Achondroplasia: the most common cause of dwarfism

Achondroplasia is the most frequent type of a group of conditions called bone dysplasia. It is the most frequent cause of severe growth delay (dwarfism) and results from by bone and cartilage complications. Achondroplasia is usually detected during routine ultrasound examinations in the third trimester of pregnancy due to the presence of short bones in the limbs. It is then confirmed with genetic and molecular tests. It is sometimes diagnosed at birth when the physical characteristics of dwarfism show and is confirmed by radiological diagnosis.

What causes achondroplasia?

Achondroplasia is caused by a genetic mutation that affects bone formation (specifically the so-called endochondral ossification). Although it is passed through the genes, in 80% of cases the child’s parents are not affected.

Symptoms and characteristics of achondroplasia

At birth, infants with achondroplasia present a typical appearance of disproportionately short limbs and a large head with depressed nasal bridge and prominent jaw. Achondroplasic dwarfism is characterised by affecting the limb bones closest to the body (the humerus and femur). Other characteristics are thick skinfolds with the appearance of excessive muscular tissue, global hypotonia with marked laxity of the joints except the elbow which is usually limited in stretching, short hands with limited separation between the middle and ring fingers (trident deformity) and the three central fingers of the same length ( "starfish" deformity). During growth, patients present a delay in the acquisition of motor skills due to hypotonia, joint laxity and the difficulty in balancing a large head with a normal trunk and short limbs.

Patients may also present thoracolumbar kyphosis, lumbar hyperlordosis, recurrent otitis that can cause deafness and dental crowding. Later, deformities in the limbs may occur, such as incurvation (genu varus) or inwardly pointing feet (internal tibial torsion). Additionally, abnormalities in the skull and spine can cause a narrowing of the spinal canal with compression of neurological structures and clinical pain or a functional deficit in the limbs. The final average height achieved for people with achondroplasia is 131 cm in men and 124 cm in women.

Treatment of achondroplasia

The treatment of achondroplasia is focused on the correction of the three main skeletal disorders of the disease: dwarfism, deviations of limbs and deformity of the spine. Dwarfism is treated by bone elongation since the use of growth hormone has not provided benefits in these patients. Bone lengthening is performed in lower limbs with the aim of achieving a final height of about 150 cm, and in the humerus to facilitate personal care. The process may take more than two years and is not without complications. Limb deviations may require young children to wear orthoses, but the older or adolescent child will require bone surgery. Column deformities may require the wearing of a corset or surgery, especially if signs of neurological compression appear. Currently, research is underway to find ways to control the genetic disorder of the disease, although this type of therapy is under development.