Summitt Syndrome

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Summitt Syndrome 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.


  • Summitt's Acrocephalosyndactyly

Disorder Subdivisions

  • None

General Discussion

Summitt syndrome is an extremely rare genetic disorder characterized by malformations of the head, abnormalities of the hands and/or feet, and obesity. The syndrome is inherited as an autosomal recessive genetic trait. Some researchers believe that Summitt syndrome is one of seven closely related forms of a disorder characterized by characteristic malformations of the head and webbing between several toes and/or fingers (acrocephalopolysyndactyly). The malformations of the head are the result of the premature closings of the seams (cranial sutures) between the bony plates that make up the skull. Of the various forms of this disorder, many geneticists believe that Summitt syndrome is closely related to Carpenter syndrome (acrocephalopolysyndactyly type II).


In Summitt syndrome, the fibrous joints between the bones in the skull (cranial sutures) close prematurely (craniosynostosis), causing the head to grow upward at an accelerated rate. As a result, the head appears long, narrow, and pointed at the top (tower skull). Affected individuals also have webbed or fused fingers and/or toes (syndactyly) and are usually extremely overweight (obese). Other features may include vertical folds of skin over the eyes' inner corners (epicanthal folds), delayed tooth eruption, an abnormally narrow roof of the mouth (palate), a malformed hip joint (coxa valga), and/or knock knees, that is, knees that are abnormally close together and ankles that are abnormally wide apart (genu valgum). Males with Summitt syndrome may have an abnormal enlargement of one or both breasts (gynecomastia). Intelligence is typically within normal limits.


Summitt syndrome is inherited as an autosomal recessive trait. The precise location of the changed gene has not yet been determined.

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.

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 a few 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.

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.

Affected Populations

Summitt syndrome is an extremely rare disorder that is believed to affect males and females in equal numbers. There have been too few cases reported to determine whether the disorder is more prevalent among males or females. The number of affected individuals is thought to number only about 12, of whom at least two were the children of closely related parents.

Standard Therapies

Summitt syndrome can be detected at birth, based upon a clinical evaluation and characteristic physical findings. Surgical correction of malformations is the primary treatment. Early craniofacial surgery may be performed to correct the premature closure of the bones in the skull (craniosyn-ostosis). Additional craniofacial surgery may be done later in life as well as surgery to correct deformities of the hands and/or feet.

Other treatment is symptomatic and supportive. Genetic counseling will be of benefit for people with Summitt syndrome and their families.

Investigational Therapies

Information on current clinical trials is posted on the Internet at 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


For information about clinical trials sponsored by private sources, contact:



Buyce ML. Editor-in-Chief. Birth Defects Encyclopedia. Blackwell Scientific Publications. Center for Birth Defects Information Services, Inc., Dover, MA; 1990:36.

Magalini SI, Magalini SC, de Franscisi G., eds. Dictionary of Medical Syndromes. 3rd Ed. JB Lippincott Co. Philadelphia, PA. 1990:850


Pierquin G, Seligmann R, Van Regemorter N. Familial Occurrence of Summitt syndrome or a variant example of Carpenter syndrome. Genet Couns.1992;3:101-05.

Gershoni-Baruch R. Carpenter syndrome: marked variability of expression to include the Summitt and Goodman syndromes. Am J Med Genet. 1990;35:236-40.

Cohen DM, Green JG, Miller J, et al. Acrocephalopolysyndactyly type II - Carpenter syndrome: clinical spectrum and an attempt at unification with Goodman and Summitt syndromes. Am J Med Genet. 1987;28:311-24.

Sells CJ, Hanson JW, Hall JG. The Summitt syndrome: observations on a third case. Am J Med Genet. 1979;3:27-33.


McKusick VA, ed. Online Mendelian Inheritance In Man (OMIM). The Johns Hopkins University. Summitt Syndrome. Entry Number; 272350: Last Edit Date; 12 March 1994.

Acrocephalopolysyndactyly. Amershamhealth. nd. 1p.

Moorhead JC. Craniosynostosis Syndromes. Ground Round Archives, Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine. June 24, 1993. 4pp.

Acrocephalosyndactyly (Carpenter's Syndrome). Birth Disorder Information Directory (BDID). nd. 1p.


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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 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