|
A |
|
Alanine aminotransferase (ALT) |
ALT
is found in blood serum and in certain body tissues, especially
hepatic tissues. It is released into the bloodstream by injury
or disease affecting the liver (see SGPT). |
|
Alleles |
Alternate forms or varieties of a gene. Alleles for a trait
occupy the same locus or position on homologous chromosomes and
thus govern the same trait. |
|
Amenorrhea |
Absence or abnormal stoppage of menstruation; also called amenia. |
|
Anemia |
Iron deficiency leading to decreased red blood cell levels and
insufficient amounts of hemoglobin and myoglobin, resulting in
weakness, fatigue, susceptibility to infection, and paleness. |
|
Arrhythmia |
Any variation from the normal heart beat rhythm, including sinus
premature beat, heart block, atrial fibrillation, atrial
flutter, and paroxysmal tachycardia. |
|
Arthralgia |
Joint pain. |
|
Arthropathy |
Any joint disease. |
|
Aspartate aminotransferase (AST) |
A hepatic enzyme released into the blood when certain organs or
tissues, particularly the liver and heart, are injured. AST is
also known as serum glutamic oxaloacetic transaminase (SGOT). |
|
Autosome |
Any chromosome other than a sex chromosome. Humans have 22 pairs
of autosomal chromosomes; and the HFE gene is on autosomal
chromosome 6. |
|
C |
back to top |
|
C282Y mutation |
A missense mutation that causes the amino acid tyrosine to
replace a cysteine at position 282 in the HFE protein, which
normally helps regulate iron uptake. This causes the HFE protein
to misfold and malfunction, which can lead to increased iron
absorption. About 5 of every 1,000 Americans of European dissent
are homozygotes for this mutation.
|
|
Cardiomyopathy |
General diagnostic term designating primary myocardial disease
that may lead to chronic heart disease. |
|
Carrier |
An individual who has one copy of a mutant allele that causes
disease only when two copies are present. Although the
associated disease does not affect carriers, two carriers can
produce a child who has the disease. |
|
Chelation therapy |
The use of a ring-shaped compound, or iron-chelating agent,
capable of forming complexes with circulating iron and assisting
in its removal from the body (see deferoxamine). |
|
Chromosome |
A threadlike package of genes and other DNA in the cell nucleus.
Humans have 23 pairs of chromosomes; 44 autosomes, and 2 sex
chromosomes. Children get half their chromosomes from the mother
and half from the father. |
|
Cirrhosis |
Cirrhosis is a disease characterized by scarring of the liver,
causing fibrosis and nodular regeneration. Destruction of normal
liver architecture prevents the liver from properly digesting
food, metabolizing drugs, or making proteins. Cirrhosis is a
serious condition. |
|
D |
back to top |
|
Deferoxamine (desferal Rx) |
Iron-chelating agent used therapeutically to treat acute iron
intoxication or chronic iron overload in transfusion-dependent
patients. May also be used to treat hemochromatosis in patients
such as anemics who cannot tolerate phlebotomy. It forms a
water-soluble complex with iron that is excreted in urine and
feces (see chelation therapy). |
|
Diabetes mellitus type I |
The islets of Langerhans are destroyed as a consequence of
genetic susceptibility, followed by the onset of autoimmune
destruction triggered by an environmental factor such as a viral
infection. The number and size of insulin-producing cells in the
pancreas are eventually reduced, leading to decreased insulin
production and glucose intolerance. |
|
Diabetes mellitus type II |
A chronic disease that results when the body's insulin does not
effectively move glucose from the blood to the interior of
cells. Excess glucose builds up in the blood and is removed by
the kidneys, resulting in excessive thirst, frequent urination,
hunger, fatigue, weight loss, and increased insulin production. |
|
Diagnostic test |
Blood testing used when a specific disease is suspected, to
verify the disease’s presence and severity (see TS and SF). |
|
E |
back to top |
|
Erythropoiesis |
The production of erythrocytes, or red blood cells. |
|
F |
back to top |
|
Fasting blood draw |
For a fasting blood draw, avoid the following items 24 hours
prior to blood draw: vitamin C, nutritional supplements,
medicinal iron or estrogen preparations, iron-containing
placebos of some oral contraceptives, and alcohol. |
|
Ferritin |
Iron-storage protein (see serum ferritin). |
|
Free radicals |
Highly reactive molecules with unsatisfied electron valence
pairs, capable of causing tissue damage and enhancing
the effects of aging. Elevated iron levels are thought to increase the
occurrence of free radical formation in the body. |
|
G |
back to top |
|
Genetic screening |
Testing of a population group to identify a subset of
individuals who carry a genetic mutation (H63D, C282Y) and are
consequently at higher risk for having or transmitting a
specific genetic disorder. Patients should receive counseling
before undergoing genetic screening. |
|
Genotype |
The genetic identity of an individual that does not contribute
to outward characteristics. Genetic makeup. |
|
H |
back to top |
|
H63D mutation |
A missense mutation that causes the amino acid aspartate to
replace a histidine at position 63 in the HFE protein, which can
lead to primary iron overload. H63D has an allele frequency of
approximately 16% in the U.S. general population. |
|
Hematocrit |
The percentage of packed red blood cells found in a unit volume
of blood. Normal levels are 35%-45% for females and 40%-50% for
males. |
|
Heme iron |
The iron found in the hemoglobin and myoglobin of foods such as
meat, poultry, and fish. It is 2-3 times more absorbable than
nonheme iron. |
|
Hemochromatosis |
The disease that occurs as a result of significant iron
overload. Hemochromatosis can have genetic and nongenetic
causes. |
|
Hemoglobin |
The protein that gives red blood cells their color; about 75% of
the body’s iron is bound to hemoglobin and involved in oxygen
transport from the lungs to the rest of the body. Regular levels
are approximately 16 g/dL for men and 14 g/dL for women. |
|
Hemolytic anemia |
Anemia caused by the destruction of red blood cells by a disease
process. Occurs in newborns as a result of blood- group
incompatibility between mother and baby. It is also caused by
abnormal red cell membranes or abnormal hemoglobin, i.e., sickle
cell anemia and thallassemia. Complications include all the ill
effects of profound anemia as well as possible problems caused
by jaundice. |
|
Hemosiderin |
An iron-containing pigment formed when the potential to store
iron as ferritin is exceeded; a type of storage iron. |
|
Hemosiderosis |
Excessive iron accumulation due to transfusion, medication,
dietary overload, and other reasons. May produce the same
pathologic changes as hereditary hemochromatosis. |
|
Hepatic biopsy |
Removal of a small piece of liver tissue for microscopic
examination or testing. A liver biopsy can be used to confirm
the hemochromatosis diagnosis by assessing the amount of iron
per gram in liver tissue. |
|
Hepatic enzymes |
Various enzymes (ALT, SGPT, AST, SGOT, and GGT) that leak into
the bloodstream as a result of injury to liver cells from
infection, iron overload, or bile flow obstruction. Elevated
enzymes are suggestive of liver damage. |
|
Hepatic iron concentration |
The amount of iron in the liver. Measured by atomic absorption
spectrophotometry of hepatic parenchymal cells or histologically
with Perl’s stain. Normal values are <80 mol/g dry weight; >80
mol/g indicates overload. |
|
Hepatitis |
Inflammation of the liver. |
|
Hepatocellular carcinoma |
A malignant growth made up of liver epithelial cells that tend
to infiltrate the surrounding tissues and give rise to
metastases. Liver cancer. |
|
Hepatomegaly |
Enlargement of the liver. |
|
Hereditary hemochromatosis |
The genetic disease that results from significant iron overload.
The majority of hereditary hemochromatosis (also known as Type I
Hemochromatosis) is associated with homozygous mutations in the
HFE gene. There are other heritable forms, presumably associated
with other genes. |
|
Heterozygous |
Possessing two different forms (alleles) of a particular gene,
one inherited from each parent, e.g. C2824/H63D. |
|
HFE gene |
The gene-encoding translation of the HFE protein, which plays a
roll in iron absorption. Mutations of this gene can predispose
to developing primary iron overload. An estimated 10% of the
U.S. population carries an HFE gene mutation. |
|
HFE gene mutations |
The HFE gene protein product is a transmembrane glycoprotein
that modulates iron uptake. Mutations in this gene compromise
its function and can lead to iron overloading. |
|
HFE protein |
An HLA-like protein that is expressed on the surface of duodenal
crypt enterocytes and participates in iron uptake and transport.
Mutations in this gene appear to cause these cells to lose the
ability to sense the level of body iron stores. |
|
Homozygous |
Possessing two identical forms (alleles) of a particular gene,
one inherited from each parent. Individuals who are homozygous
for a trait are referred to as homozygotes, e.g. C2824/C2824. |
|
Hyperferremia |
High levels of serum iron caused by random iron overload
(repeated transfusions, primary hemochromatosis), liver disease,
disordered or decreased erythropoiesis, or hemolytic anemia. |
|
Hyperthyroidism |
Overactive thyroid. |
|
Hypotension |
Abnormally low blood pressure. |
|
Hypothyroidism |
Underactive thyroid. |
|
Hypovolemia |
Abnormally decreased volume of blood circulating in the body. |
|
I |
back to top |
|
Iron overload |
The accumulation of excess iron in body tissues. Iron overload
usually occurs as a result of a genetic predisposition to absorb
iron in excess of normal.
Iron overload can also occur as a complication of:
- Other hematologic disorders, e.g., inherited and acquired
anemias.
- Chronic transfusion therapy or repeated injections of iron
dextram.
- Chronic hepatitis.
- Excessive iron ingestion.
|
|
J |
back to top |
|
Juvenile hemochromatosis |
Non-HFE hemochromatosis in a person younger than age
30. Also known as Hemochromatosis Type 2A or 2B (see Heritable
and Acquired Disorders Associated with Iron Overload.) |
|
M |
back to top |
|
Missense mutation |
A nucleotide substitution within a gene that changes a codon so
that it codes for a different amino acid in the protein. This
usually changes the activity of the protein. |
|
N |
back to top |
|
Neoplasm |
Any new and abnormal tissue growth. |
|
Non-alcoholic steatohepatitis (NASH) |
A liver that contains fatty deposits and shows evidence of
inflammation but has not been damaged by alcohol. |
|
Nonheme iron |
The iron in plant-based and iron-fortified foods. |
|
P |
back to top |
|
Penetrance |
The proportion of individuals with a specific genotype who
manifest the genotype at the phenotype level. In other words,
those carrying a gene that also outwardly express traits for
that gene. |
|
Phenotype |
Manifestation of a genetic trait as a clinically observable sign
or symptom. |
|
Phlebotomy |
To puncture a vein for the purpose of withdrawing blood. The
preferred treatment for those suffering from hemochromatosis. |
|
Porphyria cutanea tarda |
Disorder of heme biosynthesis due to a defective liver enzyme (uroporphyrinogen
decarboxylase). Symptoms include photosensitivity; hepatic
dysfunction; discolored teeth, gums and skin; excessive hair;
and psychiatric symptoms that result from porphyrin accumulation
in the blood. |
|
Prevalence |
The percentage of cases of a disease in a population at a given
time. |
|
R |
back to top |
|
Recessive trait |
A genetic disorder that appears only in patients who have two
copies of a mutant allele, one from each parent. An individual
who has one copy of the mutant allele is a carrier. |
|
S |
back to top |
|
S65C mutation |
A missense mutation that causes a cysteine to replace a serine
at nucleotide position 193. The mutation is in a region
implicated in binding the transferrin receptor to the HFE
protein, and has a modest effect on iron metabolism. S65C has an
allele frequency of 1.5% in the general population. |
|
Secondary hemochromatosis |
Acquired forms of hemochromatosis. Caused by various anemias,
chronic transfusion therapy, or other nongenetic conditions. |
|
Serum |
Blood serum is the noncellular clear liquid that separates from
blood on clotting. Serum is equivalent to plasma without
plasma’s clotting elements. |
|
Serum ferritin test (SF) |
Determines serum ferritin levels. The body increases production
of serum ferritin when excess iron is absorbed. Normal levels
are <200 ng/ml for premenopausal females, <300 for males and
postmenopausal females. |
|
Serum glutamic- oxaloacetic transaminase (SGOT) |
A hepatic enzyme detected in blood tests and used in cases of
suspected coronary occlusive heart disease, or liver diseases
such as hepatitis or cirrhosis. A 2 to 3-fold increase in SGOT
is found in 50-60% of patients with HHC (see AST). |
|
Serum glutamic pyruvic transaminase (SGPT) |
An enzyme released into the bloodstream due to injury or disease
affecting the liver: it is found mainly in blood serum and
hepatic tissues. SGPT levels are checked for suspected liver
disease and mononucleosis, or to monitor the effect of long-term
drug therapy on the liver (see ALT). |
|
Sideroblastic anemia |
Term used to describe a group of rare blood disorders
characterized by the bone marrow's inability to manufacture
normal red blood cells. |
|
T |
back to top |
|
Tachycardia |
Excessive rapidity in the action of the heart; the term is
usually applied to a heart rate above 100 beats per minute. |
|
Thalassemia |
An inherited hemoglobin synthesis disorder resulting in reduced
globin chain synthesis and chronic hemolytic anemia. Treating
anemia by chronic transfusion therapy predisposes to secondary
hemochromatosis. |
|
Therapeutic phlebotomy |
A procedure in which a unit of blood is collected via
venipuncture to treat a condition such as iron overload. |
|
Total iron binding capacity (TIBC) |
Measurement of the maximum iron concentration that transferrin
can bind. Increased TIBC levels may indicate iron-deficiency
anemia; decreased TIBC may indicate cirrhosis (TIBC = UIBC +
serum iron). |
|
Transaminase |
One of the aminotransferase enzymes, which catalyze the transfer
of an amino group from an alpha-amino acid to an alpha-keto
acid. |
|
Transferrin |
A protein synthesized in the liver that transports iron in the
blood to red blood cells for use in heme synthesis. |
|
Transferrin receptor, TfR |
A transmembrane disulfide-linked dimer of identical 85-kDa
polypeptides mediating iron uptake. The amount of transferrin
receptor expressed on a cell is proportional to the cell's need
for iron. Since the majority of metabolic iron is used for
hemoglobin synthesis, 80% of total TfR is on erythroid precursor
cells. |
|
Transferrin saturation test (TS) |
Proportion of transferrin proteins that are carrying iron.
Normal range is 16%-45% in a fasting TS. Elevated TS indicates
iron overloading.(serum iron [SI] / TIBC x 100) or (SI / SI +
UIBC x 100). |
|
U |
back to top |
|
Unsaturated iron binding capacity (UIBC) |
About one third of transferrin iron-binding sites are occupied
by iron; therefore, serum has considerable reserve iron-binding
capacity. This is called serum unsaturated iron binding capacity
(UIBC) (see TIBC). |
|
V |
back to top |
|
Vibrio vulnificus |
A microbe that causes food-poisoning-like symptoms. |
|
W |
back to top |
|
Wild type |
In genetics, the standard phenotype for any organism, or a gene
that determines a standard phenotypic trait. |
