Hypochondroplasia - Signs and Symptoms, Diagnosis and Treatment

What Is Hypochondroplasia?

Hypochondroplasia is a genetic disorder with a characteristic small stature and disproportionately short arms, hands, legs, and feet (short-limbed dwarfism). These features are often not identified until early to mid-childhood or, in some instances, as late as adulthood. For example, in those people with hypochondroplasia, bowing of the legs usually develops during early childhood but often shows improvement spontaneously with age. Some individuals with this disorder may also have a relatively prominent forehead, an abnormally large head (macrocephaly), or other physical abnormalities associated with the condition. In addition, mild mental retardation may also be seen in approx 10 percent of the cases.

In a few cases, hypochondroplasia seems to appear randomly due to unknown reasons (sporadically) with no apparent family history, or it can be due to the disorder being familial with autosomal dominant inheritance.

What Are the Signs and Symptoms of Hypochondroplasia?

Hypochondroplasia has the primary characteristic of -

• Small stature with disproportionately short arms and legs.

• Mild to moderately short fingers and toes (brachydactyly).

• Short, broad hands and feet (short-limbed dwarfism).

• In addition, the slow growth of the child is often not apparent at birth; as mentioned above, it may not be identified until about two to three years of age, during late childhood, or as late as adulthood.

• Shortening of the limbs may be relatively mild or moderate for those with hypochondroplasia.

• During early childhood, the bowing of the legs in an outward direction (known as bowlegs or genu varum) is typically pronounced during weight bearing. However, this condition often seems to improve spontaneously during late childhood.

• The extension and rotation of the elbows also get limited in most of the affected individuals.

• Exercise beginning during early childhood may result in discomfort or minor aching of the elbows, knees, and ankles.

• These joint pain in affected adults may extend to involve the lower back. In addition, about one-third of affected individuals may also have inward curvature of the spine that is abnormally pronounced in the lower back (lordosis).

A few other symptoms of hypochondroplasia that may be seen are-

• Abnormally large head (macrocephaly).

• Relatively broader and shorter skull (brachycephaly).

• Rectangular-shaped skull with a slightly prominent forehead. However, the facial appearance is generally normal.

• Mild mental retardation may also be seen in about 10 percent of affected individuals.

What Are the Complications of Hypochondroplasia?

Medical complications of hypochondroplasia that can be seen in affected individuals include:

• Obesity.

• Sleep apnea (potentially serious sleep-related breathing disorder).

• Learning disabilities.

• Seizures.

• In young children, the opening found at the bottom of the skull gets narrowed (called foramen magnum stenosis).

• In adults, the lower spinal canal is narrowed (called lumbar spinal stenosis).

What Causes Hypochondroplasia?

Hypochondroplasia usually occurs due to a mutation (change) in a gene. It leads to slower growth of the bones and causes them to end up shorter in length than they typically would be.

Sometimes, even though the affected individual has the signs and symptoms of hypochondroplasia, no gene mutation can be found. However, this does not necessarily indicate that the possibility of hypochondroplasia has been ruled out. The mutation in their gene just might not be seen by the technology today. Or, they may have a different gene being altered that may be causing signs and symptoms of hypochondroplasia.

A child can inherit the gene causing hypochondroplasia from either parent if they have it. But most children born with the disorder have a new (or spontaneous) genetic mutation before birth, and neither of the parents has the condition.

The possibility of hypochondroplasia running in families can be understandable with genetic counselors' help.

How Is Hypochondroplasia Diagnosed?

Before birth, healthcare providers might diagnose hypochondroplasia with genetic testing through amniocentesis, prenatal ultrasound, or chorionic villus sampling (CVS). These tests are the prenatal diagnosis for genetic abnormalities and fetal infections

Most of the time, doctors can diagnose it at birth or during early childhood. For example, if a child seems shorter than other kids of the same age or the length of their arms and legs are short, doctors do a physical exam and a few tests to find the cause. These tests usually involve X-rays and sometimes genetic testing. The differences in the growth sometimes are so slight that hypochondroplasia does not get diagnosed until later in life.

How Is Hypochondroplasia Treated?

There is no permanent cure for hypochondroplasia, but research has been conducted to produce drugs that can help with bone growth. Studies on gene therapy are also being done.

A team of specialists is required for the care of people with hypochondroplasia. The group usually includes:

• A neurologist/neurosurgeon for brain and spinal cord problems.

• An orthopedic surgeon for bone abnormalities.

• Developmental pediatrician to help screen and treat any learning disability.

• A pediatrician for general routine care.

• A genetics counselor to explain the genetic changes to the families and recommend future care.

• A pulmonologist for sleep apnea.

• An occupational therapist to help with eating, writing, and other everyday activities.

Treatments for hypochondroplasia may include:

• Surgical straightening for the outward bowing of the legs.

• Surgery for spinal curvature, compression, or spinal stenosis.

• Weight management after two years of age.

• Sleep apnea treatment.

Various orthopedic procedures, including a few techniques and surgery, may be recommended to help with the treatment or correction of specific skeletal abnormalities that are usually associated with the disorder.

A cesarean or c-section is often necessary for delivery in pregnant women with hypochondroplasia.

Special services that may prove to be beneficial for the affected individuals may include physical therapy, occupational therapy, special education, and other medical, social, or vocational services. In addition, the affected individuals and their families might also benefit from genetic counseling. Other treatments for this condition involve symptomatic and supportive care.

Conclusion

Hypochondroplasia is a skeletal disorder. Early intervention may be essential to help ensure that affected children reach their potential. Then, the child can live a whole and happy life. Regular medical care will enable them to stay healthy and let doctors immediately treat and manage any health problems. Talk to a hospital social worker or anyone in the supportive care team about resources that can help the child or anyone in the family.