What is achondroplasia?

Achondroplasia or dwarfism is a genetic disorder that affects bone growth. Dr. Galo García Fontecha, author of the article, is a renowned researcher and specialist in Pediatric Traumatology and Orthopedic Surgery, expert in all traumatic, congenital or developmental pathologies of the locomotor system in children. He practices at Lenox Corachan and Centro Medico Delfos. Here are all the details about this disorder and how to deal with it.

Achondroplasia is the most common type of a group of diseases called bone dysplasias. These are characterized by a generalized alteration of bone and cartilage tissue and are the most common cause of severe growth retardation (dwarfism). Achondroplasia is usually suspected on routine ultrasound scans in the third trimester of pregnancy due to the presence of short bones in the extremities. It can be confirmed at that time with genetic and molecular testing. It is sometimes diagnosed at birth by physical features of dwarfism and by radiological features.

Causes of achondroplasia

Achondroplasia is caused by a genetic mutation that affects bone formation (specifically the so-called endochondral ossification). The genetic disorder is transmitted in an autosomal dominant manner, although in 80% of cases the mutation occurs “de novo”, i.e. without the parents being affected.

Achondroplasia, symptoms or characteristics

At birth, babies with achondroplasia have a typical appearance of limbs disproportionately short in relation to the trunk and a large head with depressed nasal bridge and prominent jaw.

Achondroplasia dwarfism is characterized by affecting the limb segments closest to the trunk, humeri and femurs. Other features include thick skin folds with the appearance of excessive muscle tissue, global hypotonia with marked laxity of the joints except for the elbow which is usually limited in stretching, short hands with marked separation between the middle and ring fingers (“trident” deformity) and with the three central fingers of the same length (“starfish” deformity).

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During growth they present a delay in the acquisition of motor skills due to the sum of hypotonia, joint laxity and difficulty in balancing a large head with a normal trunk and short limbs.

They may also present thoracolumbar kyphosis, lumbar hyperlordosis, recurrent otitis that can lead to deafness and dental crowding. Later on, deformities in the extremities may appear, such as incurvation (genu varum) or inward feet (internal tibial torsion).

The alterations in the skull and spine can cause a narrowing of the spinal canal with compression of the neurological structures and painful symptoms or functional deficits in the extremities.

The average final height achieved in people with achondroplasia is 131 cm in men and 124 cm in women.

The radiological study shows characteristic features and confirms the disease. The facial bones are poorly formed, the vertebrae are short, the pelvis is short and rounded, the area of the pelvis where the hip articulates is flattened, there may be lumbar vertebral wedging, the bones of the extremities are short except for the fibula, the radial head is deformed and eventually dislocates and the growth area of the femur in the knee is shaped like an inverted “V”.

Treatment of achondroplasia

The treatment of achondroplasia is focused on the correction of the three main skeletal disorders of the disease: dwarfism, limb deviations and spinal deformity.

Dwarfism is treated by bone elongation since the use of growth hormone has not been beneficial in these patients. Bone lengthening is performed in the lower extremities with the aim of achieving a final height of about 150 cm, and in the humerus to facilitate self-care. The process can take more than two years and is not without complications.

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Limb deviations may require bracing in the young child, but in the older child or adolescent will require bone surgery.

Spinal deformities may require bracing or surgery, especially if there are signs of neurological compression.

Research is currently underway to control the genetic disorder of the disease, although this type of therapy is in the developmental stage.

Prognosis of achondroplasia

Children with achondroplasia have a higher perinatal mortality rate. However, after this stage, life expectancy is similar to that of the general population, although the presence of orthopedic problems means that they are likely to undergo bone surgery during their lifetime.

These patients have a normal IQ and their global health parameters are not significantly diminished.