Chromosome 9 Ring

Chromosome 9 Ring

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Chromosome 9 Ring is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • Ring 9
  • Ring 9, Chromosome
  • R9

Disorder Subdivisions

  • None

General Discussion

Chromosome 9 Ring is a rare disorder in which there is loss (deletion) of chromosomal material from both ends of the 9th chromosome and joining of the ends to form a ring. Associated symptoms and findings may vary, depending upon the amount and location of lost chromosomal material and other factors. Some affected individuals may have variable malformations of the skull and facial (craniofacial) region. However, in others with the chromosomal abnormality, such features may not be apparent. Chromosome 9 Ring may also be characterized by additional physical features in some cases, including growth retardation, heart defects, genital abnormalities, and/or other findings. In addition, many affected individuals have moderate to severe mental retardation; however, in some instances, intelligence may be in the low normal range. Chromosome 9 Ring usually appears to result from spontaneous (de novo) errors very early in the development of the embryo that occur for unknown reasons (sporadically).

Symptoms

As noted above, Chromosome 9 Ring may be characterized by various craniofacial malformations; however, in some cases, such features may not be apparent. Craniofacial defects associated with Chromosome 9 Ring may include an abnormally small head (microcephaly) and/or premature fusion of the fibrous joint (suture) between bones forming the forehead (metopic suture), resulting in an unusually narrow, pointed, "triangular" or "keel-shaped" forehead (trigonocephaly) and closely spaced eyes (ocular hypotelorism). Some affected individuals may also have abnormally slanting eyelid folds (palpebral fissures), slight protrusion of the eyes (exophthalmos), an exaggerated arch to the eyebrows, a small jaw (micrognathia) and small chin, and/or a short neck.



In some cases, Chromosome 9 Ring may also be associated with growth retardation after birth; various structural malformations of the heart (congenital heart defects), such as an abnormal opening in the partition (septum) that normally separates the lower chambers (ventricles) of the heart (ventricular septal defect); and/or variable skeletal abnormalities. Some affected males may also have genital abnormalities, including ambiguous genitalia or abnormal placement of the urinary opening (hypospadias), such as on the underside of the penis. Additional physical abnormalities have also been reported in association with Chromosome 9 Ring. These have included incomplete closure of the roof of the mouth (cleft palate); abnormal bending (clinodactyly) of certain fingers; a single crease across the palms of the hands; and/or a condition known as gastroesophageal reflux. The latter is characterized by abnormal backflow (reflux) of stomach acid into the esophagus, causing inflammation of and possible damage to the esophageal lining.



Chromosome 9 Ring is commonly characterized by moderate to severe mental retardation. However, some affected individuals may have intelligence in the low normal range. Those with the disorder may also show variable delays in the acquisition of skills requiring the coordination of mental and physical activities (psychomotor retardation) and/or behavioral abnormalities, such as agitated or withdrawn, introverted behavior.

Causes

Chromosome 9 Ring is caused by deletion of chromosomal material from the end (distal) regions of the short arm (p) and long arm (q) of chromosome 9 and joining of the ends to form a ring. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as "p", a long arm identified by the letter "q" and a narrowed region at which the two arms are joined (centromere). Chromosomes are further subdivided into bands that are numbered outward from the centromere.



As noted above, in those with Chromosome 9 Ring, associated symptoms and findings may vary from case to case. Such clinical variability may depend upon the amount and specific location of material lost from the 9th chromosome, the stability of the ring chromosome during subsequent cellular divisions, and/or other factors. For example, in some cases, only a certain percentage of an affected individual's cells may have Chromosome 9 Ring, while other cells may have a normal chromosomal makeup (a finding known as "chromosomal mosaicism"), affecting the variability of associated symptoms and physical features.



Chromosome 9 Ring usually appears to be caused by spontaneous (de novo) errors very early during embryonic development. In such instances, the parents of the affected child usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality. However, it is theoretically possible that a parent of an affected individual also has Chromosome 9 Ring in all or some cells with few apparent symptoms. In such instances, it is believed that Chromosome 9 Ring may have been inherited and that the chances are greater of having another child with the chromosomal abnormality.



Chromosomal analysis and genetic counseling are typically recommended for parents of an affected child to help confirm or exclude the presence of certain chromosomal abnormalities in one of the parents, such as Chromosome 9 Ring, mosaicism, or a balanced chromosomal rearrangement involving chromosome 9.

Affected Populations

Chromosome 9 Ring is a rare chromosomal abnormality that is thought to affect males and females in relatively equal numbers. Since the disorder was originally described, more than 12 cases have been reported in the medical literature.

Standard Therapies

Diagnosis

In some instances, Chromosome 9 Ring may be suggested before birth (prenatally) by specialized tests such as ultrasound, amniocentesis, and/or chorionic villus sampling (CVS). During fetal ultrasonography, reflected sound waves create an image of the developing fetus, potentially revealing certain findings that suggest a chromosomal disorder or other developmental abnormalities. With amniocentesis, a sample of fluid that surrounds the developing fetus is removed and analyzed, while CVS involves the removal of tissue samples from a portion of the placenta. Chromosomal analysis performed on such fluid or tissue samples may reveal the presence of Chromosome 9 Ring.



In most cases, Chromosome 9 Ring is diagnosed or confirmed after birth (postnatally) based upon a thorough clinical evaluation, characteristic physical findings, and chromosomal analysis. Various specialized tests may also be performed to help detect and/or characterize certain abnormalities that may be associated with the disorder. For example, a thorough cardiac evaluation may be advised to detect any heart abnormalities that may be present. Such evaluations may include a thorough clinical examination, evaluation of heart and lung sounds through use of a stethoscope, and specialized tests that enable physicians to evaluate the structure and function of the heart (e.g., x-ray studies, electrocardiography [EKG]), echocardiography).



Treatment

The treatment of Chromosome 9 Ring is directed toward the specific symptoms that are apparent in each individual. Such disease management may require the coordinated efforts of a team of medical professionals, such as pediatricians; physicians who diagnose and treat disorders of the skeleton, muscles, joints, and related tissues (orthopedists); heart specialists (cardiologists); and/or other health care professionals.



For some affected individuals, physicians may recommend surgical repair or correction of certain craniofacial, genital, and/or other malformations associated with the disorder. In addition, for those with congenital heart defects, treatment with certain medications, surgical intervention, and/or other measures may be required. The specific surgical procedures performed will depend upon the severity and location of the anatomical abnormalities, their associated symptoms, and other factors.



Early intervention may also be important in ensuring that affected children reach their potential. Special services that may be beneficial include special education, speech therapy, physical therapy, and/or other medical, social, and/or vocational services. Genetic counseling will also be of benefit for affected individuals and their families. Other treatment for this disorder 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 web site.



For information about clinical trials being conducted at the NIH Clinical Center 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

References

TEXTBOOKS

Jones KL. Smith's Recognizable Patterns of Human Malformation. 5th ed. Philadelphia, PA: W.B. Saunders Company; 1997:46-47.



Thoene JG, ed. Physicians' Guide to Rare Diseases. Montvale, NJ: Dowden Publishing Company Inc; 1995:33.



Buyse ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:354.



JOURNAL ARTICLES

Seghezzi L, et al. Ring chromosome 9 with a 9p22.3-p24.3 duplication. Eur J Pediatr. 1999;158:791-93.



Cavaliere ML, et al. Phenotypic variability in the chromosome 9 ring. Acta Biomed Ateneo Parmense. 1997;68(suppl 1):85-89.



Lanzi G, et al. Ring chromosome 9: an atypical case. Brain Dev. 1996;18:216-19.



Kontiokari T, et al. Ring chromosome 9. Duodecim. 1995;111:439-41.



Blennow E, et al. Characterization of supernumerary ring marker chromosomes by fluorescence in situ hybridization (FISH). Am J Hum Genet. 1993;53:433-42.



Manouvrier-Hanu S, et al. Another case of ring chromosome 9 associated with gastroesophageal reflux [letter]. Am J Med Genet. 1989;32:558.



Manouvrier-Hanu S, et al. Ring chromosome 9. Case report and review of the literature. Ann Genet. 1988;31:250-53.



Leung AK, et al. A case of ring (9)/del(9p) mosaicism associated with gastroesophageal reflux. Am J Med Genet. 1988;29:43-48.



Fryns JP, et al. Moderate mental retardation and nonspecific dysmorphic syndrome associated with ring chromosome 9. Hum Genet. 1979;50:29-32.

Resources

Children's Craniofacial Association

13140 Coit Road

Suite 517

Dallas, TX 75240

USA

Tel: (214)570-9099

Fax: (214)570-8811

Tel: (800)535-3643

Email: contactCCA@ccakids.com

Internet: http://www.ccakids.com



March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

Tel: (914)997-4488

Fax: (914)997-4763

Tel: (888)663-4637

Email: Askus@marchofdimes.com

Internet: http://www.marchofdimes.com



The Arc

1825 K Street NW, Suite 1200

Washington, DC 20006

Tel: (202)534-3700

Fax: (202)534-3731

Tel: (800)433-5255

TDD: (817)277-0553

Email: info@thearc.org

Internet: http://www.thearc.org



AmeriFace

P.O. Box 751112

Limekiln, PA 19535

USA

Tel: (702)769-9264

Fax: (702)341-5351

Tel: (888)486-1209

Email: info@ameriface.org

Internet: http://www.ameriface.org



Chromosome Disorder Outreach, Inc.

P.O. Box 724

Boca Raton, FL 33429-0724

USA

Tel: (561)395-4252

Fax: (561)395-4252

Email: info@chromodisorder.org

Internet: http://www.chromodisorder.org/CDO/



American Heart Association

7272 Greenville Avenue

Dallas, TX 75231

Tel: (214)784-7212

Fax: (214)784-1307

Tel: (800)242-8721

Email: Review.personal.info@heart.org

Internet: http://www.heart.org



Chromosome 9P- Network

P.O. Box 524

Appleton, WI 54912

USA

Email: 9pminusinfo@gmail.com

Internet: http://www.9pminus.org



UNIQUE - Rare Chromosome Disorder Support Group

P.O. Box 2189

Caterham

Surrey, CR3 5GN

United Kingdom

Tel: 4401883330766

Fax: 4401883330766

Email: info@rarechromo.org

Internet: http://www.rarechromo.org



Craniofacial Foundation of America

975 East Third Street

Chattanooga, TN 37403

Tel: (423)778-9176

Fax: (423)778-8172

Tel: (800)418-3223

Email: terry.smyth@erlanger.org

Internet: http://www.craniofacialfoundation.org



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

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