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Acrodysostosis

Synonyms of Acrodysostosis

  • Peripheral Dysostosis-Nasal Hypoplasia-Mental Retardation
  • PNM

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Acrodysostosis is an extremely rare skeletal disorder characterized by abnormally short and malformed bones of the hands and feet (peripheral dysostosis) and underdevelopment of the nose (nasal hypoplasia). Other findings may include progressive growth delays, short stature, and/or unusual head and facial (craniofacial) features. Affected infants may exhibit premature maturation of bones of the hands and feet, malformation and shortening of the forearm bones (radius and ulna) near the wrist, and/or abnormally short fingers and toes (brachydactyly). Characteristic facial features may include a flattened, underdeveloped (hypoplastic) "pug" nose, an underdeveloped upper jaw bone (maxilliary hypoplasia), widely spaced eyes (ocular hypertelorism), and/or an extra fold of skin on either side of the nose that may cover the eyes' inner corners (epicanthal folds).

Acrodysostosis is usually accompanied by moderate mental retardation and learning difficulties. It may be inherited as an autosomal dominant trait in some cases, although no gene has yet been identified with this disorder. Acrodysostosis seems to be associated in some cases with advanced parental age.

Symptoms

Acrodysostosis is an extremely rare disorder that is apparent at birth (congenital). It is characterized by abnormally short, malformed hands and feet (peripheral dysostosis), moderate mental retardation, and an underdeveloped flat, short nose (nasal hypoplasia). Affected children are subject to frequent middle ear infections. About 65 to 70% of affected children are hard of hearing.

In infants with this disorder, the hands and feet may appear abnormally short (brachydactyly) at birth due to the shortening and malformation of several bones (peripheral dysostosis) including the metacarpals, metatarsals, and phalanges. In many cases, the end portions (epiphyses) of these bones may be abnormally cone-shaped and/or may harden (ossify) before growth is complete (prematurely). In addition, the bones of the forearms (ulna and radius) may also be abnormally short and malformed . In rare cases, the long bones of the upper arms (humerus) may also develop abnormally. In addition, the fingernails and toenails may be broad and short and/or, in some cases, the bones of the big toe may be overdeveloped (hyperplastic).

Mental retardation is present in about 80% of affected children, but may not be detected until late infancy or childhood. In acrodysostosis, growth retardation may occur before birth (prenatally). Most affected newborns are abnormally small. Growth retardation is typically progressive and usually results in short stature (dwarfism). As children with acrodysostosis age, they may also experience progressively impaired and limited movements of the hands, feet, and/or elbows, and/or pain and swelling (arthritis) in various joints of the body.

In addition, infants with acrodysostosis usually exhibit characteristic abnormalities of the head and facial (craniofacial) area including an underdeveloped (hypoplastic) short "pug" nose with upturned nostrils (anteverted nares) and a flattened low nasal bridge. In addition, affected individuals may exhibit an underdeveloped (hypoplastic) upper jaw bone (maxilla), an abnormally prominent jaw, (prognathism), and/or a tendency to keep the mouth open. Affected individuals may also have widely spaced eyes (ocular hypertelorism); an extra fold of skin on either side of the nose that may cover the eyes' inner corners (epicanthal folds); misaligned teeth (malocclusion), and/or an abnormally short and broad head (brachycephaly).

Causes

The exact cause of acrodysostosis is unknown. Most cases are thought to occur randomly for no apparent reason (sporadically). Some clinical geneticists suggest that, in some cases, acrodys-ostosis may be inherited as an autosomal dominant genetic trait.

Advanced parental age has been noted in fathers of some affected individuals. In acrodysostosis, short stature and shortened hands and feet are caused, in part, by early (premature) maturation of the bones. Abnormal hardening of the ends of the bones (epiphysis) contributes to growth retardation.

Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 11p13" refers to band 13 on the short arm of chromosome 11. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Affected Populations

In reported cases, acrodysostosis has affected females twice as often as males, although theoretically males and females should be affected in equal numbers. Between 40 and 50 cases have been reported in the medical literature.

Related Disorders

Symptoms of the following disorder can be similar to those of acrodysostosis. Comparisons may be useful for a differential diagnosis:

Albright hereditary osteodystrophy is a rare genetic disorder characterized by short stature, abnormally short fingers and/or toes (brachydactyly), mild to moderate mental retardation, and/or the development of bony growths (osseous plaques) on the surface of the skin. These bony growths may spread to the lower levels of skin tissues (subcutaneous ossification). Calcium deposits are also seen on the basal ganglia. Other symptoms may include obesity, abnormally low levels of calcium in the blood (hypocalcemia), and/or the clinical features of hypoparathyroidism. Symptoms of hypoparathyroidism may include seizures, weakness, muscle cramps, excessive nervousness, headaches, and/or tingling, burning, and numbness of the hands. Albright hereditary osteodystrophy is thought to be inherited as an autosomal dominant genetic trait with a 2:1 female to male ratio.

Standard Therapies

Diagnosis
The diagnosis of acrodysostosis may be suspected at birth and may be confirmed during early infancy based upon a thorough clinical evaluation, characteristic physical findings, and the results of specialized imaging techniques. X-ray studies may reveal abnormally short bones in the hands and feet and premature fusion of the end portions (epiphyses) of certain bones of the hands, feet, and elbows. The appearance of spots on the epiphyses (stippling) may also be detected by X-ray. Such skeletal abnormalities, as well as characteristic facial features, are usually present at birth (congenital).

Mental retardation is very common, but may not be detected until late infancy or early childhood. Clinical evaluation should be conducted early in development and on a continuing basis to help determine the extent of mental retardation. Such evaluation can help ensure that appropriate steps are taken to help affected individuals reach their potential.

The clinical features of acrodysostosis are similar to those of Albright hereditary osteodystrophy; so much so that numbers of cases of each have been diagnosed as the other. In Albright hereditary osteodystrophy there is a pronounced loss of activity of certain proteins essential for cellular and hormonal functions. The activity of these proteins is normal in acrodysostosis.

Treatment
The treatment of acrodysostosis is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians; specialists who diagnose and treat skeletal abnormalities (orthopedists); specialists who diagnose, prevent, and/or treat abnormalities of the teeth (orthodontists); physical therapists; and other health care professionals may need to systematically and comprehensively plan an affected child's long-term treatment.

Specific therapies for the treatment of acrodysostosis are symptomatic and supportive. Surgery may be performed to correct underdeveloped (hypoplastic) and/or abnormally prominent jaws (prognathism). In some cases, dental braces may be required to correct misaligned teeth (malocclusion). In addition, in some cases, physical therapy may also be required.

Early intervention is important to ensure that children with acrodysostosis reach their full potential. Special services that may be beneficial to affected children may include special remedial education, social support, and/or other medical, social, and/or vocational services.

Genetic counseling will be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com

Organizations related to Acrodysostosis

(Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder [e.g., short stature, craniofacial abnormalities, etc.].)

References

TEXTBOOKS
Trmbath RC, Amin K. Acrodysostosis. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:146.

Gorlin RJ, Cohen MMJr, Levin LS, eds. Syndromes of the Head and Neck. 3rd ed. Oxford University Press, London, UK; 1990:139-42.

Jones KL, ed. Smith's Recognizable Patterns of Human Malformation. 5th ed. W. B. Saunders Co., Philadelphia, PA; 1997:444-45.

JOURNAL ARTICLES
Giedion A. Acrodysostosis and craniofacial conodysplasia are two separate bone dysplasias. Pediatr Radiol. 2002;32:214.

Albanese A, Hall C, Stanhope R. The use of a computerized method of bone age assessment in clinical practice. Horm Res. 1995;44 Suppl 3:2-7.

Davies SJ, Hughes HE. Familial acrodysostosis: can it be distinguished from Albright's hereditary osteodystrophy? Clin Dysmorphol. 1992;1:207-15.

Steiner RD, Pagon RA. Autosomal dominant transmission of acrodysostosis. Clin Dysmorphol. 1992;1:201-06.

FROM THE INTERNET
Stewart DR. Acrodysostosis, Medical Encyclopedia. MedlinePlus. Update Date: 1/30/2003.
www.nlm.nih.gov/medlineplus/ency/article/001248.htm

Acrodysostosis. Multiple Congenital Anomaly/Mental retardation (MCA/MR) Syndromes. nd. 2pp.
www.nlm.nih.gov/cgi/jablonski/syndrome_cgi?index=5

Acrodysostosis. Orphanet. nd. 1pp.
www.orpha.net/concor/cgi-bin/OC_Exp.php?Lng=GB&Expert=950

McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Acrodysostosis. Entry Number; 101800: Last Edit Date; 3/18/2004.

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Report last updated: 2008/04/25 00:00:00 GMT+0

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