What is a skeletal dysplasia?
Skeletal dysplasia is a term used to describe over 450 genetic conditions that affect bone and cartilage development, resulting in abnormal bone length, density and/or shape. About one in 5,000 children are born with a skeletal dysplasia. Symptoms of a skeletal dysplasia depend on the gene involved and the area(s) of the body that are affected. Symptoms can vary between people with the same skeletal dysplasia, even within a family (e.g., parent and child). A skeletal dysplasia cannot be cured. Treatments are usually supportive and aim to improve quality of life.
Common skeletal dysplasias
Common types of skeletal dysplasia include, but are not limited to:
- achondroplasia (dwarfism), caused by variants in the FGFR3 gene
- type II collagen disorders, a group of conditions that are caused by variants in the COL2A1 gene
- osteogenesis imperfecta (brittle bone disease), caused by variants in over 20 genes, with the most common being the COL1A1 and COL1A2 genes
Signs and symptoms of skeletal dysplasia
Skeletal dysplasia often affects the limbs, spine, torso/chest and skull. This can cause a range of symptoms, including:
- shorter height
- differences in the shape of bones on X-ray, which may present as bowed legs, short arms or legs
- fragile bones or stiff joints
- feet that curve inwards (club foot)
- chest and rib abnormalities, which can affect a person’s ability to breathe
- changes to the spine, including spinal curves (i.e., kyphosis, lordosis, scoliosis)
- differences in facial features (e.g., prominent forehead or large head)
Children with skeletal dysplasias may have delays achieving their motor milestones (e.g., holding their head up, sitting up, walking).
Causes of skeletal dysplasias
Skeletal dysplasias are caused by a variant or variants in a person’s genetic information (gene). We usually inherit one copy of a gene from each parent. Genes give our body instructions for proper growth and development. Skeletal dysplasias are typically caused by change(s) in genes that are important for bone development.
Bones are rigid structures that form the skeleton of our bodies. Bones provide support, shape and movement, and they protect various organs of the body. Variants in genes that affect bone development may also play a role in other parts of the body (e.g., brain, heart, vision, hearing). The symptoms of a skeletal dysplasia are highly dependent on the gene involved.
The gene variant(s) can be new in the child for the first time (de novo) or inherited (one or both parents carry the genetic variant that is passed down to the child).
How is skeletal dysplasia diagnosed?
Some skeletal dysplasias can be diagnosed before birth. If there is a family history of a skeletal dysplasia and the gene variant is known, targeted prenatal genetic testing may be done if the family wishes to know if the pregnancy is affected or not. If an ultrasound suggests the possibility of a skeletal dysplasia by measurements (e.g., shortened bones) with no known family history, prenatal genetic testing may be offered. However, a diagnosis may or may not be identified as ultrasound findings are typically identified late in pregnancy and not specific enough to identify the type of skeletal dysplasia.
Genetic testing during pregnancy can be done in one of the following ways:
- by amniocentesis (test of the amniotic fluid that surrounds the baby) after the 15th week of pregnancy
- by chorionic villus sampling (testing the placental tissue) as early as the 11th to 13th week of pregnancy
Most skeletal dysplasias are diagnosed after birth. Signs and symptoms of a skeletal dysplasia may not appear until a child gets older. Medical imaging (e.g., X-ray, CT (computerized tomography) scan, MRI (magnetic resonance imaging)) and physical examinations are useful to determine the type of skeletal dysplasia. Genetic testing may be used to confirm a clinical diagnosis. Some skeletal dysplasias may not be diagnosed even with genetic testing as the underlying genetic cause of all skeletal dysplasias has not been found.
How is a skeletal dysplasia treated?
Treatments for a skeletal dysplasia vary depending on the diagnosis and complication. If your child’s condition is mild or does not require treatment right away, your health-care provider will monitor your child’s health over time through routine checkups. Treatments may include interventions, such as physical therapy or medication, to reduce pain and other unpleasant physical symptoms. If your child’s symptoms are severe and cause significant impairments, surgery may be recommended.
Who is involved in treating skeletal dysplasias?
Since skeletal dysplasias often impact more than one area of the body, your child may have multiple specialists who participate in their care. These may include:
- orthopaedic surgeons
- geneticists and genetic counsellors
- family physician or paediatrician
- neurosurgeons
- neurologists
- respirologists
- physiotherapists
- occupational therapists
- dietitians
- social workers
Complications of a skeletal dysplasia
Depending on the area(s) of the body affected, children with skeletal dysplasia may experience:
- fragile bones and dental complications (e.g., missing teeth, misaligned teeth)
- vision or hearing abnormalities
- pain, discomfort and difficulties with movement or limited movement
- breathing difficulties
- neurological abnormalities (e.g., seizures)
Living with a skeletal dysplasia
Children with a skeletal dysplasia may need accommodations at school and home. Children with short stature can face challenges to gain and maintain their independence. This may include using a step stool or sitting at the front of the classroom with an appropriately sized desk and chair. Short stature may make it difficult for a child to keep up with peers and may pose a safety issue in the playground or in transitioning in and out of the classroom. A child with short stature may need help with activities in which height could pose a challenge.
While it is important to ensure that your child is receiving the necessary supports and accommodations, it is also important to allow them to participate in activities safely and independently at school and home. For example, children with skeletal dysplasia may not be able to participate in high-contact sports (e.g., hockey), but swimming can be a safe sport. Discussions between parents and family, your child’s medical team and your child can help to clarify what accommodations are best suited for your child.
It is important to note that children with visible differences can sometimes be bullied by their peers. This topic should be an open discussion with the child, family, school staff and medical professionals.
At SickKids
At SickKids, children are typically referred for initial assessment to the skeletal dysplasia clinic located in the Department of Clinical Genetics.
Children with a skeletal dysplasia may also be monitored in the skeletal dysplasia clinic located in the department of orthopaedics. This clinic is staffed by an orthopaedic surgeon, geneticist and genetic counsellor.
References
Krakow D. (2015). Skeletal dysplasias. Clinics in perinatology, 42(2), 301–viii. https://doi.org/10.1016/j.clp.2015.03.003
Marzin, P., & Cormier-Daire, V. (2020). New perspectives on the treatment of skeletal dysplasia. Therapeutic advances in endocrinology and metabolism, 11, 2042018820904016. https://doi.org/10.1177/2042018820904016