Glossary of Terms


Abdomen:  the part of the human body between the chest and pelvis.

Abnormal: differing from normal.

Accumulation, accumulate: the build-up of a substance or the process of acquiring more.

Acquired: a condition which is not inherited from a parent and is not associated with a genetic mutation. Acquired conditions can develop at any time in life and are triggered by factors external to the patient, regardless of genetics. The majority of cases of Porphyria Cutanea Tarda are acquired.

Acute:  beginning abruptly with marked intensity or sharpness, and then subsiding after a relatively short period. As in “acute porphyria,” those porphyrias characterized by sudden attacks of intense pain and other typical symptoms, typically lasting days or weeks.

Acute attack: the phase of an acute porphyria attack which is particularly severe.

Acute Intermittent Porphyria (AIP):  an acute type of hepatic porphyria resulting from a deficiency of the enzyme, hydroxymethylbilane synthase (HMB-synthase).

ALA-Dehydratase Deficiency Porphyria (ADP):  an acute type of hepatic porphyria resulting from a deficiency of the enzyme, ALA-dehydratase.

Aminolevulinic acid dehydratase (ALA-D): the second enzyme in the heme biosynthesis pathway; its deficiency results in ALA-Dehydratase Deficiency Porphyria (ADP).

Aminolevulinic acid synthase (ALA-Synthase or ALAS):  the first enzyme in the heme biosynthesis pathway; a deficiency results in X-linked sideroblastic anemia, and a “gain of function” results in X-linked protoporphyria (XLP)

Aminolevulinic acid (ALA):  an intermediate compound in the heme biosynthesis pathway; accumulates in ADP and in the acute porphyrias during an acute attack.

Amniocytes:  cells in the amniotic fluid surrounding the fetus before birth.

Amniotic fluid: the fluid surrounding the fetus inside the uterus.

Analgesic:  a drug or medicine used to relieve pain, for example ibuprofen or acetaminophen. 

Analysis: examination to discover characteristics or meanings.

Anemia: a decrease in normal number of red blood cells (RBCs) or less than the normal quantity of hemoglobin in the blood.

Anticonvulsant:  drugs used for the prevention of seizures.  Many older anticonvulsants are very dangerous in the acute pophryias.

Antidiuretic hormone (ADH):  a product made by the hypothalamus and transported to the pituitary gland, with the major purpose of promoting reabsorption of water in the kidneys.

Antidiuretic:  a drug that helps control body water balance by reducing urination.

Assay: assessment of characteristics (as weight, measure, or quality).

Asymptomatic carrier:  a person who has inherited a gene that causes a disorder but does not show symptoms.

Attack:  an active episode of a chronic or recurrent condition.

Autonomic nervous system:  controls the smooth muscle of the internal organs and glands.

Autosomal dominant:  one of several ways that a disorder, trait, or disease can be passed down through families.  An autosomal dominant disorder means that one copy of an abnormal gene on one pair of autosomes (non-sex determining chromosomes) must be present in order for the disorder, trait, or disease to develop.  If a parent carries the abnormal gene for a specific disorder, each of his or her children have a 50% risk for also having the disease.  The acute porphyrias (AIP, HCP, and VP) and familial PCT follow this pattern of inheritance.

Autosomal recessive: one of several ways that a disorder, trait, or disease can be passed down through families.  An autosomal recessive disorder means that two copies of an abnormal gene on one pair of autosomes (non-sex determining chromosomes) must be present in order for the disorder, trait, or disease to develop.  If both parents carry the abnormal gene for a specific disorder, each of their children are at a 25% risk for having the disease.  Erythropoietic protoporphyria (EPP), congenital erythropoietic porphyria (CEP), and  ALA-Dehydratase Porphyria (ADP) follow this pattern of inheritance.

Autosomes: the 22 non-sex determining chromosomes (that is, all the chromosomes except X and Y).


Barbiturates:  act as central nervous system depressants and are used as sedatives or hypnotics. They may precipitate acute attacks.

Beta-carotene:  a yellow pigment that gives color to plants such as carrots and tomatoes. It is often used as a treatment for sun-sensitive porphyria.

Bilirubin: formed as hemoglobin breaks down; gives bile its yellow green color.

Biochemical pathways:  systems in the body for processing molecules for useful functions.

Biochemical tests:  tests based on the identification and measurement of porphyrins in samples such as, blood, urine and stool. 

Biopsy, liver:  requires a small core of liver tissue to be removed from the liver with a needle introduced between the lower ribs on the right side of the chest.

Bone marrow:  the tissue in the hollow inside of bones, responsible for making new blood cells.


Carbohydrates:  certain foods that are high in starch and a good source of energy, including breads, pastas, beans, potatoes, bran, rice, and cereals.

Carrier: an individual who has inherited a disease-causing genetic mutation for an autosomal recessive disorder; such carriers will not have symptoms of that disorder.,

Central nervous system (CNS):  made up of the spinal cord and brain; the CNS coordinates the activities of all parts of body.

Centromere: region of a chromosome found near its middle where individual chromosomes in a pair  come in contact during cell division.[NH1] 

Chloroquine:   is a drug that was developed to treat malaria, then has found to be useful also in the treatment of PCT.

Chorionic Villus Sampling (CVS): a procedure used in the first trimester of pregnancy to diagnose genetic disorders; the procedure is done by the removal of a small piece of placenta tissue (chorionic villi) from the uterus during early pregnancy to screen the baby for genetic defects.

Chromatography: a method of separating and identifying the various components of a mixture.  

Chronic (or Chronically): a situation or disease with a long duration.

Cirrhosis:  extensive scarring of the liver, which is the end result of many chronic diseases involving the liver

Coding, or encoding:  the process of using the instructions in DNA to make specific proteins.

Compensate: to make up for something that is missing.

Complex carbohydrates: a component of food, commonly known as starches; these are large molecules that take longer for our bodies to break down.

Congenital:  a condition that is present at birth, as a result of either heredity or environmental influences.

Congenital Erythropoietic Porphyria (CEP):  a cutaneous porphyria due to a marked deficiency of the enzyme, uroporphyrinogen III synthase.

Coproporphyrin:  a compound derived from coproporphyrinogen. Increased coproporphyrin levels in the urine may indicate Congenital Erythropoietic Porphyria.

Coproporphyrinogen I:  an intermediate porphyrinogen in heme biosynthesis pathway. This compound is not physiologic and cannot be metabolized further.

Coproporphyrinogen III:  an intermediate porphyrinogen compound in heme biosynthesis pathway that is metabolized in the pathway.

Coproporphyrinogen oxidase: an enzyme in the heme biosynthesis pathway; its deficiency results in autosomal dominant Hereditary Coproporphyria (HCP).

Cutaneaous:  refers or pertains to the skin, as in “cutaneous porphyria,” a porphyria whose symptoms affect primarily the skin.

Cytochromes:  heme-containing proteins involved in cellular functions requiring oxygen; cytochrome P-450 is a subgroup that is particularly abundant in the liver.

Cytoplasm:   the substance inside a cell that surrounds its nucleus.


Defect: an abnormality.

Deficiency: a lower amount of enzyme compound that is necessary for normal function.

Delta-aminolevulinic acid: see "aminolevulinic acid.”

Dialysis:  method for removing waste products such as potassium and urea, as well as free water from the blood when the kidneys are in renal failure.

Disease: deviation from a normal state of physical or mental health caused by the body’s response to the genetic defects, the environment, and/or infectious substances.

Disorder: An abnormal physical or mental condition.

DNA (deoxyribonucleic acid): a molecule that contains the genetic instructions used in the development and functioning of living organisms, including some viruses.

Dominant inheritance:  type of inheritance pattern wherein only one affected parent is needed to pass on the trait to their children. Each child of a parent who carries the trait has a 50% chance of inheriting the trait.


Elevated/Elevation: higher than normal.

Endogenous:   originating within (produced by) the body.

Enzyme:   a protein that is produced by cells and catalyzes (promotes) chemical reactions within the body.

Erythrodontia:  a reddish or reddish-brown discoloration of the teeth.

Erythrocyte:  a mature red blood cell.

Erythropoietic:  pertains to the production of red blood cells.

Erythropoietic Porphyria (EPP):  a cutaneous porphyria due to the deficient activity of the enzyme, ferrochelatase.

Estrogen:   the most important female sex hormone, along with progesterone.  Both estrogen and progesterone levels fluctuate during the menstrual cycle and change during pregnancy.  Synthetic estrogens and progesterone are used in oral contraceptives and hormone replacement therapy when used to relieve the menopause symptoms.

Exacerbate:  to make the symptoms of a disorder worse.

Excess:  an amount or quantity beyond what is needed for normal function.

Exogenous:  refers to originating outside of the body.

Exon:  a sequence of DNA in a gene that codes for the protein. Each gene has many exons (separated by introns) that together tell the cell to make a specific protein.

Extremities:  arms and legs.


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. 

Free erythrocyte protoporphyrin:  heme without iron inserted. Elevated levels may indicate Erythrpoietic Protoporphyria.

fPCT:  familial porphyria cutanea tarda, the inherited form of PCT, also known as PCT Type II..


Gender: male or female.

Gene(s):  a specific sequence of nucleotides in DNA that is located on a chromosome and that determines the expression of one or more traits by specifying the production of a specific protein in the cell.

Gene locus:  the specific place on a chromosome where a specific gene is located.

Gene mutation:  a permanent change in a gene that can be passed on to offspring.

Generic drug:  the official chemical name of a drug. There is only one generic name for each drug. Although many companies may make the same drug, each one will provide its own trade name for their drug.  It is often important to know the correct generic name for a drug as the trade name is not always used on drug lists.

Genetic:  caused by or controlled by genes.

Genetic code:  sequence of nucleotides in DNA and RNA that determines the amino acid sequence of proteins.

Genetic predisposition:  the inherited genetic pattern which may make you more susceptible to certain diseases or conditions.

Genetics:  the study of the biological heredity or inheritance.

Genotype:   determines the genetic information contained in an individual. Usually refers to determining whether a particular mutation is present or absent. Literally, the "type of gene" present.

Globin:   is the protein portion of hemoglobin.

Glucose:  an important carbohydrate that serves as a major source of energy in the body.  A special glucose solution is often given intravenously to alleviate acute porphyria attacks as well as dehydration and shock.

Glycine:  one of twenty amino acids. It participates in the first step of heme biosynthesis.

Gonadotropin-releasing hormone (GnRH) analogue:  a specific type of synthetic hormone used to control a woman’s menstrual cycle.


Hallucinations:  seeing, hearing, feeling something that is not really there while a person is awake and conscious; the incorrect perceptions of any of the senses.

Hematin:  a red to blackish-brown component formed in the decomposition or breaking down of hemoglobin.

Hemochromatosis:  an autosomal recessive, genetic disorder, which leads to the accumulation of large amounts of iron in many organs, especially in the liver.

Heme:  a porphyrin containing iron.  It is the part of hemoglobin that binds oxygen, carrying it from the lungs to the rest of the body. In the liver, heme is present in cytochromes, which also bind oxygen needed for a variety of liver functions.

Heme arginate:  a synthetic heme preparation used in the treatment of porphyria in Europe but not available in the US.

Heme biosynthesis:  the formation of heme from glycine and succinyl-CoA.

Heme biosynthesis pathway:  the series of enzyme steps involved in the formation of heme.

Heme biosynthetic cascade:  see "heme biosynthetic pathway.”

Hemin (trade name Panhematin®): A commercial form of heme, suitable for human use.

Hemodialysis:  see Dialysis.

Hemoglobin (Hb, Hgb):  a specific protein in human red blood cells that contains iron and carries oxygen to other tissues in the body.

Hemolysis:  the breakdown of the red blood cells (RBC's).

Hemolytic anemia:  anemia resulting from hemolysis in the circulation

Hemoproteins:  proteins that contain heme.

Hepatic: pertaining to the liver.

Hepatitis:  an inflammation of the liver from any cause: which include alcohol misuse, hepatitis C and B infections and hemachromatosis. 

Hepatocellular cancer:  primary liver cancer (originating in the liver).

Hepatocytes: cells in the liver.

Hepatoerythropoietic Porphyria (HEP):  the autosomal recessive form of familial Porphyria Cutanea Tarda (PCT).

Hepatomegaly:  enlargement of the liver.

Hepatosplenomegaly:  enlargement of the spleen and liver.

Hereditary Coproporphyria (HCP):  an acute porphyria due to a deficient activity of the enzyme, coproporphyrinogen oxidase.

Heredity (or inheritance): refers to the passing on of traits from generation to generation.

Heterozygous:  having two different forms (or alleles) of a particular gene.  In other words, humans have 23 pairs of chromosomes, each chromosome containing a series of genes, and each gene being a specific DNA sequence.  The two members of a pair include the same genes (termed alleles), but the two DNA sequences for a specific region may be the same or different. When they are different, the individual is said to be heterozygous for the region (gene). When they are identical, the term is homozygous.

HFE:  a human gene that codes for a protein involved in iron regulation.  A deficiency of the HFE protein causes hemochromatosis.

Hirsutism:   growth of hair in excess of what is usual for a particular location.

HIV:  human immunodeficiency virus.

Homozygous:  having the same forms (or alleles) of a particular gene.  In other words, humans have 23 pairs of chromosomes, each chromosome containing a series of genes, and each gene being a specific DNA sequence.  The two members of a pair include the same genes (termed alleles), but the two DNA sequences for a specific region may be the same or different. When they are different, the individual is said to be heterozygous for the region (gene). When they are identical, the term is homozygous.

Hydroxychloroquine: an anti-malarial drug, also used to treat porphyria cutanea tarda.

Hydroxymethylbilane:  an intermediate in the heme biosynthesis pathway.

Hydroxymethylbilane synthase (HMB-synthase):  the third enzyme in the heme biosynthesis pathway; the half normal activity of this enzyme results in Acute Intermittent Porphyria (AIP).

Hyperpigmentation:   skin darker than usual, as a result of excess melanin production. Small areas of hyperpigmentation are often seen in response to skin damage in porphyria.

Hypertrichosis:  another term for Hirsutism

Hypoglycemia: Low blood sugar.

Hyponatremia: below-normal blood sodium; can occur in acute porphyria attacks, sometimes triggering a seizure.

Hypothalamus:  a region of the brain that regulates basic processes including body temperature, hunger, thirst, fatigue, and circadian rhythm.


Inborn error of metabolism:  a genetic disorder affecting body metabolism

Incidence:  the number of new cases of a specific disease occurring during a certain period of time in a population at risk for developing that disease.

Inherit(ed):  receive(d) a characteristic from a parent by genetic transmission.

Inhibition:  the act of slowing down or preventing a chemical reaction.

Intermediates:  a product that is formed from one reaction and reacts further to make another product.

Intravenous:  given to a patient by injection into a vein.

Intron: a sequence of DNA in a gene in between the exons; these sequences may be involved in the regulation of a protein.

Investigation:  an in-depth study.

Iron: an important component of hemoglobin, involved in the transport of oxygen to tissues in the body.

Isomers: compounds of identical composition but having different 3D structures.



Karyotype: a photograph of a complete set of chromosomes, providing an estimate of number and gross appearance.

Kidney:  paired organs responsible for filtering the blood and directing certain compounds into the urine.


Latent:  an inherited change that is not detectable except by biochemical or genetic analysis but may become apparent under certain circumstances  A person with latent porphyria does not presently have symptoms, and probably will not experience symptoms unless they are somehow triggered.

Lead poisoninga 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 discovered that in most cases 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..


Manifestations:  in medicine, symptoms.

Melanin:  the pigment responsible for the colour of the skin. The more melanin that is present, the darker the skin.

Menses:  menstrual flow; the monthly flow of blood and cellular debris from the uterus that begins at puberty in women.

Menstrual cycle:  a cycle of physiological changes that lasts about 28 days and occurs in females during their childbearing years, preparing the uterus for pregnancy,

Metabolic pathway: the sequence by which the chemical changes in living cells provide energy for vital processes in the body.

Metabolites:  substances that are part of the chemical reactions within one's body.

Metoclopramide:  a medication sometimes used  to treat heartburn caused by gastroesophageal reflux.

Mitochondria:  structures found within all cells (except red blood cells), which use oxygen to produce the energy needed for cellular metabolism.

Molecule: the smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms; a group of like or different atoms held together by chemical forces.

Mutation:   an alteration in DNA that is permanent and potentially inheritable and may change the function of the gene in which it is located

Mutilation:  permanent physical injury that affects the appearance or function of any part of the body. 

Myoglobin:  the protein that carries oxygen in muscle cells.


N-acetylglutamate: a coenzyme that assists in processing the first step of the urea cycle and activates carbamoyl phosphate synthetase I.

Narcotic analgesics:  painkillers that contain an opiate and therefore may be addicting with prolonged use. Names include hydrocodone, codeine, morphine, oxycodone, meperidine (Demerol), methadone, fentanyl (Duragesic), butorphanol (Stadol) and others. They appear alone or in combination with aspirin, ibuprofen or acetaminophen. Tradenames for the compound drugs include Vicodin, Percocet, Norco, Tyco, and Oxycontin, .

Negative feedback:  when the end-product of a pathway shuts down the initiation of product formation

Nervous system:  the system of cells, tissues, and organs that regulates the body's responses to internal and external stimuli. In humans it consists of the brain, spinal cord, nerves, and ganglia.

Neuroendocrine system:  the system of cell that release hormones that affect the nervous system.

Neurological:  pertaining to the nerves and nervous system, including the disorders and diseases that affect them.

Neurotoxin:  a substance that is poisonous or damaging to the nerves.

Neurotransmission:  communication among nerve cells through signaling processes

Neurovisceral:  refers to the nerves of the internal organs.

Nitrogen: an atmospheric gas that forms many compounds in the body (such as proteins) and is a component of all living cells.

Nucleic acid:  DNA is a string of nucleotides, which contain genetic information and is in the cells of all living things and some viruses.

Nucleotides:  specific molecules that, when joined together, make up the structural units of DNA and RNA. And also play important roles in metabolism.


Offspring:  children.

Onset:  the start of, as in “the onset of symptoms”.

Organ:  a collection of tissues joined in a structure to serve a common function; for example, the lung, stomach. liver, skin, brain, kidney.

Overproduction:  to produce more than what is needed

Ovulation:  release of an egg (ovum) by the ovary; this normally occurs midway through the menstrual cycle