Achondroplasia is a significant genetic disorder of the bone. The word achondroplasia actually means 'without cartilage'. It is a congenital abnormality. The condition of achondroplasia is marked by disproportional development of bones resulting in defects affecting the appearance of a person. Achondroplasia predominantly occurs in infants because of the inheritance of genes associated with skeletal dysplasia also known as short stature syndrome.
The incidence of achondroplasia is dependent on the fibroblast growth factor receptor 3 (FGFR3) protein which is responsible for bone development. The faulty coding of FGGR-3 produced by the FGFR3 gene results in achondroplasia. The inheritance of the faulty gene FGFR3 in a family resulting in achondroplasia is called as autosomal dominant inheritance. The primary defect of this condition is caused because of the abnormal chondrocyte proliferation at the growth plate region. This proliferation process results in the formation of short and proportionately thick and long bones.
The manifestation of this is predominantly seen in the proximal regions such as large head because of intramembranous ossification, lumbar lordosis and saddle nose appearance (mid face hypoplasia). In case of severe spinal deformity, cord compression is noticed. The achondroplastic disorder pertaining to the homozygous nature is more lethal in infants than the sporadic form. Other cases such as pseudoachondroplasia resemble achondroplasia but it does not have skull abnormalities.
Diagnosis and treatment
The diagnosis of achondroplasia is usually done at an early stage. The child is examined for abnormalities affecting bone development. Gene assays are also done to detect the presence of the FGFR-3 mutated genes. In many cases congenital anomalies are also considered a diagnostic measure.
Corrective treatment measures are taken in children who are susceptible to achondroplasia. The child is monitored on a regular basis to identify the abnormalities in bone development and growth processes. Emphasis during observation and treatment is given to the development of head and spine to notice conditions such as hydrocephalus and foramen magnum abnormalities. In case of hydrocephalus, the neurosurgeon drains out the excess fluid through a shunt to reduce the pressure caused to the brain.
Abnormalities of spinal cord are very significant factors determining the onset of cord compression. Some of the characteristic features of spinal cord compression include snoring, sleep apnea in infants and also reduced muscle tone. In such cases, the fluid is drained to reduce the pressure on the spinal cord. Where there is occurrence of Kyphosis, also known as small hump, surgical intervention is done to rectify the condition. Other significant procedures involve drainage from ears to prevent infections and also dental procedures to reduce overcrowding of teeth.
Bibliography / Reference
Collection of Pages - Last revised Date: February 17, 2019