Medical Glossary

For more in-depth information or additional definitions, please link to the National Library of Medicine.

 

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Amniocentesis
a method of prenatal diagnosis at 15 weeks in which a fluid sample is removed from the womb and grown in tissue culture; it takes another 2-3 weeks for results; a fetus can be tested for genetic diseases this way

Ankle Foot Orthosis (AFO)
an apparatus used to support, align, prevent, or correct deformities or to improve the function of the ankle and foot.

Anticipation
the tendency in certain genetic disorders-like myotonic dystrophy-for individuals in successive generations to present with symptoms at an earlier age and/or with more severe manifesations; often observed in disorders resulting from the expression of a trinucleotide repeat mutation that tends to increase in size and have a more significant effect when passed from one generation to the next.

Anticholinesterases
(example: Neostigmine) one of the drugs that myotonic dystrophy patients should avoid; can adversely affect diameter of blood vessels, function of the intestines, and part of the nervous system that controls smooth muscle, heart muscle and gland cells

Apnea 
periodic absence of breathing while sleeping

Armodafinil

A drug used to treat excessive daytime sleepiness (brand name is Nuvigil)

Arrhythmia
an irregular heart beat

Aspiration pneumonia
serious form of pneumonia resulting from inhalation of foreign material, usually food particles or vomit, into the bronchi

Asymptomatic
without symptoms, at least in the mind of the person himself

Atrial fibrillation 
abnormal heartbeat in which the normal rhythmical contractions of the upper chambers of the heart (cardiac atria) are replaced by rapid irregular twitchings of the muscular wall

Attention Deficit Hyperactivity Disorder
a behavior disorder originating in childhood in which the essential features are signs of developmentally inappropriate inattention, impulsivity and hyperactivity.  Although most individuals have symptoms of both inattention and hyperactivity-impulsivity, one or the other pattern may be predominant.  The disorder is more frequent in males than females.  Onset is in childhood.  Symptoms often attenuate during late adolesence, although a minority experiences the full complement of symptoms into mid-adulthood.

Autosomal dominant
a pattern of inheritance in which if one parent has a mutated gene, each offspring has a 50% chance of inheriting it

Barium swallow test 
a test in which a patient swallows a thick white substance and the swallowing process is filmed to detect possible abnormalities

Blepheroplasty
any operation for the correction of a defect in the eyelids

Bradyarrhythmia
any disturbance of the heart's rhythm resulting in a rate of under 60 beats per minute

Bulbar weakness
presence of weakness in the tongue, lips, palate, pharynx and larynx

Cataracts
a film that can form in the eye and cause complete or partial opacity of the ocular lens, or blurry vision; in myotonic dystrophy patients, often posterior subcapsular iridescent cataracts form; they are sometimes referred to as Christmas-tree cataracts

Cardiac conduction
the electrical impulses that cause the heart to beat

Cardiomyopathy
damage to the heart muscle that decreases its ability to pump blood effectively

Cardiotoxicity 
substance that is harmful to the heart

CCTG
the abbreviation for “cytosine, cytosine, thymidine, guanine”, the chemicals in the DNA that cause myotonic dystrophy type-2 (on chromosome 3) when they are created in repeats greater than the normal number

Chorionic villus sampling (CVS)
a method of prenatal diagnosis at around 10 weeks into the pregnancy; a biopsy in which a piece of membrane around the embryo is removed using a needle through the abdomen or vagina; results in 1-2 weeks

Chromosome
one of the bodies (normally 23 pairs) located in the nucleus of a cell that hosts the genes

Cisapride 
(example: propulsid) a prokinetic drug that should be avoided by individuals with myotonic dystrophy

Club foot
an inversion of the foot in which only the outer side of the sole touches the ground; also called talipes equinovarus

CNS 
abbreviaton for central nervous system; brain

Cognitive problems
difficulties with thinking, learning and memory

Conduction defects
problems with the electrical impulses that regulate the heart beat

Congenital
present at birth

Contractures 
permanent tightening of muscles causing abnormal joint rigidity

CPAP
acronym for continuous positive airway pressure; a device that delivers air to the nose for easier breathing; often used at night for those with sleep apnea

Creatine Kinase (CK) levels
an important enzyme in muscle contraction

CTG
the abbreviation for “cytosine, thymidine, guanine”, the 3 chemicals in the DNA that cause myotonic dystrophy type-1 (on chromosome 19) when they sputter beyond the normal 5-37 repeats found along the rung-looking parts in the double helix that resembles a gracefully twisted ladder

Degenerative
deteriorating, getting worse

Depolarizing neuromuscular blocking agents 
(example: suxamethonium) drugs causing skeletal muscle paralysis

Distal
situated away from the trunk of the body, at the end of the limbs toward the feet and hands

DM1
the abbreviation for the Latin name for myotonic dystrophy (dystrophia myotonica) type 1, the more severe form of myotonic dystrophy with the mutation found on chromosome 19

DM2
the abbreviation for the Latin name for myotonic dystrophy (dystrophia myotonica) type 2, with the mutation found on chromosome 3

DMPK
the abbreviation for the myotonic dystrophy gene, the Myotonic Dystrophy Protein Kinase gene that causes DM1; it is located on chromosome 19

Double helix
two strands of DNA held together by hydrogen bonds; when enlarged it resembles a tiny ladder (with many rungs) that has been gracefully twisted; it is along these rungs that the chemical repeats stutter beyond their normal number and cause the mutation, or change, in the gene that causes myotonic dystrophy

Dominant inheritance 
as in myotonic dystrophy, the expression of a gene where if one parent carries the mutated gene, the children have a 50% chance of getting it

Dysphagia
difficulty swallowing

Dysphasia
difficulty speaking

Dyspnea
shortness of breath

Dystrophy
an inherited muscle disorder in which the muscles become weaker

Ectopic 
occuring in the wrong place in the body, such as the development of an impregnated egg outside the cavity of the uterus; or, a cardiac beat originating elsewhere other than at the sinoatrial node

EDS
acronym for excessive daytime sleepiness

EKG or ECG
electrocardiogram, a test that prints out a graphic record of a person’s heart beat

Endocrine system
the body system that secretes hormones that allow the body perform many of its functions

Epidemiology
the study of the distribution of health-related states (for a specific disease, like myotonic dystrophy) or events in specified populations

Esophagus 
the portion of the digestive canal between the pharynx and stomach

Expansion 
on FAQ's page, referring to enlargement of the myotonic dystrophy genetic mutation, or abnormality, as it passes to offspring; also refers to the enlargement of mutations within a given organ or system over the life of an affected individual (see somatic mosaicism); happens often in myotonic dystrophy

Foot drop
partial or total inability to dorsiflex (turn upward) the foot

Gait
manner of walking

Gastroenterologist 
a doctor focusing on the function and disorders of the stomach, intestines and assorted organs that are often referred to as the GI tract

Gene
a functional unit of heredity (like eye and hair color, height, among many other characteristics including inherited diseases) that occupies a specific place on a chromosome; it is capable of reproducing itself at each cell division and directs the formation of an enzyme or protein

Genetic
of or pertaining to genes; inherited

Genetic counseling
a meeting with a medical professional, often a geneticist, to learn how a possible inherited disease can affect you, and how you can choose to avoid passing it to your offspring if you so choose

Genomic background
referring to the complete set of genes inherited from one's parents

Genotypes
the sum total of the genetic material transmitted from a person's parents

GI tract
bodily system referrring to the stomach, intestines and related organs

Gonadal (or testicular) atrophy in men 
a medical condition in which the male reproductive organs (the testes) diminish in size and fail to function

G-Tube 
implanted feeding tube to supply sustenance when person is unable to safely swallow on his own impotence

Haplotype analylsis
molecular genetic testing to identify a set of closely linked segments of DNA

Heterotropia
inability of one eye to attain binocular vision with the other because of imbalance of the muscles of the eyeball--called also strabismus, squint.

Hydramnios
excessive amniotic fluid build-up during pregnancy

Hyperkalemia 
a greater than normal concentration of potassium ions in the circulating blood

Hyperostosis
excessive growth of bony tissue

Hypersomnia
excessive daytime sleepiness

Hypertrophy
general increase in bulk or a part of an organ

Hypothermia
a body temperature significantly below 98.6

Hypotonia
low muscle tone causing floppiness, as in a child with the congenital form of myotonic dystrophy

Implanted Cardioconverter Defibrillator (ICD)
a cardiac device implanted in the chest; a combination pace-maker and defibrillator designed to regulate the heart beat, to keep it from beating too fast or too slow

Impulse inhibition
the inability to control one’s impulses

In vitro fertilization
eggs are obtained from the female after her ovaries have been stimulated with infertility drugs. While under sedation and with the use of ultrasound guidance, a needle is inserted into the ovaries and eggs are aspirated. These eggs are then fertilized in the laboratory (in-vitro) with the partner's sperm and the developing embryos are cultured from three to six days.

Incentive spirometry
a breathing device to help exercise breathing muscles and help maximize lung capacity

Induction drugs
drugs used to "knock a patient out" prior to surgery and certain other procedures

Insulin resistance
diminished effectiveness of insulin in lowering blood sugar levels

Intercostal muscles
muscles between the ribs

Intubation
the insertion of a tube into the lungs to provide pulmonary ventilation, or to assist with breathing

Mexiletine
A drug used to treat myotonia (delayed muscle relaxation after contraction) in muscle diseases such as myotonic dystrophy and myotonia congenital (brand name is Mexitil)

Modafinil
A drug is used to treat excessive daytime sleepiness (brand name is Provigil)

Motility 
the power of spontaneous movement

Multisystemic disorder
a disease that can affect many different organs and systems in the body

Mutation
as used on this website, a change in the normal chemistry of a gene

Myotonia
the inability of contracted muscles to relax on command; or, a special kind of muscle stiffness

Myopathy
muscle weakness

NICU
neonatal (new born) intensive care unit

Opiates
any preparation or derivative of opium

Oro
referring to the mouth

Oropharyngeal muscle weakness 
reduced strength in the upper expanded portion of the digestive tube, between the esophagus below the mouth and nasal cavities above and in front

PCR - polymerase chain reaction
a procedure that produces millions of copies of a short segment of DNA; the amplified product, doubled each cycle for 30 more cycles, can then be subjected to further testing; it is a common procedure in molecular genetic testing in order to generate enough DNA to perform the test; in individuals suspected of having myotonic dystrophy, it can be used to determine the number of trinucleptide repeats in the DMPK gene on the 19th chromosome.

PGD
abbreviation for preimplantation genetic diagnosis achieved through in vitro fertilization where analysis of embryos is done prior to being implanted by a doctor into the uterus of a woman

Pacemaker
an implanted heart device to correct a very slow or irregular heart beat

Perioperative
around the time of surgery

Pharynx
the upper expanded portion of the digestive tube, between the esophagus below the mouth and nasal cavities above and in front

Phenotype
the observable signs, symptoms and other aspects of a person's outward appearance and behavior

PICU
Pediatric intensive care unit

Pilomatrixoma
benign skin tumors under the skin; associated with hair follicles

Placenta
organ formed inside the lining of the womb that provides nourishment for fetus and elimination of its waste products

Placenta accreta
condition in pregnancy in which the placenta (see definition) has an abnormally deep attachment through the endometrium and into the myometrium (the middle layer of the uterine wall), causing full or partial placental retention. Condition typically requires surgery to prevent abnormal post-partum bleeding and fully remove the placenta. In severe cases can lead to a hysterectomy or can be fatal. 

Placenta previa
condition in pregnancy in which the placenta (see definition) is implanted in lower segment of womb close to the internal opening of the cervix, or sometimes completely covering that internal opening

Polyhydramnios
excessive amniotic fluid build-up during pregnancy

Postoperative apnea
absence of breathing after surgery

Postpartum hemorrhage
heavy bleeding from the birth canal after vaginal delivery of a baby

Pre-mutation
the presence of slightly more than the normal number of nucleotide repeats in the genetic mutation, e.g. in DM1, somewhere between 38 and 50; CTG repeats; the person exhibits no symptoms but are at risk of having affected children

Prenatal diagnosis
a process of determining whether a child in the womb has a specific inherited disorder

Prognosis 
forecast of the probable course and outcome of a disease

PROMM 
abbreviation for proximal myotonic myopathy or DM2

Proximal
in medicine, it refers to a part of the body that is nearest to the trunk of the body, such as thighs and upper arms

Ptosis
droopy eye-lids due to muscle atrophy

Pulse oximetry
a test to measure oxygen levels in the blood

Respiratory function test
a test that measures the amount of air a person can blow out

Smooth muscles
muscles that are part of or surround internal organs, as along the gastrointestinal tract

Somatic
physical

Somatic mosaicism
in DM1, the presence of different numbers of CTG repeats (the abnormality) found in different organs and systems within the same person; in DM2, the presence of different numbers of CCTG repeats found in different organs and systems within the same person

Sonogram
an image created by ultrasound obtained by a computerized instrument; it can reveal internal parts of the body, such as thyroid gland or fetus in utero

Steinert’s disease
the first name given to myotonic dystrophy when it was identified as a disease by Dr. Hans Steinert of Germany in 1909

Strabismus
inability of one eye to attain binocular vision with the other because of imbalance of the muscles of the eyeball--called also heterotropia, squint.

Sudden heart block
a condition of the heart in which the passage of an electrical impulse is arrested, wholly or in part, temporarily or permanently

Tachyarrhythmia
very rapid heart beats

Talipes equinovarus
an inversion of the foot in which only the outer side of the sole touches the ground; also called club foot

Testicular (or gonadal) atrophy 
Condition in men in which the reproductive organs (testes) shrink and may lose function

Tetranucleotide repeats
as related to myotonic dystrophy, the series of 4 chemicals (abbreviated CCTG and found in the DNA of the ZNF9 gene, on the 3rd chromosome) that repeats itself more times than normal and causes myotonic dystrophy type 2

Tracheotomy
the implantation of a tube into the trachea to assist patient with breathing; inserted through neck just below the thyroid gland

Trinucleotide repeats
as related to myotonic dystrophy, the series of 3 chemicals (abbreviated CTG and found in the DNA of the DMPK gene, on the 19th chromosome) that repeats itself more times than normal and causes myotonic dystrophy type 1

ZNF9
the mutated gene on chromosome 3 that causes DM2; sometimes called the zinc finger gene

For a print-ready version of this information click here or go to pages 26-32 of the MDF Toolkit.