text: The following genes are part of the chemical pathway for making heme:
  *ALAD: aminolevulinic acid, δ-, dehydratase (deficiency causes ala-dehydratase deficiency porphyria)
  *ALAS1: aminolevulinate, δ-, synthase 1
  *ALAS2: aminolevulinate, δ-, synthase 2 (deficiency causes sideroblastic/hypochromic anemia)
  *CPOX: coproporphyrinogen oxidase (deficiency causes hereditary coproporphyria)
  *FECH: ferrochelatase (deficiency causes erythropoietic protoporphyria)
  *HMBS: hydroxymethylbilane synthase (deficiency causes acute intermittent porphyria)
  *PPOX: protoporphyrinogen oxidase (deficiency causes variegate porphyria)
  *UROD: uroporphyrinogen decarboxylase (deficiency causes porphyria cutanea tarda)
  *UROS: uroporphyrinogen III synthase (deficiency causes congenital erythropoietic porphyria)