Clouston syndrome is a form of ectodermal dysplasia, a group of about 150 conditions characterized by abnormal development of some or all of the ectodermal structures, which include the skin, hair, nails, teeth, and sweat glands. Specifically, Clouston syndrome is characterized by abnormalities of the hair, nails, and skin, with the teeth and sweat glands being unaffected.

In infants with Clouston syndrome, scalp hair is sparse, patchy, and lighter in color than the hair of other family members; it is also fragile and easily broken. By puberty, the hair problems may worsen until all the hair on the scalp is lost (total alopecia). The eyelashes, eyebrows, underarm (axillary) hair, and pubic hair are also sparse or absent.

Abnormal growth of fingernails and toenails (nail dystrophy) is also characteristic of Clouston syndrome. The nails may appear white in the first years of life. They grow slowly and gradually become thick and misshapen. In some people with Clouston syndrome, nail dystrophy is the most noticeable feature of the disorder.

Many people with Clouston syndrome have thick skin on the palms of the hands and soles of the feet (palmoplantar hyperkeratosis); areas of the skin, especially over the joints, that are darker in color than the surrounding skin (hyperpigmentation); and widened and rounded tips of the fingers (clubbing).

The prevalence of Clouston syndrome is unknown. Cases have been reported in many populations; the disorder is especially common among people of French-Canadian descent.

Clouston syndrome is caused by mutations in the GJB6 gene. This gene provides instructions for making a protein called gap junction beta 6, more commonly known as connexin 30. Connexin 30 is a member of the connexin protein family. Connexin proteins form channels called gap junctions, which permit the transport of nutrients, charged atoms (ions), and signaling molecules between neighboring cells. The size of the gap junction and the types of particles that move through it are determined by the particular connexin proteins that make up the channel. Gap junctions made with connexin 30 transport potassium ions and certain small molecules.

Connexin 30 is found in several different tissues throughout the body, including the skin (especially on the palms of the hands and soles of the feet), hair follicles, and nail beds, and plays a role in the growth and development of these tissues.

GJB6 gene mutations that cause Clouston syndrome change single protein building blocks (amino acids) in the connexin 30 protein. Although the effects of these mutations are not fully understood, they lead to abnormalities in the growth, division, and maturation of cells in the hair follicles, nails, and skin.

Genetic Testing Information

• Genetic Testing Registry: Hidrotic ectodermal dysplasia syndrome

Genetic and Rare Diseases Information Center

• Hidrotic ectodermal dysplasia

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Catalog of Genes and Diseases from OMIM

• CLOUSTON SYNDROME

Scientific Articles on PubMed

• PubMed

• Baris HN, Zlotogorski A, Peretz-Amit G, Doviner V, Shohat M, Reznik-Wolf H, Pras E. A novel GJB6 missense mutation in hidrotic ectodermal dysplasia 2 (Clouston syndrome) broadens its genotypic basis. Br J Dermatol. 2008 Dec;159(6):1373-6. doi: 10.1111/j.1365-2133.2008.08796.x. Epub 2008 Aug 19. No abstract available. Citation on PubMed
• Essenfelder GM, Bruzzone R, Lamartine J, Charollais A, Blanchet-Bardon C, Barbe MT, Meda P, Waksman G. Connexin30 mutations responsible for hidrotic ectodermal dysplasia cause abnormal hemichannel activity. Hum Mol Genet. 2004 Aug 15;13(16):1703-14. doi: 10.1093/hmg/ddh191. Epub 2004 Jun 22. Citation on PubMed
• Fraser FC, Der Kaloustian VM. A man, a syndrome, a gene: Clouston's hidrotic ectodermal dysplasia (HED). Am J Med Genet. 2001 Apr 22;100(2):164-8. doi: 10.1002/1096-8628(20010422)100:23.0.co;2-w. Citation on PubMed
• Fujimoto A, Kurban M, Nakamura M, Farooq M, Fujikawa H, Kibbi AG, Ito M, Dahdah M, Matta M, Diab H, Shimomura Y. GJB6, of which mutations underlie Clouston syndrome, is a potential direct target gene of p63. J Dermatol Sci. 2013 Feb;69(2):159-66. doi: 10.1016/j.jdermsci.2012.11.005. Epub 2012 Nov 16. Citation on PubMed
• Kibar Z, Der Kaloustian VM, Brais B, Hani V, Fraser FC, Rouleau GA. The gene responsible for Clouston hidrotic ectodermal dysplasia maps to the pericentromeric region of chromosome 13q. Hum Mol Genet. 1996 Apr;5(4):543-7. doi: 10.1093/hmg/5.4.543. Citation on PubMed
• Kibar Z, Dube MP, Powell J, McCuaig C, Hayflick SJ, Zonana J, Hovnanian A, Radhakrishna U, Antonarakis SE, Benohanian A, Sheeran AD, Stephan ML, Gosselin R, Kelsell DP, Christianson AL, Fraser FC, Der Kaloustian VM, Rouleau GA. Clouston hidrotic ectodermal dysplasia (HED): genetic homogeneity, presence of a founder effect in the French Canadian population and fine genetic mapping. Eur J Hum Genet. 2000 May;8(5):372-80. doi: 10.1038/sj.ejhg.5200471. Citation on PubMed
• Lamartine J, Munhoz Essenfelder G, Kibar Z, Lanneluc I, Callouet E, Laoudj D, Lemaitre G, Hand C, Hayflick SJ, Zonana J, Antonarakis S, Radhakrishna U, Kelsell DP, Christianson AL, Pitaval A, Der Kaloustian V, Fraser C, Blanchet-Bardon C, Rouleau GA, Waksman G. Mutations in GJB6 cause hidrotic ectodermal dysplasia. Nat Genet. 2000 Oct;26(2):142-4. doi: 10.1038/79851. No abstract available. Citation on PubMed
• Mellerio J, Greenblatt D. Hidrotic Ectodermal Dysplasia 2. 2005 Apr 25 [updated 2025 Apr 3]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from http://www.ncbi.nlm.nih.gov/books/NBK1200/ Citation on PubMed
• Smith FJ, Morley SM, McLean WH. A novel connexin 30 mutation in Clouston syndrome. J Invest Dermatol. 2002 Mar;118(3):530-2. doi: 10.1046/j.0022-202x.2001.01689.x. Citation on PubMed
• Zhang XJ, Chen JJ, Yang S, Cui Y, Xiong XY, He PP, Dong PL, Xu SJ, Li YB, Zhou Q, Wang Y, Huang W. A mutation in the connexin 30 gene in Chinese Han patients with hidrotic ectodermal dysplasia. J Dermatol Sci. 2003 Jun;32(1):11-7. doi: 10.1016/s0923-1811(03)00033-1. Citation on PubMed