Alternative Names
osteochondrodysplasia; dwarfism
Symptoms & Characteristics
Skeletal dysplasias are a group of more than 200 disorders characterized by abnormalities in the growth and/or remodeling of cartilage and bone. Skeletal dysplasias typically cause disproportionate short stature (disproportionate dwarfism), meaning some parts of the body are small while others are of average size or above-average size. Short stature refers to any person who is significantly below the average height for a person of the same age, sex, and ethnicity - typically defined as less than 3rd percentile on appropriate growth charts. Skeletal dysplasias can also affect the skull, spine, and limbs (arms and legs) in varying degrees.
Skeletal dysplasias are commonly grouped into two categories: short-limb dysplasias and short-trunk dysplasias. People with short-trunk dysplasias have a shortened trunk with longer limbs, while people with short-limb dysplasias have an normal sized trunk but shortened limbs.
Examples of more common short-limb dysplasias include:
Achondroplasia is characterized by dwarfism with an average-size trunk and shortened upper parts of their arms and legs. Other common features can include a large head with a prominent forehead, a flattened nasal bridge, shortened hands and fingers, and reduced muscle tone.
Diastrophic dysplasia is characterized by dwarfism with very short arms and legs. Most affected people also have early-onset joint pain (osteoarthritis) and joint deformities called contractures, which restrict movement. Other features can include cleft palate, clubfoot and ears with a characteristic cauliflower appearance.
Achondrogenesis is a group of severe, lethal disorders characterized by dwarfism with a small body, short limbs, and other skeletal abnormalities.
Thanatophoric dysplasia is characterized by dwarfism with extremely short limbs and folds of extra (redundant) skin on the arms and legs. Other features can include a narrow chest, short ribs, underdeveloped lungs, and an enlarged head with a large forehead and prominent, wide-spaced eyes.
Some examples of short-trunk dysplasias include:
Spondyloepiphyseal dysplasias (SED) refers to a group of short-trunk dysplasias. In some forms, a lack of growth in the trunk area may not become apparent until childhood; other forms are apparent at birth. Other features can include clubfeet, cleft palate, and a barrel-chested appearance.
Kniest dysplasia is characterized by dwarfism with other skeletal abnormalities and problems with vision and hearing.
Spondyloepimetaphyseal dysplasia, Strudwick type is characterized by dwarfism with a very short trunk and shortened limbs. Other features can include skeletal abnormalities and problems with vision.
Treatment
The prognosis, management and treatment of skeletal dysplasias depend on the specific type and symptoms. In some cases, early diagnosis, routine surveillance and treatment can help to manage some of the symptoms and prevent related problems.
How Common Is It?
About 1 in 4,000 to 1 in 5,000 newborns are affected with a skeletal dysplasia. However, this incidence may be underestimated, as the characteristics of some skeletal dysplasias may not become fully apparent until childhood. Achondroplasia is the most common skeletal dysplasia and is responsible for 70% to 80% of all cases of dwarfism.
Genetics & Inheritance
The different types of skeletal dysplasias are caused by mutations in different genes.
- In some cases, multiple genes are associated with the same type.
- In other cases, different mutations in the same gene cause different types.
The mode of inheritance varies by type. Skeletal dysplasias can have autosomal recessive, autosomal dominant, X-linked recessive, or X-linked dominant inheritance.
A genetic consultation with a trained genetic professional is important for a complete evaluation, accurate diagnosis, as well as discussion of the benefits and limitations of testing and recurrence risk.
Genetic Testing
Clinical genetic testing for some skeletal dysplasias may be available through an in person genetic consultation for people who are considered at risk. Use our find a genetic professional directory to locate a trained genetic professional in your area.
Support & More Information
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