Glossary

The terms contained in this glossary were compiled from words or phrases in the OI Research Update Webcast presented at the 2002 National Conference, OI Foundation Fact Sheets, and suggestions from website visitors. It is not comprehensive or all-inclusive.

 

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Actonel
Aa drug in the bisphosphonate family. It is the tablet form of the drug risedronate. It is approved by the US FDA for the treatment of Paget's disease of bone, and osteoporosis.

Adult Rickets (Osteomalcia)
A disease characterized by soft, bendable bones and varying degrees of pain. It is can be caused by a lack of vitamin D or a kidney disorder. It can begin during pregnancy.

Alendronate
A drug in the bisphosphonate family that is prescribed under the name Fosamax. It is given as a daily or weekly tablet. It is approved by the US FDA to treat osteoporosis. It currently is in clinical trials as a treatment for OI in older children and adults. (For more information see tha "Bisphosphonate Q & A" on the fact sheet page.)

Allele
One of the two copies of each gene containing specific inheritable characteristics.

Ambulation (Ambulatory)
Walking or being able to walk.

Aredia (Aredia Treatment)
The commercial name for the bisphosphonate pamidronate. It is given intravenously in an experimental treatment protocol. (For more information see the "Bisphosphonate Q & A" on the fact sheet page.)

Autosomal
The gene for the disorder is not on a sex chromosone (X or Y), indicating that the abnormal gene can affect males or females equally.

Autosomal Dominant
Describes a genetic disorder such as OI that is caused by a gene that is not linked to a sex chromosome and that is cause by a single abnormal gene. (See autosomal and dominant.)

Basilar Impression (BI, Basilar Invagination)
Also referred to as Basilar Impression (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.

Basilar Invagination (BI, Basilar Impression)
Also referred to as Basilar Impression (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.

BI (Basilar Impression, Basilar Invagination)
Also referred to as Basilar Impression (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.

Bisphosphonates
A group of drugs that were originally developed to treat conditions such as Paget's Disease of Bone and osteoporosis. The different compounds each have slightly different characteristics and potency. These drugs are being investigated as treatments for OI. They include, pamidronate, alendronate, and zoledronate.

BMD(Bone Mineral Density)
The amount of bone per unit of skeletal area. Tests for BMD are used to evaluate bone health and fracture risk.

Bone Biopsy
The surgical removal of a sample of bone often from the hip for examination under a microscope.

Bone Density Test
Bone density tests, 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. (Formore information see the fact sheets "Bone Densitometry in Children and adults with OI," and "What people with Osteogenesis Imperfecta Need to Know About Osteoporosis.")

Bone Marrow transplant
An experimental treatment for OI and other bone disorders that involves taking bone marrow cells from a matched donor and transplanting them into the bone marrow of a young child. The hypothesis is that the cells will take hold and make bone that is improved in quality.

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

Bone Mineral Density(BMD)
The amount of bone per unit of skeletal area. Tests for BMD are used to evaluate bone health and fracture risk.

Bowing
A curve in a normally straight long bone. This can be the result of angulation from healed fractures or gradual deformation of the bone over time as a response to the forces upon it.

Brittle Teeth (Dentigenesis Imperfecta)
Hereditary condition characterized by translucent gray to yellow-brown teeth involving both dedicuous (baby) and permanent teeth. The enamel fractures easily. Dentigenesis Imperfecta can be seen in people with osteogenesis imperfecta or it can be caused by a separate inherited autosomal dominant trait.

Callus
An area of new bone. It is 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.

Cancellous Bone (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.

Cell
The basic structural unit of all living organisms. It is surrounded by a membrane and contains a nucleus which carries genetic material.

Chorionic Villus Sampling (CVS)
A technique used in prenatal diagnosis. Chorion cells which are found on the wall of the uterus (womb) are collected from the pregnant mother. They have the same origin as the fetal cells and can be analyzed to detect certain fetal abnormalities in the fetus including OI.

Chromosome
A microscopic rod-shaped structure present in the nucleus of all body cells except red blood cells. Chromosomes store genetic information (genes). Normally, humans have 23 pairsfor a total of 46 chromosomes. In each pair, one chromosome is inherited from the mother and one from the father.

Collagen
The major structural protein in the human body. Collagen forms the long fibers that are the underlying structure in connective tissue, such as cartilage, skin and bone. There are many types of collagen in the human body. Defects of type 1 collagen are known to cause OI.

Cortex
Compact bone.

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

Craniotabes
A disease characterized by areas of thinning and softening bones in the skull. It can be related to rickets, a disease caused by a lack of Vitamin D.

CVS (Chorionic Villus Sampling)
A technique used in prenatal diagnosis. Chorion cells which are found on the wall of the uterus (womb) are collected from the pregnant mother. They have the same origin as the fetal cells and can be analyzed to detect certain fetal abnormalities in the fetus including OI.

DEXA Scan (Dual Energy X-Ray Absorbitometry)
A common method for measuring bone mass. The results of this test are usually reported as BMD or bone mineral density. For additional information see the fact sheet "OI Issues: Bone Densitometry in Children and Adults."

DNA (Deoxyribonucleic Acid)
Deoxyribonucleic acid is the 'building block' for all genetic material.

Deletion Mutation
Ooccurs 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.

Dentigenesis Imperfecta (Brittle Teeth)
Hereditary condition characterized by translucent gray to yellow-brown teeth involving both dedicuous (baby) and permanent teeth. The enamel fractures easily. Dentigenesis Imperfecta can be seen in people with osteogenesis imperfecta or it can be caused by a separate inherited autosomal dominant trait.

Deoxyribonucleic Acid (DNA)
Deoxyribonucleic acid is the 'building block' for all genetic material.

Diaphoresis (Perspiration, Sweat)
Perspiration or Sweat. Some people who have OI appear to perspire more heavily than others experiencing the same room temperature.

Dominant
Term used to describe a genetic disorder such as OI that is caused by a single abnormal gene. This gene can be inherited from the mother or the father or be the result of a spontaneous mutation.

Dual Energy X-Ray Absorbitometry (DEXA Scan)
A common method for measuring bone mass. The results of this test are usually reported as BMD or bone mineral density. (For more information see the fact sheet "OI Issues: Bone Densitometry in Children and Adults.")

Dwarfism
A medical or genetic condition that results in an adult height of under 4'10".

Fos
A family of proteins that function as transcription factors. They are being studied because they induce bone formation.

Genetics
The branch of science concerned with heredity.

Genome
A complete set of chromosomes found in each cell of the human body. Chromosomes are microscopic structures composed of DNA.

Histology
The science concerned with the minute structure of cells, tissues, and organs. The study of tissue.

Histomorphology
The form and structure of an organism or any of its parts as seen through a microscope.

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

In vitro
Describes a process that occurs in an artificial environment such as a test tube.

In vivo
Describes a process that occurs in the living body.

Intramedullary Rod
A thin metal device that is inserted as an internal support within the medullary canal (central space) of a long bone. (For more information see the fact sheet "OI Issues: Rodding Surgery.")

Kyphoscoliosis (Kyphosis)
Curving forward or a hunched deformity of the spine, combined with scoliosis, a side-to-side curve of the spine.

Kyphosis (Kyphoscoliosis)
Curving forward or a hunched deformity of the spine, combined with scoliosis, a side-to-side curve of the spine.

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.

Metabolism
Chemical changes that occur in tissues.

Mosaic (Mosaicism)
A rare genetic situation when one parent has a mutation that causes a disorder to be present in a percentage of the cells in his or her body, including the reproductive cells that give rise to his or her sperm or eggs. In these cases, there is a possibility that the parents will have more than one child with OI. The mosaic parent may be toatlly inaffected or have only mild symptoms.

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.

OI Congenita (OI Tarda)
Part of a classificiation system for people with OI that was in general use until the early 1980's. OI congenita identified people who had a severe or fatal form of OI and who were born with fractures or experienced fractures as a newborn. This system was replaced by the current list of Types as described in the fact sheet "Fast Facts on OI," and "Novel Forms of Osteogenesis Imperfecta."

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. This system was replaced by the current list of Types as described in the fact sheet "Fast Facts on OI," and "Novel Forms of Osteogenesis Imperfecta."

OI Type I (Type I OI)
The most common and the mildest form of osteogenesis imperfecta (OI). For details regarding characteristics and health care see the fact sheets "Fast Facts on OI." (For more information about OI TypeI see the fact sheet "Living with Type I 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, 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. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

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. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

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. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

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. (For more information see the fact sheet "Novel Forms of Osteogenesis Imperfecta."

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

Ossification
Changing other tissues, including cartilage, into bone. It is the process of normal bone formation performed by the osteoblast, a cell in the body that specifically performs this function.

Osteoblasts
Bone forming cells. Part of the bone turnover cycle.

Osteoclasts
Bone removing cells 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 characterized 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. For a detailed list of characteristics of OI by type see the fact sheet "Fast Facts on OI." Two additional forms of OI have recently been identified that do not appear to have a type 1 collagen defect. For information regarding these types of OI see the fact sheet "Novel Forms of OI."

Osteomalcia (Adult Rickets)
A disease characterized by soft, bendable bones and varying degrees of pain. It is can be caused by a lack of vitamin D or a kidney disorder. It can begin during pregnancy.

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, osteoporosis and osteomalcia.

Osteoporosis
A condition in which the bones become less dense and more likely to fracture. This disease is characterized by porous bone, low bone mass and structural deterioration of bone tissue, leading to bone fragility.

Osteosclerotic
Too much bone formation.

Osteotomy
Surgically cutting a bone. It is a step in rodding surgery and may be necessary to reduce bowing (curving) of a bone.

Pamidronate
A drug in the bishosphonate family. It is prescribed under the name Aredia. It is given intravenously. It is approved by the US FDA to treat Paget's disease of bone and several other conditions. It currently is in clinical trials as a treatment for OI in infants, children and adults with severe OI. (For more information see the "Bisphosphonate Q & A" on the fact sheet page.)

Perspiration (Sweat, Diaphoresis)
Sweator diaphoresis. Some people who have OI appear to perspire more heavily than others experiencing the same room temperature.

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 the United States today have OI?" is asking about the prevalence of OI.

Rickets
A disease seen in infants and children. It is characterized by soft, bendable bones, skeletal deformities, poor growth, and frequent fractures. It is caused by a lack of vitamin D.

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. (For more information see the f
act sheet "Rodding Surgery".)

Rodding Surgery
Rodding surgery involves internal "splinting" of the long bones by means of the insertion of a metal rod. (See Rodding.)

Sclera
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.

Spontaneous Mutation
This is a change in a gene that occurs without an obvious cause, in a family where there is no history of the particular gene mutation. OI is inherited as an autosomal dominant trait. Approximately 35% of cases have no family history and are called "sporadic" cases. In sporadic cases, OI is believed to result from a spontaneous new mutation.

Stem Cell
As related to bone, this is a cell that has the capacity to proliferate and subsequently become bone cells, but in other circumstances they can become cartilage, tendons, muscle or fat. They appear to be widely distributed within the bone marrow, fat tissue and muscle. These are the cells that have the potential for cell or gene therapy for OI.

Stress Shielding
Occurs when an intramedulary rod, plate, cast or other device protects the bone from stress. This leads to less bone formation, and cortical thinning since the forces on a bone are what stimulate it to grow or remodel.

Sweat (Perspiration, Diaphoresis)
Perspiration or diaphoresis. Some people who have OI appear to perspire more heavily than others experiencing the same room temperature.

T-Score
One 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.

Trabecular Bone (Cancellous 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.

Transcription Factor
A protein that activates gene expression.

Transient Osteoporosis
A rapidly developing, painful local osteoporosis of unknown cause. The hip joint and ankle are often affected. Unlike osteoporosis, transient osteoporosis is reversible. The condition generally runs its course over 6-12 months.

Type 1 Collagen
The major structural protein which functions as a significant part of the underlying structure of bone, ligaments, skin and other connective tissue.

Type I OI(OI Type I)
The most common and the mildest form of osteogenesis imperfecta (OI). For details regarding characteristics and health care see the fact sheets "Fast Facts on OI." (For more information about TypeI OI see the fact sheet "Living with Type I OI".)

Type II OI(OI Type II)
The most severe form of osteogenesis imperfecta. Infants are usually born with multiple fractures, an unusually soft skull, 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. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

Type III OI (OI Type III)
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. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

Type IV OI (OI Type IV)
Sometimes referred to as the "moderate" form of osteogenesis imperfecta. It is in between Type I and Type III in severity. (For more information see the fact sheet "Fast Facts on OI," and the brochure "Osteogenesis Imperfecta: A Guide for Medical Professionals, Individuals and Families affected by OI.")

Type V OI (OI Type V)
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. (For more information see the fact sheet "Novel Forms of Osteogenesis Imperfecta.")

Ultrastructure
Fine structures seen with the electron microscope.

Wormian Bones
Small, irregular bones in the cranial structure that are apparent on an X-ray. Resembles the appearance of a cracked, dried-up lake bed. Wormian bones are not considered a "symptom" of OI (they cause no difficulty) but are a common finding in people with OI. Wormian bones also occur in other disorders.

Zoledronate
A bisphosphonate prescribed under the commercial name Zometa, sometimes referred to as zoledronic acid.

Zometa
The commercial name for the bisphosphonate zoledronate or zoledronic acid. It is given intravenously, but requires a shorter infusion time than Aredia (pamidronate).

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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