Achondroplasia is the most common cause of disproportionate short stature (dwarfism). It is a type of skeletal dysplasia. Intelligence is unaffected by achondroplasia, and life expectancy is usually near normal, although complications can reduce survival.
Genetics
Achondroplasia is caused by pathogenic variants in the FGFR3 gene on chromosome 4. Achondroplasia results from either a sporadic mutation or inheritance of an abnormal copy of this gene. The condition is inherited in an autosomal dominant pattern.
Homozygous achondroplasia (two abnormal gene copies) is usually lethal before birth or in the neonatal period. Therefore, almost all affected patients are heterozygous (one normal copy and one abnormal copy).
FGFR3 mutations usually cause overactivity of the FGFR3 receptor. This inhibits normal cartilage development at the growth plates, reducing longitudinal bone growth and leading to short bones and short stature.
Features
Patients with achondroplasia have disproportionate short stature. The average height is just over 4 feet. The limbs are most affected by the reduced bone length. The femur and humerus (proximal limbs) are affected more than the bones of the forearm and lower leg. The spine length is less affected, and patients have a relatively preserved trunk length.
Other features of achondroplasia include:
- Short digits
- Bow legs (genu varum)
- Disproportionate skull
- Foramen magnum stenosis, with potential cervical cord compression and hydrocephalus
Different areas of the skull grow by different methods, some of which are affected by achondroplasia more than others. This leads to a disproportionate skull. The skull base grows and fuses via endochondral ossification, which is affected by achondroplasia and leads to a flattened mid-face and nasal bridge, and foramen magnum stenosis. The cranial vault (dome-shaped part of the skull containing the brain) grows and fuses via membranous ossification, which is unaffected by achondroplasia, leading to relative macrocephaly and frontal bossing (prominent forehead).
Complications
- Recurrent otitis media and middle-ear effusions, due to cranial abnormalities
- Delayed motor milestones
- Kyphoscoliosis
- Lumbar lordosis
- Dental crowding
- Spinal stenosis
- Obstructive sleep apnoea
- Obesity
- Foramen magnum stenosis, with potential cervical cord compression and hydrocephalus
Management
There is no cure for the underlying genetic condition. Management will involve the multidisciplinary team to support the patient with development and maximise functioning and monitor for complications:
- Paediatricians
- Specialist nurses
- Physiotherapists
- Occupational therapists
- Psychologists
- Social workers
- Dietitians
- Orthopaedic surgeons
- ENT surgeons
- Geneticists
Vosoritide is a medication that counters the FGFR3 overactivity and has been shown to improve growth velocity in children with achondroplasia. It does not currently have marketing authorisation and is not in use in the UK.
Leg lengthening surgery can add height, but requires extensive surgery and recovery. It involves cutting the bone (osteotomy) and separating the two parts, creating a gap between them (distraction). Over time, bone forms between the two parts, creating a longer bone. This is not a routine treatment. It is controversial and has the potential to lead to significant problems, including chronic pain and reduced function.
Last updated July 2026
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