Skip Navigation
Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

Cohen syndrome

Reviewed January 2008

What is Cohen syndrome?

Cohen syndrome is an inherited disorder that affects many parts of the body and is characterized by developmental delay, intellectual disability, small head size (microcephaly), and weak muscle tone (hypotonia). Other features include progressive nearsightedness (myopia), degeneration of the light-sensitive tissue at the back of the eye (retinal dystrophy), an unusually large range of joint movement (hypermobility), and distinctive facial features. Characteristic facial features include thick hair and eyebrows, long eyelashes, unusually-shaped eyes (down-slanting and wave-shaped), a bulbous nasal tip, a smooth or shortened area between the nose and the upper lip (philtrum), and prominent upper central teeth. The combination of the last two facial features results in an open-mouth appearance.

The features of Cohen syndrome vary widely among affected individuals. Additional signs and symptoms in some individuals with this disorder include low levels of white blood cells (neutropenia), overly friendly behavior, and obesity that develops in late childhood or adolescence. When obesity is present, it typically develops around the torso, with the arms and legs remaining slender. Individuals with Cohen syndrome may also have narrow hands and feet, and slender fingers.

How common is Cohen syndrome?

The exact incidence of Cohen syndrome is unknown. It has been diagnosed in fewer than 1,000 people worldwide. More cases are likely undiagnosed.

What genes are related to Cohen syndrome?

Mutations in the VPS13B gene (frequently called the COH1 gene) cause Cohen syndrome. The function of the protein produced from the VPS13B gene is unknown; however, researchers suggest it may be involved in sorting and transporting proteins inside the cell. Most mutations in the VPS13B gene are believed to prevent cells from producing a functional VPS13B protein. It is unclear how loss of functional VPS13B protein leads to the signs and symptoms of Cohen syndrome.

Related Gene(s)

Changes in this gene are associated with Cohen syndrome.

  • VPS13B

How do people inherit Cohen syndrome?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of Cohen syndrome?

These resources address the diagnosis or management of Cohen syndrome and may include treatment providers.

  • Gene Review: Cohen Syndrome (
  • Genetic Testing Registry: Cohen syndrome (
  • MedlinePlus Encyclopedia: Hypotonia (

You might also find information on the diagnosis or management of Cohen syndrome in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about Cohen syndrome?

You may find the following resources about Cohen syndrome helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for Cohen syndrome?

  • Hypotonia, obesity, and prominent incisors
  • Norio syndrome
  • obesity-hypotonia syndrome
  • Pepper syndrome
  • prominent incisors-obesity-hypotonia syndrome

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about Cohen syndrome?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding Cohen syndrome?

autosomal ; autosomal recessive ; cell ; developmental delay ; disability ; gene ; hypermobility ; hypotonia ; incidence ; inherited ; joint ; microcephaly ; muscle tone ; myopia ; nearsightedness ; neutropenia ; philtrum ; protein ; recessive ; syndrome ; tissue ; white blood cells

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Gene Review: Cohen Syndrome (
  • Hennies HC, Rauch A, Seifert W, Schumi C, Moser E, Al-Taji E, Tariverdian G, Chrzanowska KH, Krajewska-Walasek M, Rajab A, Giugliani R, Neumann TE, Eckl KM, Karbasiyan M, Reis A, Horn D. Allelic heterogeneity in the COH1 gene explains clinical variability in Cohen syndrome. Am J Hum Genet. 2004 Jul;75(1):138-45. Epub 2004 May 20. (
  • Kolehmainen J, Black GC, Saarinen A, Chandler K, Clayton-Smith J, Träskelin AL, Perveen R, Kivitie-Kallio S, Norio R, Warburg M, Fryns JP, de la Chapelle A, Lehesjoki AE. Cohen syndrome is caused by mutations in a novel gene, COH1, encoding a transmembrane protein with a presumed role in vesicle-mediated sorting and intracellular protein transport. Am J Hum Genet. 2003 Jun;72(6):1359-69. Epub 2003 May 2. (
  • Kolehmainen J, Wilkinson R, Lehesjoki AE, Chandler K, Kivitie-Kallio S, Clayton-Smith J, Träskelin AL, Waris L, Saarinen A, Khan J, Gross-Tsur V, Traboulsi EI, Warburg M, Fryns JP, Norio R, Black GC, Manson FD. Delineation of Cohen syndrome following a large-scale genotype-phenotype screen. Am J Hum Genet. 2004 Jul;75(1):122-7. Epub 2004 May 12. (
  • Seifert W, Holder-Espinasse M, Spranger S, Hoeltzenbein M, Rossier E, Dollfus H, Lacombe D, Verloes A, Chrzanowska KH, Maegawa GH, Chitayat D, Kotzot D, Huhle D, Meinecke P, Albrecht B, Mathijssen I, Leheup B, Raile K, Hennies HC, Horn D. Mutational spectrum of COH1 and clinical heterogeneity in Cohen syndrome. J Med Genet. 2006 May;43(5):e22. (
  • Taban M, Memoracion-Peralta DS, Wang H, Al-Gazali LI, Traboulsi EI. Cohen syndrome: report of nine cases and review of the literature, with emphasis on ophthalmic features. J AAPOS. 2007 Oct;11(5):431-7. Epub 2007 Mar 26. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: January 2008
Published: February 8, 2016