A 27-year-old woman goes to an emergency room with severe abdominal pain. She had previously experienced similar episodes of pain that lasted several hours to a few days, but this episode is the most severe. She has also been experiencing nausea, vomiting, and constipation. The physician is left with the impression that she is agitated and somewhat confused, and an accurate history is difficult to elucidate. The patient is sent for emergency laparotomy, but no pathology is noted at surgery. Following the unrevealing surgery, an older surgeon comments that he had once seen a similar case that was actually due to porphyria.The porphyrias are biochemical abnormalities in which of the following pathways?

The porphyrias are a group of rare, related diseases that have in common a block in the heme synthesis pathway. The block is usually paial rather than complete, and thus many of these patients have only intermittent symptoms. Most cases of porphyria present with either a neurovisceral pattern (including both psychiatric symptoms and abdominal pain) or with photosensitive skin lesions. These two patterns are associated with different forms of porphyria. Must know: Associate abnormalities of glycogen degradation (with the glycogen storage diseases, such as Von Gierke disease, Pompe disease, and Forbes disease. Associate abnormalities of lipoprotein degradation with some forms of hyperlipoproteinemia (notably Type I). Associate abnormalities of nucleotide degradation with Gout and Lesch-Nyhan syndrome. Ref: Murray R.K. (2011). Chapter 31. Porphyrins & Bile Pigments. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.