How are Disorders of Porphyrin Metabolism diagnosed?
Each type of porphyria is defined by specific symptoms and diagnostic signs or “markers,” although these overlap considerably in some types. If a disorder of porphyrin metabolism is suspected on the basis of symptoms, diagnostic tests are usually ordered of urine and stool and sometimes also of blood and plasma to look for characteristic abnormalities of enzyme(s), porphyrin(s) and/or porphyrin “precursors” (substances called ALA and PBG which are measured to check the activity of the first two enzymes in the heme pathway). If acute porphyria is suspected, this testing must be done when patients symptoms are worse than usual. Chemically-acquired porphyrinopathies are more variable and often mimic one or more elements of the different inherited types, but they can be tested and treated in the same way. Since ALA and PBG are always elevated in urine during acute attacks, these porphyrin precursors are sometimes used alone for screening potential cases. They may normal, however, in latent
