Chapter 32 - Porphyria

Summary

The porphyrias are a group of conditions in which there are deficiencies in one of the eight enzymes of the heme biosynthetic pathway (the porphyrin pathway): four of the enzymes are located in the mitochondria and the other four in the cytosol. There are three acute porphyrias which cause epilepsy and other neurological symptoms: acute intermittent porphyria (AIP), variegate porphyria, and hereditary coproporphyria (HCP). This chapter discusses the clinical features, diagnostic tests and treatment options for porphyria. The diagnosis of acute porphyria depends on demonstrating increased levels of urinary d-aminolevulinic acid (ALA) and porphobilinogen (PBG) in urine. Genetic testing can confirm the disease, but as there are many different mutations in the PBGD gene it is not used widely for screening purposes. Non-enzyme-inducing drugs such as gabapentin, pregabalin, topiramate, or levetiracetam are much safer. For acute therapy, diazepam and clonazepam are relatively safe. Magnesium sulfate has also traditionally been used.