Glossary of Terms

Glossary of terms


Abnormal Any change from the average, not necessarily harmful. When used in reference to genes, an abnormal gene might result in a specific disorder.

Aetiology (etiology) The cause or causes of a disease or condition.

Alendronate A drug in the bisphosphonate family that is prescribed under the name Fosamax. It is given as a daily or weekly tablet.

Ambulation (Ambulatory) Walking or being able to walk.

Ameliorate To make or become better.

Amino Acids Small chemical building blocks of proteins that play an important role in metabolism, growth, maintenance, and repair of tissue: there are over 20 common amino acids which join in different combinations to make up proteins.

Anesthetist A health professional who is responsible for putting you or your child to sleep during operations or procedure. A health professional trained to administer anesthetics.

Audiogram A graphical chart showing the responsiveness of vibration frequency of the ear to sounds of differing pitch.

Autosome Any chromosome that is not a sex chromosome (an X or Y chromosome); the autosomes are numbered chromosomes and in humans are given the numbers 1-22. Chromosome 1 is the largest and 22 is the smallest.

Autosomal dominant A dominant gene on an autosome – exerts genetic dominance.

Autosomal recessive A recessive gene on an autosome – usually producing little or no physical effect.

Auxology The taking of measurements e.g. height, weight, head circumference etc.


Basilar impression Compression of the base of the skull which can cause neurological signs and symptoms. Also referred to as Basilar Invagination (BI). It is an upward protrusion of the top of the spine into the base of the skull. It results in neurological complications that are potentially very serious. Symptoms can include headache, double vision, imbalance and arm or leg weakness. About 50% of people with OI type III or IV have moderate or severe BI.

Biochemical Relates to the chemistry of living tissues.

Bisphosphonates (also known as pamidronate, fosamax, alendronate, etc.). Bisphosphonates are a class of drug developed for the treatment of osteoporosis. They mimic the structure of pyrophosphate, a natural occurring component of normal bone. Bisphosphonates inhibit the activity of bone cells called osteoclasts (the cells that resorb bone) to allow bone growth to occur. The different compounds each have result in slightly different characteristics and potency. These drugs include pamidronate, alendronate, and zoledronate.

Bone Density Test also called bone mineral density (BMD) tests, measure bone density in various sites of the body. It is most important to measure bone mass in the spine, hips, and arms because these areas are likely to fracture when bone mass is low. These tests are useful for people with OI as a method for estimating fracture risk and to assess the result of treatments.

Bone Mass The weight of the skeleton, overall or in specific regions such as the spine or hip.

Bone Mineral Content (BMC) Refers to the minerals that make up a bone.

Bone Mineral Density (BMD) Refers to how dense a bone is, the amount of bone per unit of skeletal area. The less dense a bone is, the more likely it is to fracture. Tests for BMD are used to evaluate bone health and fracture risk.

Bone resorption The breaking down of bone.

Bone synthesis The building up of bone material.

Brittle Teeth (Dentinogenesis Imperfecta) Hereditary condition characterised by translucent grey to yellow-brown teeth involving both deciduous (baby) and permanent teeth. The enamel fractures easily. Dentinogenesis Imperfecta can be seen in some people with osteogenesis imperfecta.


Calcitriol The active form of vitamin D. Calcitriol is formed in the kidneys or made in the laboratory. It is used as a drug to increase calcium levels in the body in order to treat skeletal and tissue-related calcium deficiencies.

Calcium A mineral essential for healthy bones, found mainly in the hard part of bones, where it is stored. Calcium is added to bones by cells called osteoblasts and is removed from bones by cells called osteoclasts.

Callus New bone laid down at the site of a fracture as part of the healing process. Some people with OI develop large calluses. Extremely large calluses at the site of fractures or bone surgery is one symptom of OI Type V.

Carbohydrate A class of organic substances containing carbon, hydrogen and oxygen. They include sugars, starches and cellulose and among other things provide the body with energy.

Cardiologist A doctor who specializes in disorders of the heart and its functions.

Caries Decay of teeth. A progressive destruction of bone or tooth.

CAT Scan  Computerised Anatomical Tomography. Refers to a widely used painless technology which assists in the diagnosis and treatment of many conditions. It is also known as computerised axial tomography (CAT) and computerised transaxial tomography (CTAT).

Carrier of a mutant gene An individual who has one normal and one recessive (i.e. abnormal) gene is said to be a carrier for a specific condition. The carriers of a recessive mutation in a gene are usually not affected but they are at risk of passing on the abnormal gene to their biological children.

Carrier screening Testing to determine if individuals are carriers for a mutant or recessive (i.e. abnormal) gene for a particular disorder.

Chromosome A thread-like structure found in the nucleus of all the body cells (except red blood cells) consisting of DNA and proteins. Each chromosome can be thought of as a string of beads where every bead represents a gene. The usual number of chromosomes in human cells is 46 consisting of 23 pairs: 22 pairs of autosomes and two sex chromosomes, the X and/or Y. The sperm and egg (ova) cells each normally contain 23 chromosomes, one of each autosome and either an X or Y chromosome.

Clinical Geneticist A health professional who has studied inherited and other genetic disorders.

CNS Abbreviation of the Central Nervous System. It refers to the brain and the spinal column in humans.

Collagen Collagen is a protein that is made up of threads, similar to those found in cotton fabric. In the bone, the spaces between the collagen fibers are filled with a hard material that will resist compression. This chalk-like material is a calcium salt called apatite. Connective tissue, cartilage and bone are all made up of collagen.

Comminuted A type of fracture in which there is splintering or fragmentation of the bone.

Complete Displaced A type of fracture when the bone fractures all the way through and the pieces of bone separate.

Complete Undisplaced A type of fracture when the bone fracture is all the way through the bone but the pieces of bone do not separate.

Compression A type of fracture which commonly occurs in the vertebrae after a jarring injury. The fracture is wedge shaped and the vertebra is compressed more at the front than the back.

ConnecTeD = A fund raising committee of the New Children’s Hospital to raise funds to support the Connective Tissue Dysplasia Clinic of the hospital.

Cortical Bone The external bone surface composed of multiple compacted layers of bone. It provides the strength of the long bone.

CRS Commonwealth Rehabilitation Service web –


Degenerative  – a deterioration of physical tissue or an organ in which its vitality is diminished or its structure impaired or in where the affective limb, tissue or organ is functionally impaired.

Deletion Mutation Occurs when part of a gene is missing. In cases of osteogenesis imperfecta, part of one of the genes for type 1 collagen has been deleted; it is missing. The resulting gene is shorter than it should be and this contributes to the genetic causes for OI.

Dental Relating to or used on the teeth.

Dentinogenesis imperfecta Dental problems experienced by people with OI. A disorder of tooth development inherited as an autosomal dominant and characterized by relatively soft enamel in both the primary and permanent teeth that makes the teeth abnormally vulnerable to fracture, abrasion, and wear.

DEXA (Dual Energy X-ray Absorptiometry) A machine which measures bone density using low dose radiation. A common method for measuring bone mass. The results of this test are usually reported as BMD or bone mineral density.

DNA (deoxyribonucleic acid) The ‘building block’ for all genetic material. The chemical compound which makes up genes within chromosomes and is the basic material of heredity. It is made up of chemicals called nucleotide bases linked together in a chain. Two chains of nucleotides twist around each other to form a double helix.

Dominant Every cell contains two copies of each gene. One gene might be mutant and the other “normal”. If the mutant gene is expressed in the cells (resulting in a particular characteristic or a disorder), the mutant gene is said to be dominant over the other “normal” copy of the gene. A disorder or characteristic caused by a dominant gene mutation only requires one of the genes to be mutated. Also see Recessive.

Dysplasia Abnormal development or growth of tissues or cells (such as organs or cells).

DOCS = Department of Community Services web –


ECG    Electrocardiogram (sometimes called an EKG) Refers to a test that measures the electrical activity of the heartbeat.

Endocrinologist A doctor who specialises in disorders related to the glands of internal secretion and their function e.g. The pancreas, thyroid, parathyroid, adrenal glands etc.

ENT Specialist A specialist in ear, nose and throat medical health issues.

Epiphyses The ends of the long bones which, during growth, are attached to the main bone by cartilage. They eventually become joined with the principal bone.


Familial A characteristic or disorder which tends to run in families.

FBC Full blood count

Fracture A break in bone or cartilage.


Gene The basic unit of heredity; a segment of DNA which contains the information for a specific characteristic or function. A gene occupies a specific site on a chromosome known as a locus.

General Surgeon A doctor who performs general operations e.g. insertion of portacath, appendix removal.

Genetic Counselling Diagnosis, information and support provided by health professionals with specialised training in genetics and counselling.

Genetic Counsellor A health professional trained in genetics and counselling, provides information and emotional support after diagnosis of a genetic condition.

Genetics The study of genes and heredity.

Genome A complete set of chromosomes found in each cell of the human body.

Genu Valgum The inward curving of the knees or knock knees.

GP General Practitioner. Also see Physician.

Greenstick An incomplete fracture of a long bone – seen mainly in children. The bone does not break all the way through.


Heredity the sum of the qualities and potentialities genetically derived from one’s ancestors or parents.

Heterozygous When the two partner chromosomes have two different forms of a gene at the same point on each chromosome. One chromosome of a pair comes from the father and the other from the mother.

Homozygous When the two partner chromosomes have two identical forms of a gene at the same point on each chromosome. One chromosome of a pair comes from the father and the other from the mother.

Hypermobility An increase in the range of movement especially a joint.

Hypocalcaemia Low levels of calcium in the blood or a deficiency of calcium in the blood.

Hypomobility A decrease in the range of movement especially a joint.


Imperfecta The Greek word for “imperfect.” The words “osteogenesis imperfecta” means bone that is imperfectly made from the beginning of life.

Inflammation A response to injury that is marked by redness, heat, pain, swelling, and often loss of function.

Infusion Administration of a drug intravenously.

Inherited The transmission of genetic information from a parent to a child.

Intramedullary Rod A thin metal device that is inserted as an internal support within the medullary canal (central space) of a long bone.

IV  Medical term used to describe and Intravenous drip


Kyphosis Exaggerated outward curvature of the spine, the convexity being towards the back, usually in the thoracic region.

Kyphoscoliosis Lateral curvature (or sideways) of the spine with vertebral rotation, associated with an anteroposterior (or forwards to backwards) hump in the spinal column.


Matrix The intercellular substance of tissue. It is the structure within connective tissue where the mineral matter attaches.

Medullary Canal The central space of a long bone.

Magnetic Resonance Imaging (MRI) Refers to a technique that uses radiofrequency waves and a strong magnetic field rather than x-rays to provide remarkably clear and detailed pictures of internal organs and tissues. An MRI can give very clear pictures of soft-tissue structures near and around bones; it is the most sensitive exam for spinal and joint problems.

MSU Midstream urine sample

Mutation A permanent change in a gene (either a physical change in chromosome relations or a biochemical change in the codons that make up genes) which is then able to be inherited. Mutations can occur naturally and spontaneously or they might be due to exposure to mutagens.


Neurologist A doctor who specialises in the diagnosis and treatment of disorders of the nervous system.

NH&MRC National Health & Medical Research Council web

Novel An unusual or non-standard form. OI Type V and Type VI are referred to as “novel forms of OI,” because they have a significant characteristic that is different from the four generally recognized types. No defect in the genes that control the body’s production of Type 1 collagen has been found in people who have been diagnosed with these types of OI. The other types of OI all are associated with defects in Type 1 collagen.


Occupational Therapist A professional who practices techniques in the rehabilitation of those with mental or physical handicaps.

OI Tarda (OI Congenita) Part of a classification system for people with OI that was in general use until the early 1980’s. OI tarda identified people who were diagnosed with OI after the newborn period. For these individuals, OI was not apparent at birth and fractures occurred later.

OI Type I (Type I OI) The most common and the mildest form of osteogenesis imperfecta (OI).

OI Type II (Type II OI) The most severe form of osteogenesis imperfecta. Infants are usually born with multiple fractures, an unusually soft skull, and an unstable neck and are quite small. Almost all infants with Type II OI die at or shortly after birth, often due to respiratory problems. In the newborn period, it can be difficult to distinguish between Type II and severe type III OI. Very rare exceptions of true Type II infants with longer survival have been reported.

OI Type III (Type III OI) A severe form of osteogenesis imperfecta that is sometimes referred to a “Progressive Deforming OI.” Common signs include short stature, fractures present at birth, progressive long bone deformities, spinal curvature and barrel-shaped rib cage.

OI Type IV (Type IV OI) Sometimes referred to as the “moderate” form of osteogenesis imperfecta. It is in between Type I and Type III in severity.

OI Type V (Type V OI) A recently identified form of osteogenesis imperfecta. It does not appear to have a collagen defect and is characterized by a dense band adjacent to the growth plate of the long bones, development of unusually large calluses at the sites of fractures or surgical procedures and calcification of the membrane between the bones of the forearm.

Ophthalmologist A doctor who specialises in the diagnosis and treatment of disorders of the eye.

Orthopaedic Surgeon A surgeon who specialises in the corrective treatment of disorders involving limbs, bones, muscles or joints. Surgeons are specialist physicians.

Orthopaedic Surgery Surgery that involves the musculoskeletal system. The most common orthopedic surgery for people with OI is rodding surgery.

Orthotics Orthopaedic appliances aimed at improving posture, function or mobility, such as braces, splints or moulded shoe inserts.

Osteoblasts Cells which produce bone. Part of the bone turnover cycle.

Osteoclasts Cells which remove and remodel bone. They are responsible for bone resorption (breakdown). Part of the bone turnover cycle.

Osteogenesis The development or formation of bone.

Osteogenesis imperfecta A genetic disorder of connective tissue characterised by bones that break easily, often from little or no apparent trauma. Osteogenesis imperfecta (OI) is a highly variable disorder with signs and symptoms ranging from mild to severe. Most people with OI have a faulty gene that instructs their bodies to make either too little type 1 collagen or poor quality type 1 collagen. Type 1 collagen is the protein “scaffolding” of bone and other connective tissues. In addition to fractures, people with OI sometimes have muscle weakness or joint laxity, easy bruising, abnormal teeth and skeletal deformities. People with OI may experience respiratory difficulties, and hearing loss. Those with the more severe forms are short in stature, while those with the milder forms will be shorter than average compared to others in their family. There are four generally recognized types of OI. OI is reported to occur with equal frequency in males and females and among all ethnic and racial groups. Two additional forms of OI have recently been identified that do not appear to have a type 1 collagen defect.

Osteopenia Reduced bone mass; decreased calcification or bone density. It is a descriptive term and does not imply a cause.

Osteopenic Too little bone formation. Bone mass is below normal and the bones are described as “thin”. This term is applied to conditions such as OI and osteoporosis.

Osteoporosis A condition in which the bones become less dense and more likely to fracture. Osteoporosis leads to unusually porous bone that is more compressible like a sponge than dense like a brick. This disorder of the skeleton weakens the bone leading to an increase in the risk of breaking bones (bone fracture). Osteoporosis

Osteosclerotic Too much bone formation.


Pamidronate A drug in the bisphosphonate family. It is given intravenously.

Pathophysiology The study of abnormal body functions or functions altered by disease.

Perspiration Some people who have OI appear to perspire more heavily than others experiencing the same room temperature.

Pes planus Flat foot.

Physician A skilled health-care professional trained and licensed to practice medicine and prescribe drugs to patients. (also see GP)

Physiotherapist A professional who treats physical disorders through manipulation, mobilization techniques and prescribing strengthening exercises and advice where appropriate.

Porta Cath A tube inserted into a major blood vessel to allow administration of a drug. It sits under the skin on the chest wall. Often called a “port”.

Prevalence A term used by epidemiologists (scientists who study diseases in populations) to describe how often a disorder occurs in a population. For genetic disorders such as OI, prevalence refers to the number of cases in a specified population at a designated time. The question, “How many people in Australia have OI?” is asking about the prevalence of OI.

Prognosis A prediction about the probable course and outcome of a disease or developmental abnormality in a patient.

Protein Substances which are major components of the body structure, essential to body function. They are made up of smaller units called amino acids.

Psychologist A professional who has studied in human behavior. A psychologist cannot prescribe drugs like physicians can.


Rehabilitation Specialist A professional who works with disabled individuals to help them reach maximum independence by working with their existing capabilities.

Research Nurse A professional who assists with research and organises patients for admission and treatment.

Recessive Usually producing little or no physical effect. If a mutant gene is not expressed in the cells, the mutant gene is said to be recessive to the other “normal” copy of the gene. An individual with this genetic constitution is said to be a “carrier” of a recessive gene mutation. For a recessive gene mutation to result in a particular characteristic or a disorder both copies of the genes must be mutated. Also see Dominant.

Rodding Internal support for the long bones by surgical insertion of a metal rod. This procedure is recommended to control repeated fractures, and to improve bone deformities that interfere with function. Different types of rods are used for different circumstances.


Sclerae The part of the eye around the colored pupil commonly referred to as “the whites of the eyes.” Some, not all, people with OI appear to have a blue, purple or gray tint to their sclera. The color may range from barely noticeable to very dark and may change with age.

Scoliosis Lateral curvature of the spine.

Sensory neural deafness Sound is conducted normally from the external ear through the tympanic membrane to the inner ear but the inner ear is not functioning in transmitting sounds normally to the brain, due to damaged nerves.

Stature Natural height of a person in an upright position.

Speech Pathologist A specialist dealing with defects of speech or language

Synthesis The process of building a complex compound from a number of simple chemical elements e.g. the production of bone.


TAD Technical Aids for the Disabled

Thoracic The part of the body that is situated between the neck and the abdomen and supported by the ribs, costal cartilages, and sternum.

Trabecular Bone The interweaving plates of bone that lie beneath the bone surface (cortical bone) and provide the internal strength of bone– particularly in the spine and hip. The spaces in between are filled with marrow.

T-Score  A statistical method of reporting the results of a bone density test. BMD is compared to two norms, “young normal” and “age-matched.” Young normal, known as your T-score, compares BMD to optimal or peak density of a 30-year old healthy adult. Fracture risk increases as BMD falls below young-normal levels. Age-matched, known as your Z-score, compares the individual’s BMD to what is expected in adults of the same age and body size.

Trabecula A complex network of intersecting microscopic structures which appear curved. It is characteristic of trabecular or cortical bone.


Ultrasound The use of sound waves for visualizing body tissues and structures. In pregnancy, structural abnormalities in the fetus can be detected.


Wormian Bones – refer to the extra bones within the skull of many OI patients. They are named after Dr Worm.


Z-Score This score compares an individual’s bone mineral density to an “age-matched” standard that takes into consideration age, and body size. Risk for fracture increases if the BMD is lower than the age appropriate standard Z-Score.

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Osteogenesis imperfecta (OI) is a genetic disorder that causes a person's bones to break easily, often from little or no apparent trauma. OI is also called "brittle bone disease." OI varies in severity from person to person, ranging from a mild type to a severe type that causes death before or shortly after birth.

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