Hypochondroplasia (HCH) is a developmental disorder caused by an autosomal dominant genetic defect in the fibroblast growth factor receptor 3 gene (FGFR3) that results in a disproportionately short stature, micromelia and a head that appears large in comparison with the underdeveloped portions of the body. It is classified as short-limbed dwarfism. Signs and symptoms Individuals affected by this disorder appear normal at birth. As the infant grows, however, their arms and legs do not develop properly, and their body becomes thicker and shorter than normal. The following are characteristics consistent with this condition: Brachydactyly Short stature Micromelia Skeletal dysplasia Abnormality of femur Cause Hypochondroplasia is inherited as an autosomal dominant trait affecting the FGFR3 gene on chromosome 4p16.3. There is currently no cure for this condition. Pathophysiology This disorder results from mutations in the proximal tyrosine kinase domain of the FGFR3 gene. This gene plays an important role in embryonic development, helping to regulate activities such as cell division, migration and differentiation. Hypochondroplasia can be caused by point mutations such as p. Lys650Asn. In FGFR3, some 20 different mutations have been associated with hypochondroplasia, and it seems to have a role in skeletal dysplasia. Diagnosis The diagnosis of this condition can be done via X-rays (with lack of normal distance L1 to L5), and additionally genetic testing is available to ascertain hypochondroplasia. However, the physical characteristics are one of the most important in determining the condition. Treatment Treatment of hypochondroplasia usually takes the form of orthopedic surgery and physical therapy. Genetic counseling is advised for individuals and their families. Specifically in the case of spinal stenosis, one option is laminectomy. Prognosis Life expectancy for individuals with hypochondroplasia is normal; height is about . See also Achondroplasia List of congenital disorders References Further reading External links Skeletal system Growth disorders Cell surface receptor deficiencies Autosomal dominant disorders Rare diseases