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Glossary

Carrier:

A carrier is someone who does not have a disease, but has one copy of a faulty, disease-causing gene. Both parents must be carriers of the same faulty gene to produce a child who has the disease.

Cervical fusion:

Surgical procedure where bone is removed from the legs and inserted into the neck where it grows to form a firm support joining the top two vertebrae to the base of the skull.

Cervical myelopathy:

Compression or squeezing of the spinal cord that can eventually lead to paralysis or death.

Clinical Trial:

A clinical trial is a research study in human volunteers to answer specific health questions..

Conductive deafness:

Deafness due to a defect in the sound conducting apparatus in the external auditory canal or middle ear. This defect can result in a difference in pressure behind the ear drum, the outer ear canal, and the atmosphere. Conductive deafness may be improved by the insertion of tubes into the ear.

Corneal clouding:

The clear layers of the cornea in the eye become cloudy due to the build up of GAG in the eye. It may make it difficult to see in dim or very bright light.

DNA (deoxyribonucleic acid):

Genetic material in cells that holds the inherited instructions for growth, development, and cellular functioning.

Echocardiogram:

A non-invasive diagnostic method that uses sound waves to create a moving picture of the ventricular function of the heart.

Enzyme replacement therapy (ERT):

Medical treatment to replace an enzyme in patients in whom that particular enzyme is absent or deficient. It is usually given as an intravenous infusion. There are currently approved ERTs for six lysosomal storage disorders, including ERTs for MPS I and MPS VI.

GALNS:

Commonly used abbreviation for N-acetylgalactosamine-6-sulfatase, the enzyme identified as missing in Morquio A patients.

Genetic disease:

A disease caused by abnormalities in genes or chromosomes.

Genu valgum:

Commonly known as “knock knees”. The knees are bowed in and touch each other when the legs are straightened.

Gibbus or kyphosis:

The hump seen in a deformed spine caused by the abnormalities of the vertebrae.

Glycosaminoglycans (GAG):

Long chains of sugar molecules used in the building of bones, cartilage, skin, tendons and many other tissues in the body. They are continually made and broken down in the lysosome in the cell. In various MPS diseases, the body lacks the specific enzymes necessary to break down GAG. The accumulated GAG in the body leads to the symptoms associated with MPS diseases.

Halo:

Metal ring attached to the outside of the skull following cervical fusion surgery. It immobilizes the neck to allow the bone inserted into the neck to fuse with the bone at the base of the skull.

Heart murmur:

Abnormal heart sounds produced by turbulent blood flow. Generally caused by damage to the heart valves from stored GAG.

Hepatosplenomegaly:

An enlargement of the liver and spleen caused by the storage of GAG.

Hernia:

Protrusion of part of the abdomen contents through a weak spot in the abdominal wall. Common hernia sites are in the umbilical and inguinal areas.

Incidence:

The frequency of new cases of a disease or condition in a population. The incidence of MPS IVA is estimated to be 1 in 200,000 to 1 in 300,000 live births.

Intubation:

Insertion of a tube into the trachea to assist with breathing. Used when patients receive anesthesia during surgery.

Keratan sulfate (KS):

A GAG that patients with MPS IVA are unable to break down due to missing enzyme. The keratan sulfate remains stored in the cells and leads to progressive damage.

Lysosomal storage disorders:

Disorders caused by deficiency of specific lysosomal enzymes that normally degrade glycoproteins, glycolipids, or mucopolysaccharides.

Lysosome:

An organelle inside cells that is part of the intracellular digestive system. GAG that is not broken down or recycled as normal builds up in lysosomes resulting in disease symptoms.

Morquio A:

Dr. Luis Morquio, the Uruguayan physician, who first described Morquio A syndrome in 1929. It was later discovered that there are two forms of the disorder (Type A and Type B), caused by different enzyme deficiencies.

MPS IVA:

Mucopolysaccharide storage disorder characterized by short stature, severe bone disease, and preservation of intelligence. Patients with this syndrome have a deficiency of the enzyme which results in the accumulation of glycosaminoglycans.

Mucopolysaccharidosis (MPS):

A group of metabolic disorders caused by the absence or malfunctioning of lysosomal enzymes needed to break down molecules called glycosaminoglycans. MPS IVA is considered an MPS disorder.

Mucopolysaccharides:

Original name given to chains of sugar molecules used in the building of bones, cartilage, skin, tendons, and many other tissues in the body. They are now commonly referred to as glycosaminoglycans.

Mutation:

A change in a gene that could potentially be transmitted to offspring.

Myringotomy:

Incision made into the ear drum to allow drainage of fluid, followed by the insertion of a tube to prevent fluid build up. Used to treat conductive deafness.

N-acetylgalactosamine 6-sulfatase:

Enzyme that is absent or deficient in MPS IVA patients. Commonly abbreviated as GALNS.

Odontoid dysplasia:

Malformation of the bones that stabilize the connection between the head and neck. This malformation often leads to the need for cervical fusion to prevent compression or injury to the spinal cord.

Platyspondyly:

Flatness of the vertebral bodies as a result of poorly formed vertebrae. This can lead to compression of the vertebrae or backward slippage of the vertebrae resulting in a gibbus.

Pulmonary function test:

Test to measure the condition of the respiratory system by measuring the expiratory flow, lung volumes and capacities.

Sensorineural deafness:

Deafness caused by damage to the tiny hair cells in the inner ear. May be improved by the use of hearing aids.

Sternum:

Breastbone that is normally joined to the spine. Due to abnormalities in the spine in MPS IVA patients, it may assume a more prominent or beak shape. The ribs become fixed and may cause restriction of efficient breathing.

Subluxation:

A partial dislocation of a joint.

Thorax:

The portion of the body that lies between the base of the neck and the diaphragm. The sternum is part of the thorax.

Trachea:

The windpipe that connects the larynx to the bronchi. In MPS IVA patients it continues to grow normally while the cervical spine may not. As a result patients may have to tilt their heads back in to prevent it kinking or blocking their airway.

Vertebra:

The bones that comprise the spinal column.