Hypochondroplasia is a type of skeletal dysplasia, or genetic condition that affects the way bones grow. Hypochondroplasia causes bone growth to slow down, especially in the long bones of the arms and legs, which results in disproportionate short stature and shortened limbs.1
Definitions of key terms can be found in the glossary
Hypochondroplasia is caused by a change (variant) in a gene called fibroblast growth factor receptor 3 (FGFR3), which plays a role in bone growth. In people with hypochondroplasia, FGFR3 is too active, which makes it difficult for certain bones to grow.1
Hypochondroplasia is rare, occurring in about 1 in 15,000 to 40,000 children. The variants that cause hypochondroplasia can occur either by chance or from being passed down by a parent with hypochondroplasia. In families where one parent has hypochondroplasia, there is a 50% chance that the variant will be passed down to the child.1
Chondrocytes are a type of cell responsible for bone and cartilage formation. They are essential for the development of the skeletal system.2
Chondrocytes contain a type of protein called FGFR3, which helps to slow bone growth.2
In people with hypochondroplasia, FGFR3 becomes overactive. This reduces bone growth and leads to the short stature and other distinct features of hypochondroplasia.
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Children with hypochondroplasia have disproportionate short stature (shorter than average for their age).1 Other distinct physical features may include short arms and legs, a head that is larger than average for age, bowed legs, and curved spine.1,4
Each child’s experience with hypochondroplasia is unique.
Medical complications for hypochondroplasia may occur in childhood and throughout life, and may include:1,4,5
Not all children with hypochondroplasia will experience these specific issues, and some may encounter other challenges not mentioned here.
Individuals with hypochondroplasia should have regular check-ups by an experienced healthcare team. Talk to your doctor if you have any questions about what your child is experiencing.
Sometimes hypochondroplasia can be detected and diagnosed before birth through prenatal ultrasound and/or genetic testing.6 More commonly, children with hypochondroplasia are diagnosed at birth or early in childhood, usually by physical exam and X-rays.1 Genetic testing can confirm the diagnosis.1 Because hypochondroplasia is rare and signs and symptoms may be varied and/or subtle, diagnosis may be delayed.1
Only a doctor can diagnose hypochondroplasia
