Q: What are the clinical features of achondroplasia?

A. The patients have a disproportionate short stature with a normal trunk, short arms and short legs. There is proximal shortening of the limbs (rhizomelic dwarfism). The average adult height is 4 feet. The head appears larger than the body, with a prominent forehead and flattened bridge of the nose. Teeth may be crowded with poor alignment. Spine is usually straight in the upper back with a marked lumbar lordosis. Abnormalities of the thoracolumbar vertebra may lead to kyphosis in infancy, which disappears once the child starts walking, but may cause spinal cord compression is adolescents. There may be bowing of the legs and feet are generally short and flat. Hands are short with stubby fingers and there may be a trident hand (separation between the middle and ring fingers).

Children with achondroplasia usually are slow to sit, stand & walk (delayed motor milestones). However, they are able to lead independent and productive lives.

Q: What are the complications of achondroplasia?

In infancy or early childhood, these children may die suddenly in sleep due to compression of the upper spinal cord. Narrowing of the foramen magnum and abnormalities of the upper cervical vertebra cause the compression.

These children may have frequent otitis media, leading to conductive deafness. These children may also develop symptomatic hydrocephalus. The most common complication in adults is lumbar spinal cord compression due to lumbar spinal stenosis. This complication is treatable with surgical decompression, if diagnosed early.

These children may also have airway obstruction due to large tonsils and small facial structure.

Q: How does Achondroplasia occur?

Achondroplasia is an autosomal dominant condition with the abnormal gene located on chromosome 4. However, 75% of cases are new mutations. The parents of children with achondroplasia resulting from a new mutation are usually of normal stature. Their chance of having a second affected child is extremely small. It has been observed that father above 40 years of age are more likely to have children with achondroplasia and other autosomal dominant conditions.