, causing increased synthesis of ALA, PBG, and porphyrins. In the presence of downstream enzyme defects, this causes excess accumulation and excretion of these compounds. Together with the downstream enzyme defect, this causes excess accumulation and excretion of ALA and PBG. (1) Drugs such as phenobarbital cause ALA synthase-1 induction by increasing the level of heme-containing cytochrome P450, thus depleting the regulatory heme pool. (2) Fasting causes an increase in the level of peroxisome proliferator–activated receptor γ coactivator 1α in the hepatocyte, which directly induces ALA synthase-1. (3) Infection induces heme oxygenase, which increases heme degradation, and thus necessitates increased heme synthesis to maintain biostasis.
Clinical Gastroenterology and Hepatology 2007 5, DOI: ( /j.cgh )
Copyright © 2007 AGA Institute Terms and Conditions

3. Figure 2
Algorithm for managing the acute porphyric attack. This management strategy is used for all of the acute porphyrias during an acute attack. When the patient has been diagnosed previously with acute porphyria on the basis of clinical features and biochemical tests, it is not necessary to assess the level of urine PBG if the patient is having symptoms consistent with an acute attack.
Clinical Gastroenterology and Hepatology 2007 5, DOI: ( /j.cgh )
Copyright © 2007 AGA Institute Terms and Conditions