Achondroplasia

Achondroplasia is the most distinctive birth defect, which is mainly the cause of short stature with disproportionately short limbs. This disorder can also be defined as the growth of cartilage in the long bones and skull that result in premature ossification. Achondroplasia is the autosomal dominant trait, which means that if a baby gets the defective gene from one parent, the child will have the disorder. People with this condition have short stature, usually reaching a full adult height of around 4'0" (1.22 meters). An individual with achondroplasia who has a reproductive partner with normal stature has a 50% risk in each pregnancy of having a child with achondroplasia. Adults usually reach a height of between 42 and 56 inches. The head is large and the forehead is prominent. Portions of the face can be underdeveloped as well.

Achondroplasia is a disorder of bone growth. Although achondroplasia literally means "without cartilage formation," the problem in achondroplasia is not in forming cartilage but in converting it to bone, particularly in the long bones. In fact, we can say that Achondroplasia is the type of dwarfism in humans which can be inherited as an autosomal dominant phenotype. This diseases occurs when a spontaneous mutation (a sudden genetic defect) that does in the developing embryo. The schedule to which an achondroplastic child's development should be compared is not that for all children in the general population, but rather the timetable followed by achondroplastic children. Hypochondroplasia is a milder form of achondroplasia which presents in late childhood. The offspring of two achondroplasts may produce a hereditary form of the disease known as homozygous achondroplasia. This is a lethal form of the disease in the neonatal period. 

Achondroplasia dwarfism & its inheritance

Achondroplasia is a disorder of bone growth that causes the most common type of dwarfism. Achondroplasia is the most common form of short-limb dwarfism, a developmental disorder in which bone tissue does not develop properly in the long bones of the arms and legs. Achondroplasia is usually diagnosed at birth, owing to the characteristic appearance of the newborn. People with achondroplasia have abnormally short arms and legs. Their trunk is usually of normal size, as is their head. The appearance of short limbs and normal head size actually makes the head appear to be oversized.

Cause of Achondroplasia

Achondroplasia is mainly an inherited diseases occurs in the young age which causes an abnormality of cartilage formation. It occurs at a frequency of about 1 in 20,000 to 1 in 40,000 births. The genetic defect lies at the fibroblast growth factor-3 gene, but in a different location than thanatophoric dwarfism. baby with achondroplasia has a relatively long, narrow torso (trunk) with short extremities (arms and legs) and a disproportionate shortening of the proximal (near the torso) segments of the limbs (the upper arms and thighs). The disorder is a result of an autosomal dominant mutation in the fibroblast growth factor receptor gene 3 (FBFR3), which causes an abnormality of cartilage formation. This results in defective endochondral bone formation with resultant shortening of tubular bones. The shaft caliber is less affected because periosteal intramembraneous bone formation is not affected. In this particular condition, a protein in the body called the "Fibroblast Growth Factor Receptor" begins to function abnormally.

Symptoms of Achondroplasia

Achondroplasis is genetic disorder of bone growth which runs in families, therefore the family history of achondroplasia should alert parents to the possibility of having an affected child. Suspect possible cervicomedullary compression with a history of pain, ataxia, incontinence, and apnea. Cord compression may result in respiratory arrest and progressive quadriparesis. No matter whether a person with achondroplasia carries a new or an "old" gene, the risk for passing that gene down to a child is 50%. It is 50% with each pregnancy, irrespective of the outcome of prior pregnancies. It is like flipping a coin each time. Given below are the list of some possible symptoms:

• Short stature
• Short limbs (upper arm and thigh)
• Skeletal (limb) abnormalities
• Abnormal hand appearance (trident hand) with persistent space between the long and ring fingers
• Marked kyphosis and lordosis (spine curvatures)
• Waddling gait
• Prominent (conspicuous) forehead ( frontal bossing )
• Disproportionately large head-to-body size difference
• Hypotonia
• Polyhydramnios
• Bowed legs
• Spinal stenosis

Treatment of Achondroplasia

The only form of prevention is through genetic counseling , which could help parents assess their risk of having a child with achondroplasia. Surgery can also be used to prevent spinal compression and correct bowed legs. Treatment of achondroplasia primarily addresses some of the complications of the disorder, including problems due to nerve compression, hydrocephalus, bowed legs, and abnormal curves in the spine. Related abnormalities, including spinal stenosis and spinal cord compression, should be treated when they cause problems.Different Methods for treating Achondroplasia are :

• Related abnormalities, including spinal stenosis and spinal cord compression, should be treated when they cause problems.
• Surgery is sometimes needed to correct specific skeletal deformities.
• In children with signs of craniomedullary compression, surgical treatment to release the compression can improve neurologic, cognitive, and respiratory functions.
• However, the people who participated in the studies on the subject have not yet reached adult size, so this type of therapy has unknown results.
• Surgical decompression of the cord is needed to relieve the pressure on it. This is done by opening the canal at the affected levels in a procedure called a "laminectomy."
• Knowledgeable pediatric care and periodic orthopedic and neurologic examinations are critical.
• Pregnant women with achondroplasia should have their babies delivered by cesarean birth.

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