Achondroplasia
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What is achondroplasia?
Achondroplasia is a disorder of bone growth. Although achondroplasia literally means without cartilage formation, the problem is not in forming cartilage but in converting it to bone, particularly in the long bones of the arms and legs.
All people with achondroplasia have short stature. The average height of an adult male with achondroplasia is 131 centimeters (4 feet, 4 inches), and the average height for adult females is 124 centimeters (4 feet, 1 inch). Characteristic features of achondroplasia include an average-size trunk, short arms and legs with particularly short upper arms and thighs, limited range of motion at the elbows, and an enlarged head (macrocephaly) with a prominent forehead. Fingers are typically short and the ring finger and middle finger may diverge, giving the hand a three-pronged (trident) appearance. People with achondroplasia are generally of normal intelligence.
Health problems commonly associated with achondroplasia include episodes in which breathing slows or stops for short periods (apnea), obesity, and recurrent ear infections. In adulthood, individuals with the condition usually develop a pronounced and permanent sway of the lower back (lordosis) and bowed legs. Older individuals often have back pain, which can cause difficulty with walking.
How common is achondroplasia?
Achondroplasia is the most common type of short-limbed dwarfism. The condition occurs in 1 in 15,000 to 40,000 newborns.
What genes are related to achondroplasia?
Mutations in the FGFR3 gene cause achondroplasia.
The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. This protein limits the formation of bone from cartilage (a process called ossification), particularly in the long bones. Two specific mutations in the FGFR3 gene are responsible for almost all cases of achondroplasia. Researchers believe that these mutations cause the protein to be overly active, which interferes with skeletal development and leads to the disturbances in bone growth seen with this disorder.
How do people inherit achondroplasia?
Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. About 80 percent of people with achondroplasia have average-size parents; these cases result from a new mutation in the FGFR3 gene. In the remaining cases, people with achondroplasia have inherited an altered FGFR3 gene from one or two affected parents. Individuals who inherit two altered copies of this gene typically have very severe problems with bone growth, and are usually stillborn or die shortly after birth from respiratory failure.
Source: National Institutes of Health
Research from University of Michigan, Medical Department has provided new data on life sciences
2009 JUL 14 - (NewsRx.com) -- "Given the complexity and diversity of congenital differences, a separate and broad category of generalized skeletal abnormalities was proposed to include all conditions that are unable to be neatly packaged into the other categories," scientists writing in the journal Hand Clinics report. "Some of the conditions included in this category are obscure, whereas others are more common. Some conditions listed in this section may fit into other categories but may be considered as part of the overall classification scheme," wrote A.J. Watt and colleagues, University of Michigan, Medical Department. The researchers concluded: "This article presents congenital trigger finger, congenital clasped thumb, Madelung's deformity, and other skeletal hand deformities that are characteristic of generalized bone and connective tissue disorders, including achondroplasia and Marfan syndrome.." Watt and colleagues published their study in Hand Clinics (Generalized Skeletal Abnormalities. Hand Clinics, 2009;25(2):265+). Additional information can be obtained by contacting K.C. Chung, University of Michigan, School Medical, Dept. of Surgery, Sect Plast Surgery, 2130 Taubman Center, 1500 E Med Center Dr., Ann Arbor, MI 48109, USA. The publisher of the journal Hand Clinics can be contacted at: W B Saunders Co-Elsevier Inc., 1600 John F Kennedy Boulevard, Ste. 1800, Philadelphia, PA 19103-2899, USA. Keywords: United States, Ann Arbor, Life Sciences, Orthopedics, Genetics, Achondroplasia, University of Michigan, Medical Department. This article was prepared by Science Letter editors from staff and other reports. Copyright 2009, Science Letter via NewsRx.com.
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