Porphyrias, is a general term for a group of metabolic diseases that are genetic in nature. In each specific porphyria the activity of specific enzymes in the heme biosynthetic pathway is defective and leads to accumulation of pathway intermediates. Phenotypically, each disease leads to either neurologic and/or photocutaneous symptoms based on the metabolic intermediate that accumulates. In each porphyria the distinct patterns of these substances in plasma, erythrocytes, urine and feces are the basis for diagnostically defining the metabolic defect underlying the clinical observations. Porphyrias may also be classified as either erythropoietic or hepatic, depending on the principal site of accumulation of pathway intermediates. The erythropoietic porphyrias are congenital erythropoietic porphyria (CEP), and erythropoietic protoporphyria (EPP). The acute hepatic porphyrias include ALA dehydratase deficiency porphyria, acute intermittent porphyria (AIP), hereditary coproporphyria (HCP) and variegate porphyria (VP). Porphyria cutanea tarda (PCT) is the only porphyria that has both genetic and/or environmental factors that lead to reduced activity of uroporphyrinogen decarboxylase in the liver. Each of the 8 enzymes in the heme biosynthetic pathway have been associated with a specific porphyria (Table 1). Mutations affecting the erythroid form of ALA synthase (ALAS2) are most commonly associated with X-linked sideroblastic anemia, however, gain-of-function mutations of ALAS2 have also been associated with a variant form of EPP. This overview does not describe the full clinical spectrum of the porphyrias, but is meant to be an overview of the biochemical steps that are required to make heme in both erythroid and non-erythroid cells.

中文翻译：

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血红素的生物合成和卟啉症。

卟啉症是一组遗传性代谢疾病的总称。在每个特定的卟啉症中，血红素生物合成途径中特定酶的活性是有缺陷的，并导致途径中间体的积累。从表型上讲，每种疾病都会基于累积的代谢中间体而导致神经系统和/或光皮肤症状。在每个卟啉症中，血浆，红细胞，尿液和粪便中这些物质的不同模式是诊断确定临床观察结果的代谢缺陷的基础。卟啉也可以归类为促红细胞生成的或肝脏的，这取决于途径中间体的积累的主要部位。促红细胞性卟啉症是先天性促红细胞性卟啉症（CEP）和促红细胞性原卟啉症（EPP）。急性肝卟啉症包括ALA脱水酶缺乏症卟啉症，急性间歇性卟啉症（AIP），遗传性结肠卟啉症（HCP）和杂色卟啉症（VP）。皮肤卟啉卟啉菌（PCT）是唯一具有遗传和/或环境因素的卟啉菌，可导致肝脏中尿卟啉原脱羧酶活性降低。血红素生物合成途径中的8种酶中的每一种都与特定的卟啉症有关（表1）。影响ALA合酶（ALAS2）的类胡萝卜素形式的突变最常见与X连锁的铁粒幼细胞性贫血有关，但是，ALAS2的功能获得性突变也与EPP的变异形式有关。本概述未描述卟啉症的完整临床范围，