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Achondroplasia, in human physiology, is a type of inherited dwarfism that results in a large head and short limbs.

Achondroplasia is caused by a simple dominant gene. However, inheriting the achondroplasia gene from both parents will result in a stillborn child. In about 80% of cases, the condition results from a mutation in the offspring of two genetically normal parents.

New gene mutations are associated with increasing paternal age (over 35 years). Studies have demonstrated that new gene mutations are exclusively inherited from the father and occur during spermatogenesis (as opposed to resulting from a germline mosaicism).

See also: List of rare diseases

Growth hormone (GH) therapy has been proposed as a possible treatment for the short stature of achondroplasia. 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. Early experience with surgical limb lengthening procedures resulted in a high incidence of complications, but recent experiences have improved results considerably.

For the genetic details: More than 99% of achondroplasia is caused by two different mutations in the fibroblast growth factor receptor 3 (FGFR3). In about 98% of cases, the mutation is a Gly380Arg substitution, resulting from a G to A point mutation at nucleotide 1138 of the FGFR3 gene [Bellus et al 1995, Shiang et al 1994, Rousseau et al 1996]. About 1% of cases are caused by a G to C point mutation at nucleotide 1138.