from Section IV - Metabolic Liver Disease
Published online by Cambridge University Press: 19 January 2021
The porphyrias are metabolic disorders each resulting from the deficiency of a specific enzyme in the heme biosynthetic pathway (Figure 30.1 and Table 30.1) [1–6]. These enzyme deficiencies are inherited as autosomal dominant, autosomal recessive and X-linked traits, with the exception of porphyria cutanea tarda (PCT), which usually is sporadic. The porphyrias are classified as either hepatic or erythropoietic depending on the primary site of overproduction and accumulation of porphyrin precursors or porphyrins (Table 30.2) although some have overlapping features. The hepatic porphyrias are characterized by overproduction and initial accumulation of porphyrin precursors and/or porphyrins primarily in the liver, whereas in the erythropoietic porphyrias, overproduction and initial accumulation of the pathway intermediates occur primarily in bone marrow erythroid cells.
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