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  • Latent: an inherited change that is not detectable except by biochemical or genetic analysis but may become apparent under certain circumstances  Also referred to as “dormant” A person with latent porphyria does not presently have symptoms, and probably will not experience symptoms unless they are somehow triggered.
  • Lead poisoning: a type of heavy metal poisoning caused by excessive exposure to lead.
  • Lesion: abnormal tissue damaged by disease or trauma.
  • Liver: a large vascular organ in the upper right side of the abdomen, just beneath the diaphragm; its functions include storage and filtration of blood, secretion of bile, conversion of sugars into glycogen for energy production, detoxification of many ingested substances including alcohol, nicotine, and poisons as well as many other functions important for the body.
  • Liver function tests: tests done on blood to determine how well the liver is working.
  • Low-expression allele: a “half-normal” copy of a gene. It was recently discovered that in the case of erythropoietic protoporphyria (EPP) a patient must inherit a mutation in the gene for EPP from one parent plus a “low-expression predisposing” alteration for producing lower-than-normal quantities of the enzyme, ferrochelatase from the other parent.