Heme biosynthetic pathway showing the sites of enzymatic defects in the porphyrias and the major biochemical abnormalities in biochemically active disease. Only the major increases in the urine, stool, plasma, and erythrocytes (RBCs) are shown. The dashes (—) represent no abnormalities. For several of the diseases, many patients are biochemically silent (“latent”) carriers of the enzymatic defects for most of their lives.

Abbreviations: COPRO, coproporphyrin; COPROGEN, coproporphyrinogen; ISOCOPRO, isocoproporphyrin; PROTO, protoporphyrin; URO, uroporphyrin; UROGEN, uroporphyrinogen; Zn, zinc.

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