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  • False negative: a test result suggesting that an individual does not have porphyria when they do have the disease.
  • False positive: a test result suggesting that an individual has porphyria when they do not have the disease.
  • Fecal: pertaining to feces.
  • Feces:  stool.  It is the waste product of the human digestive system.
  • Ferritin: a protein present in the liver, which binds and stores iron. A small amount of ferritin (serum ferritin) circulates freely in the blood, where it may be measured.  A small amount of ferritin (serum ferritin) circulates freely in the blood, where it can be measured.  This increases when the liver is iron-overloaded, as in hemochromatosis, and it drops below normal in individuals who have insufficient iron.
  • Ferrochelatase: the enzyme that is the last step of the heme biosynthesis pathway; a deficiency is present in Erythropoietic Protoporphyria.
  • Fetal hydrops: a condition when there is accumulation of fluid, or edema in an unborn baby.
  • Fetus: unborn baby.
  • Fibroblasts: a cell that gives rise to connective tissue; a cell type that is grown from a skin biopsy.
  • Fibrosis: an increase of fibrous tissue or scar.
  • Fluorescence: some chemicals are capable of becoming energized by light of a particular color, then spontaneously give up the energy as light of a different color. Porphyrins are energized by ultraviolet light (400 nanometers) and release red light at 630 nm (red fluorescence). This is the basis of the tests for detecting porphyrins in urine, stool and blood.
  • Forearm: distal region of the arm, between the elbow and the wrist.
  • Formation:  the act of taking shape or form.
  • Founder mutation: one which arises in or is introduced into a relatively isolated population. Because of the isolation, people tend to marry within the population, and the founder mutation may become very common as in South Africa among the Dutch Afrikaners. 
  • fPCT: familial porphyria cutanea tarda, the inherited form of PCT, also known as PCT Type II.
  • Free erythrocyte protoporphyrin: heme without iron inserted. Elevated levels may indicate Erythrpoietic Protoporphyria.