What is Dwarfism (Achondroplasia)?

Dwarfism or Achondroplasia is a condition where bone growth is stunted producing a short stature and other distinctive characteristics. It can be detected in utero, at birth, or noticed as the child grows.

Causes, Incidence and Risk Factors

Dwarfism is also one of the oldest recorded birth defects. It was first described by Egyptian obstetricians.

Dwarfism (achondroplasia) is a genetic disorder, affecting 1 in 25,000 children. The primary cause of this disease is the mutation of a gene called FGFR3 (Fibroblastic Growth Factor Receptor 3). This gene is responsible for the lengthening of bones. A defect in this gene produces short, wide bones. This genetic mutation generally occurs spontaneously in children with no family history of the illness. In mild cases, where the degree of mutation is minimal, stunted growth is the only effect. In some severe cases, improper growth of the bone compresses the spinal cord, causing neurological complications and mental retardation.

Dwarfism can affect both sexes and every race. It is a genetically acquired disease. If either parent has this condition, then there is an increased risk that their children will develop dwarfism as well. In addition, this ailment can be traced to men over the age of 40, who produce offspring.

Signs and Symptoms

Arms and legs are short, with short fingers and toes. The chest and abdomen are normal in size, but the head is disproportionately larger. The forehead is prominent and the nose is flat. The fingers are short and thick, with a separation between the ring finger and the middle finger. This is described as, a Trident hand.

There is also bowing of the legs, which causes a waddling gait. The nasal passages are affected. As a result, tonsillitis and ear infections are common. Furthermore, there can be sleep abnormalities and episodes of difficulty breathing.

In extreme cases, there may be associated brain and hormonal dysfunction, causing mental retardation and sexual abnormalities. The risk of cognitive and sexual malfunction decreases following infancy. As an infant, there may also be difficulty standing and walking. Although there is a delay in normal motor development, the intelligence of most children suffering from Dwarfism is generally not affected. Most individuals learn to adapt to their condition and go on to lead relatively normal lives.

Screening and Diagnosis

The most important complication is the narrowing of the foramen magnum (an opening in the base of skull from where the spinal cord starts). Narrowing in this region affects vital structures that control respiration and blood pressure. A MRI or CT scan may be necessary to rule out foramen magnum compression. A thorough clinical examination is done to rule out other causes of stunted growth. X-rays are needed to eliminate, impending soft tissue compression, in the hands, which can cause carpal tunnel syndrome.

Newer diagnostic tests are available, that can detect dwarfism (achondroplasia) even before a child is born.

Treatment

• Human growth hormone supplementation
• Leg lengthening surgeries
• Surgical correction for spine and bone abnormalities
• Surgical decompression to relieve soft tissue compression like foramen magnum syndrome decompression or carpal tunnel syndrome.
• Surgical intervention according to complications

Outlook

Many individuals with Dwarfism choose to participate in genetic counseling before having children. Additionally, there is an increased risk for rheumatic heart disease. Eighty percent (80%) of those with Dwarfism have a definitive rheumatic heart disease risk. It is essential that sufferers are continually monitored by a physician.

Complications:

• Foramen magnum syndrome
• Hydrocephalus
• Carpal tunnel syndrome
• Clubbed feet

References

1. Harrison's Principle of Internal Medicine, 15th Edition.
   
   
2. Disorders of bone and mineral metabolism, Chapter 345