Achondroplasia

Achondroplasia is caused by a mutation (change) in a gene on chromosome 4 called FGFR3 that controls the production of a receptor (receiver) for fibroblast growth factor 3.  The receptor found in the growth plate does not work as it should, which means that growth is inhibited. In most cases, it is a new mutation, meaning that the parents do not have the gene. However, a child with achondroplasia inherits the gene in an autosomal dominant manner. This means that the mutated gene is dominant over a non-mutated gene, and if a person with achondroplasia has children, the gene can be passed on to them even though the other parent does not carry the mutation. 

The world today is not adapted for people under 152 cm, meaning that many situations in everyday life can become challenging if you are shorter than that. Door handles, locks, switches, sinks, shelves, gas pedals, etc., are often out of reach for short people. Short arms that cannot be fully extended can also make personal hygiene difficult. 
 
Since the condition often narrows the canal for the spinal cord, so-called spinal stenosis, it might result in neurological symptoms such as increased reflexes, weakness in the legs and/or the throat and respiratory muscles, poorer coordination, and increased sweating. Above all, adults with achondroplasia often have problems with spinal stenosis. Along with neurological challenges, it can also cause problems such as leg pain, tingling in the legs, paralysis, and urinary incontinence. 
 
A tight throat can cause sleep apnea (nocturnal breathing pauses) and snoring. Motor development is often delayed, and the onset of walking is usually around 18 months. However, cognitive (intellectual) development and ability are completely normal. During infancy, many children develop a crooked back (kyphosis) due to muscle weakness, which usually disappears at the start of walking and turns into an often pronounced curvature (lordosis) in the lumbar spine. Together with other skeletal abnormalities in the pelvis and legs, this results in a somewhat wobbly gait. 
 
Apart from the elbows, which are often stiff, the ligaments around the joints are loose, combined with the fact that the calf bone (fibula) is often longer than normal in relation to the shin bone (tibia). This often results in the development of bow-leggedness, with instability in the knee joints and misalignment around the knee and ankle, leading to the knee and ankle being loaded obliquely, which can lead to pain and osteoarthritis in the long run. 

In many cases, no treatment is needed. Treating misalignments or short stature is an individual decision, and we assess and suggest treatment based on each patient's own desires. The goal of treatment is always to improve the patient's function or prevent future problems. 

Children are referred to the Dysplasia team at Karolinska University Hospital, following the patient until they are fully grown. After age 18, the patient is assigned to the Deformity team at the adult orthopedist if problems with the musculoskeletal system still occur.  
 
When the child is newly born and achondroplasia has been diagnosed, an MRI examination is carried out to see how narrow it is for the brainstem in the foramen magnum. The narrowness can cause breathing problems and weakness in the arms and legs. In excessively narrow conditions, the neurosurgeon may decide on surgery to widen the space in the foramen magnum. 
 
As people with achondroplasia often have narrow airways, breathing support, such as CPAP or BIPAP, or having to remove the tonsils and/or adenoids might be needed. Bite abnormalities can be remedied with braces. 
 
During growth, bow-leggedness can be remedied or reduced by temporarily slowing the development on the outside of the knee by putting a small so-called eight-plate over the growth plate. Grown-ups with a misalignment that causes problems or can lead to osteoarthritis and, therefore, need correction require a slightly more extensive procedure, a so-called osteotomy (splitting the bone) that re-angles and possibly lengthens the leg.    
 
Since today's society is adapted to a minimum height of approximately 150 cm, people with short stature may experience some functional restraints. This can be driving a car, going to the toilet, doing housework, etc. Far from everyone chooses to undergo leg lengthening. The benefit of the procedure must carefully be considered against the risks that are always associated with the procedure. Many patients manage well by just making adjustments in their homes and cars.  
 
At Karolinska University Hospital, we have extensive experience with bone lengthening in achondroplasia. We always recommend correcting serious misalignments that can otherwise lead to osteoarthritis. Still, if a patient is short and feels this is a problem in everyday life, we can also offer an extension of arms or legs to achieve increased function and quality of life.