Achondroplasia is the most common form of dwarfism. Most children with achondroplasia and don't require treatment for the condition. However, children with certain issues such as spinal stenosis or spinal cord compression may need medical care. Here at Cook Children's, our orthopedic team works with other specialty teams to provide the best kid-focused care possible for your child.
Achondroplasia is a genetic disorder that interferes with bone growth and causes dwarfism (short stature). In fact, it is the most common type of dwarfism. So what it dwarfism? Dwarfism:
- Is characterized by short stature. This means an adult height of 4 feet 10 inches or under, according to the advocacy group Little People of America (LPA). For children, this means being below the height growth curve for their age, which would be less than the 2nd percentile.
- Can and most often does happen in families where both parents are of average height
- Can be caused by any one of more than 400 conditions. Most of these are genetic and classified as skeletal dysplasias (conditions of unusual cartilage and bone growth).
Dwarfism is not:
- An intellectual disability. Most people with dwarfism have normal intelligence.
- A disease that requires a "cure." most little people live long, fulfilling lives.
- A reason to assume someone is incapable. Little people go to school, work, drive cars, marry, and raise children, just like their average-size peers.
During a baby's development in the womb, much of the skeleton is made up of a tough, flexible tissue called cartilage. Normally, cartilage is converted to bone by a process called ossification. With achondroplasia, the body has a problem growing cartilage and converting it to bone, especially in the long bones of the arms and legs. This results in shorter bones, short stature, and often a large head with a prominent forehead. It can also cause knock-knees, bow-leggedness, or excessive curving of the lower back (lordosis or kyphosis).
Achondroplasia is one of a group of disorders called chondrodystrophies, or osteochondrodysplasias.
Achondroplasia may be inherited as an autosomal dominant trait, which means that if a child gets the defective gene from one parent, the child will have the disorder. If one parent has achondroplasia, the infant has a 50% chance of inheriting the disorder. If both parents have the condition, the infant's chances of being affected increase to 75%.
However, most cases appear as spontaneous mutations. This means that two parents without achondroplasia may give birth to a baby with the condition.
The typical appearance of achondroplastic dwarfism can be seen at birth. Symptoms may include:
- Abnormal hand appearance with persistent space between the long and ring fingers
- Bowed legs
- Decreased muscle tone
- Disproportionately large head-to-body size difference
- Prominent forehead (frontal bossing)
- Shortened arms and legs (especially the upper arm and thigh)
- Short stature (significantly below the average height for a person of the same age and sex)
- Narrowing of the spinal column (spinal stenosis)
- Spine curvatures called kyphosis and lordosis
During pregnancy, a prenatal ultrasound may show excessive amniotic fluid surrounding your unborn infant.
Examination of your baby after birth shows increased front-to-back head size. There may also be signs of hydrocephalus ("water on the brain"). X-rays of the long bones can reveal achondroplasia in your newborn.
There is no specific treatment for achondroplasia. Related abnormalities, including spinal stenosis and spinal cord compression, should be treated when they cause problems.
Occasionally, children with achondroplasia will develop health problems or complications. These include:
- Breathing problems from a small upper airway and from pressure on the area of the brain that controls breathing
- Lung problems from a small ribcage
People with achondroplasia seldom reach 5 feet (1.5 meters) in height. Intelligence is in the normal range. Infants who receive the abnormal gene from both parents do not often live beyond a few months.