Hypochondroplasia 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 when compared with the underdeveloped portions of the body. It is also known as "achondroplasia tarda" and "atypical achondroplasia." Jump to: navigation, search An autosomal dominant gene is an abnormal gene on one of the autosomal (non-sex determining) chromosomes. ... A fibroblast is a cell that makes the structural fibers and ground substance of connective tissue. ... Growth factor is any of about twenty small proteins that attach to specific receptors on the surface of stem cells in bone marrow and promote differentiation and maturation of these cells into morphotic constituents of blood. ... Receptor may refer to: In telecommunication, a receiver. ...

Features

People affected by this disorder appear normal at birth. As the infant grows, however, his/her arms and legs do not develop properly and their body becomes thicker and shorter than normal. The head is normal but appears large due to the underdevelopment of other parts of the body, a symptom called "relative macrocephaly." Cephalic disorders are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system. ...

The clinical and radiographic features of this disorder are milder than those seen in achondroplasia. Achondroplasia is a type of genetic disorder that is a common cause of dwarfism. ...

Intelligence is usually normal.

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, playing a part in regulating activities such as cell division, migration, and differentiation. Tyrosine kinases are a subclass of protein kinase, see there for the principles of protein phosphorylation A tyrosine kinase (EC 2. ... Embryogenesis is the process by which the embryo is formed and develops. ...

Treatment

Standard treatment of hypochondroplasia usually takes the form of orthopedic surgery and physical therapy. Genetic counseling is advised for patients and their families. Jump to: navigation, search Wikimedia Commons has more media related to: Orthopedic corset Orthopedic surgery or orthopedics (BE: orthopaedics) is the branch of surgery concerned with acute, chronic, traumatic, and recurrent injuries and other disorders of the musculoskeletal system, its muscular and bone parts. ... Physical therapy (also known as physiotherapy) is a health profession concerned with the assessment, diagnosis, and treatment of disease and disability through physical means. ... Jump to: navigation, search Genetic counseling generally refers to prenatal counseling done when a genetic condition is suspected in a pregnancy. ...

Etiology

This disorder is transmitted as an autosomal dominant trait affecting the FGFR3 gene on chromosome 4p16.3. Jump to: navigation, search An autosomal dominant gene is an abnormal gene on one of the autosomal (non-sex determining) chromosomes. ... Jump to: navigation, search Figure 1: Chromosome. ...

Epidemiology

Females tend to be affected more often than males.

See also

• Achondroplasia

Achondroplasia is a type of genetic disorder that is a common cause of dwarfism. ...

References

• "Hypochondroplasia." Physician's Guide to Rare Diseases, 2nd ed. (1995). ISBN 0-9628716-1-3
• Mueller, Robert F. and Ian D. Young. Emery's Elements of Medical Genetics, 11th ed. ISBN 0-443-07125-X