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Achondroplasia in children is the most common form of dwarfism; it accounts for about 70% of all cases of dwarfism. [1] Achondroplasia falls into the category of “disproportionate dwarfism”. It is linked to a mutation in the fibroblast growth factor receptor-3.
Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism. [3] It is the most common cause of dwarfism [4] and affects about 1 in 27,500 people. [3] In those with the condition, the arms and legs are short, while the torso is typically of normal length. [3]
It is believed to be caused by defects of genes on chromosome 3 and 18. One form of Seckel syndrome can be caused by mutation in the gene encoding the ataxia telangiectasia and Rad3-related protein which maps to chromosome 3q22.1–q24. This gene is central in the cell's DNA damage response and repair mechanism. Types include:
Dwarfism occurs in animals as well as humans; horses can have achondroplastic symptoms, as shown here next to a person with dwarfism. All small dog breeds exhibit dwarfism (the standard size of dogs, without interference from humans, is the same as that of the wolves).
It is thought that chondrodystrophy [2] is caused by an autosomal, recessive allele.To avoid a potential "lethal dose", both parents can be genetically tested.If a child is conceived with another carrier the outcome may be lethal, or the child may suffer from chondrodystrophy or dwarfism. [3]
Shortened stature can result from growth hormone deficiency, starvation, portal systemic shunts, renal disease, hypothyroidism diabetes mellitus and other conditions. Any of these conditions can be established in a population through genetic engineering, selective breeding, or insular dwarfism, or some combination of the above.
Joubert syndrome is one such disease. It is a member of an emerging class of diseases called ciliopathies. [22] The underlying cause of the ciliopathies may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body.
Other causes of genu valgum (knock knees) or genu varum (bow legs) such as rickets; Spondyloepiphyseal dysplasia congenita; Radiographic findings of the pelvis and hips found in Perthes disease should not be confused with pseudochondroplasia. Patients with Perthes disease may present with unilateral hip affection.