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

Björnstad syndrome

Reviewed March 2014

What is Björnstad syndrome?

Björnstad syndrome is a rare disorder characterized by abnormal hair and hearing problems. Affected individuals have a condition known as pili torti, which means "twisted hair," so named because the strands appear twisted when viewed under a microscope. The hair is brittle and breaks easily, leading to short hair that grows slowly. In Björnstad syndrome, pili torti usually affects only the hair on the head; eyebrows, eyelashes, and hair on other parts of the body are normal. The proportion of hairs affected and the severity of brittleness and breakage can vary. This hair abnormality commonly begins before the age of 2. It may become milder with age, particularly after puberty.

People with Björnstad syndrome also have hearing problems that become evident in early childhood. The hearing loss, which is caused by changes in the inner ear (sensorineural deafness), can range from mild to severe. Mildly affected individuals may be unable to hear sounds at certain frequencies, while severely affected individuals may not be able to hear at all.

How common is Björnstad syndrome?

Björnstad syndrome is a rare condition, although its prevalence is unknown. It has been found in populations worldwide.

What genes are related to Björnstad syndrome?

Björnstad syndrome is caused by mutations in the BCS1L gene. The protein produced from this gene is found in cell structures called mitochondria, which convert the energy from food into a form that cells can use. In mitochondria, the BCS1L protein plays a role in oxidative phosphorylation, which is a multistep process through which cells derive much of their energy. The BCS1L protein is critical for the formation of a group of proteins known as complex III, which is one of several protein complexes involved in this process. As a byproduct of its action in oxidative phosphorylation, complex III produces reactive oxygen species, which are harmful molecules that can damage DNA and tissues.

BCS1L gene mutations involved in Björnstad syndrome alter the BCS1L protein and impair its ability to aid in complex III formation. The resulting decrease in complex III activity reduces oxidative phosphorylation. For unknown reasons, overall production of reactive oxygen species is increased, although production by complex III is reduced. Researchers believe that tissues in the inner ears and hair follicles are particularly sensitive to reactive oxygen species and are damaged by the abnormal amount of these molecules, leading to the characteristic features of Björnstad syndrome.

Related Gene(s)

Changes in this gene are associated with Björnstad syndrome.

  • BCS1L

How do people inherit Björnstad syndrome?

Björnstad syndrome 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 Björnstad syndrome?

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

  • Centers for Disease Control and Prevention: Hearing Loss in Children: Screening and Diagnosis (
  • Genetic Testing Registry: Pili torti-deafness syndrome (

You might also find information on the diagnosis or management of Björnstad 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 Björnstad syndrome?

You may find the following resources about Björnstad 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 Björnstad syndrome?

  • Bjornstad syndrome
  • BJS
  • deafness and pili torti, Bjornstad type
  • pili torti and nerve deafness
  • pili torti-deafness syndrome
  • pili torti-sensorineural hearing loss
  • PTD

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 Björnstad syndrome?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding Björnstad syndrome?

autosomal ; autosomal recessive ; cell ; DNA ; gene ; inherited ; mitochondria ; oxidative phosphorylation ; oxygen ; phosphorylation ; prevalence ; protein ; puberty ; reactive oxygen species ; recessive ; sensorineural ; sensorineural hearing loss ; syndrome

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


  • Hinson JT, Fantin VR, Schönberger J, Breivik N, Siem G, McDonough B, Sharma P, Keogh I, Godinho R, Santos F, Esparza A, Nicolau Y, Selvaag E, Cohen BH, Hoppel CL, Tranebjaerg L, Eavey RD, Seidman JG, Seidman CE. Missense mutations in the BCS1L gene as a cause of the Björnstad syndrome. N Engl J Med. 2007 Feb 22;356(8):809-19. (
  • Loche F, Bayle-Lebey P, Carriere JP, Bonafe JL, Bazex J, Schwarze HP. Pili torti with congenital deafness (Bjornstad syndrome): a case report. Pediatr Dermatol. 1999 May-Jun;16(3):220-1. (
  • Richards KA, Mancini AJ. Three members of a family with pili torti and sensorineural hearing loss: the Bjornstad syndrome. J Am Acad Dermatol. 2002 Feb;46(2):301-3. (
  • Selvaag E. Pili torti and sensorineural hearing loss. A follow-up of Bjørnstad's original patients and a review of the literature. Eur J Dermatol. 2000 Mar;10(2):91-7. Review. (
  • Siddiqi S, Siddiq S, Mansoor A, Oostrik J, Ahmad N, Kazmi SA, Kremer H, Qamar R, Schraders M. Novel mutation in AAA domain of BCS1L causing Bjornstad syndrome. J Hum Genet. 2013 Dec;58(12):819-21. doi: 10.1038/jhg.2013.101. Epub 2013 Oct 31. (


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: March 2014
Published: February 8, 2016