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INTRODUCTION

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  • The porphyrias are inherited or acquired disorders in which the activity of an enzyme in the heme biosynthetic pathway is altered. Metabolic intermediates are produced in excess, initially either in the marrow or the liver, and result in neurologic and/or photocutaneous symptoms and signs.

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CLASSIFICATION

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  • See Table 28–1.

  • The two organs most active in heme biosynthesis are the marrow and the liver. Photosensitivity (indicated below with the following symbols as either blistering* or nonblistering) and/or (indicated below with the following symbol as) neurovisceral symptoms may be part of the porphyria phenotype. Therefore, porphyrias are classified as erythropoietic or hepatic and as cutaneous or acute.

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Table Graphic Jump Location
TABLE 28–1HUMAN PORPHYRIAS: SPECIFIC ENZYMES AFFECTED BY MUTATIONS, MODES OF INHERITANCE, CLASSIFICATION, AND MAJOR CLINICAL FEATURES OF EACH OF THE HUMAN PORPHYRIAS
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Erythropoietic Porphyrias

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  • Principal site of initial accumulation of pathway intermediates: the erythroblast

  • Congenital erythropoietic porphyria (CEP)*

  • Erythropoietic protoporphyria (EPP)

  • X-linked protoporphyria (XLP)

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Hepatic Porphyrias

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  • Principal site of initial accumulation of pathway intermediates: the liver

  • δ-Aminolevulinic acid dehydratase porphyria (ADP)

  • Acute intermittent porphyria (AIP)

  • Hereditary coproporphyria (HCP)*‡

  • Variegate porphyria (VP)...

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