Axial spondylometaphyseal dysplasia

Axial spondylometaphyseal dysplasia is a genetic disorder of bone growth. The term “axial” means towards the center of the body. “Sphondylos” is a Greek term meaning vertebra. “Metaphyseal dysplasia” refers to abnormalities at the ends of long bones. Axial spondylometaphyseal dysplasia primarily affects the bones of the chest, pelvis, spine, upper arms and upper legs, and results in shortened stature. For reasons not well understood, this rare skeletal dysplasia is also associated with early and progressive vision loss. The underlying genetic cause of axial spondylometaphyseal dysplasia is currently unknown. It is thought to be inherited in an autosomal recessive fashion.^[1]

Common signs and sympotms of axial spondylometaphyseal dysplasia, include short stature, chest, spine, limb, and pelvic bone changes, and vision disturbance.^[1]

People with axial spondylometaphyseal dysplasia may have a normal birth length, but demonstrate growth failure by late infancy to early childhood. A measurement called standard deviation (SD) is used to compare the height of different children. If a child's height is more than 2 SD's below the average height of other children the same age, the child is said to have short stature. This means that almost all of the other children that age (more than 95% or 19 out of 20) are taller.^[2] Individual case reports of children and an adult with axial spondlometaphyseal dysplasia demonstrate height as being between 2 to 6 SD’s below average.^[1]

Infants with axial spondlometaphyseal dysplasia tend to have a shortened chest with short ribs, a condition called thoracic hypoplasia. Thoracic hypoplasia tends to become more prominent in childhood, and less noticeable in adolescence and adulthood. Thoracic hypoplasia may cause mild to moderate breathing problems in infants and recurring lung infections in childhood.^[1]

Young children with axial spondlometaphyseal dysplasia have shortened upper arms and upper leg bones, which may become less prominent as they grow.^[1]

Spine changes include vertebrae that have a flattened appearance on x-ray. This finding is typically mild in infancy and early childhood, becomes more apparent in late childhood, then self-corrects by adulthood. Some individuals with axial spondylometaphyseal dysplasia develop scoliosis (curvature of the spine).^[1]

Pelvic bone changes can be seen in infants and children. Some of these changes self-correct by adulthood.^[1] A condition called “coxa vara” (where the angle between the top of the femur and the femoral shaft is smaller than normal) is common beginning in late childhood and persists through adulthood.^[1] Coxa vara may affect gait (pattern or way of walking). Some people with axial spondlometaphyseal dysplasia have minor bone changes in their knees.^[1]

Vision problems, including retinitis pigmentosa and/or optic atrophy, become evident in infancy or early childhood and rapidly worsen.^[1] Retinitis pigmentosa causes cells in the retina to breakdown and die, eventually resulting in vision loss. Optic atrophy causes vision to dim and reduces the field of vision. It also reduces the ability to see fine detail and color (ie., colors will seem faded). With the progression of optic atrophy, a person's pupil reaction to light diminishes and may eventually be lost. Long term outlook for vision for people with axial spondylometaphyseal dysplasia is poor.^[1]

Axial spondylometaphyseal dysplasia is thought to be a genetic disorder, however the underlying genetic cause is not known.^[1]

An autosomal recessive pattern of inheritance is suspected in axial spondylometaphyseal dysplasia. You can learn more about autosomal recessive inheritance at the following links:

MedlinePlus.gov: http://www.nlm.nih.gov/medlineplus/ency/article/002052.htm
Genetic Home Reference:  http://ghr.nlm.nih.gov/handbook/illustrations/autorecessive

To learn more about your family's specific risks, we recommend that you speak with a genetics professional. Genetics clinics are a source of information for individuals and families regarding genetic conditions, treatment, inheritance, and genetic risks to other family members. More information about genetic consultations is available from Genetics Home Reference at http://ghr.nlm.nih.gov/handbook/consult. To find a genetics clinic, we recommend that you contact your primary healthcare provider for a referral.

The following online resources can help you find a genetics professional in your community:

• GeneTests has a searchable directory of US and international genetics and prenatal diagnosis clinics.
• The National Society of Genetic Counselors provides a searchable directory of US and international genetic counseling services.
• The American College of Medical Genetics has a searchable database of US genetics clinics.
• The University of Kansas Medical Center provides a list of US and international genetic centers, clinics, and departments.
• The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.

There is no specific treatment for axial spondylometaphyseal dysplasia. Symptoms such as lung infections, breathing difficulties, coxa vara, scoliosis, retinitis pigmentosa, and optic atrophy are managed individually. Specialists such as opthmologists, geneticists, and orthopedists work in concert in devloping an individualized treatment plan. We are unaware of any cases describing the use of growth hormone therapies for treatment of short stature caused by axial spondylometaphyseal dysplasia. Treatment of skeletal dysplasias with growth hormone therapy must be done with caution. 

The Little People of America, Inc Web site lists articles on repiratory and breathing problems in people with skeletal dysplasias, including an article titled Breathing Problems Among Little People: When to Be Concerned.

Detailed information related to the management of retinitis pigmentosa can be accessed through GeneReviews and the Treatment and Medication sections of Medscape Reference.

Detailed information related to the management of coxa vara can also be found in the Treatment sections of a Medscape Reference review article on this condition.

Johns Hopkins Department of Orthopedic Surgery offers a Patient Guide to Scoliosis.

MedlinePlus.gov provides information on optic atrophy. 

Further medical support resources can be found through the Little People of America, Inc.