Hair-pulling disorder caused by faulty gene in some families 27/9/06. By Duke University Medical Center Researchers have found gene mutations that cause trichotillomania, a psychiatric disorder that triggers people to compulsively pull their hair.

Trichotillomania, a psychiatric disorder that triggers people to compulsively pull their hair, affects between 3 per cent and 5 per cent of the population and is considered an impulse control disorder. Patients with trichotillomania have noticeable hair loss or patches of baldness, but they often mask their habit. As a result, the disorder often goes undiagnosed and untreated, said researchers.

The relatively unknown disorder is often accompanied by other psychiatric conditions, such as anxiety, depression, obsessive compulsive disorder or Tourette syndrome, which are better known than the hair-pulling behaviour.

Scientists at Duke University Medical Center found two mutations in a gene called SLITKR1 that were implicated in trichotillomania patients. The mutations account for only a small percentage of trichotillomania cases, said the scientists.

However, their findings are significant because they validate a biological basis for mental illnesses. Such illnesses have long been blamed on a person's upbringing or life experiences, said lead study investigator Stephan Züchner at the Duke Center for Human Genetics.

"Society still holds negative perceptions about psychiatric conditions such as trichotillomania. But, if we can show they have a genetic origin, we can improve diagnosis, develop new therapies and reduce the stereotypes associated with mental illness," Züchner said.

Currently, there is no specific treatment for trichotillomania, although it is sometimes successfully managed with drugs used for depression and anxiety disorders.

The Duke scientists studied 44 families with one or more members who had trichotillomania. The researchers studied SLITRK1 because it was linked last year to the related impulse-control disorder Tourette syndrome, which causes repetitive behaviours such as blinking, throat-clearing or shouting obscenities. The parent of one patient with Tourette syndrome carried the SLITRK1 mutation but displayed only symptoms of trichotillomania, not Tourette syndrome.

The Duke team found two mutations in the SLITRK1 gene among some individuals with trichotillomania but not in their unaffected family members. Mutations are changes in the structure of a gene that alter how the gene behaves. The researchers estimate that the SLITRK1 mutations account for 5 per cent of trichotillomania cases.

The SLITRK1 gene is involved in forming connections among neurons, or brain cells. The researchers hypothesise that the two mutations in SLITRK1 cause neurons to develop faulty connections and that this faulty 'wiring' produces the urge to pull one's hair.

While SLITRK1 is the first gene linked with trichotillomania, numerous other genes are likely to contribute to this disorder and other psychiatric conditions, said senior study investigator Allison Ashley-Koch.

"The SLITRK1 gene could be among many other genes that are likely to interact with each other and environmental factors to trigger trichotillomania and other psychiatric conditions," Ashley-Koch said. "Such discoveries could open the door for genetic testing, which is completely unheard of in the field of psychiatry."

Compared with neurological diseases, the identification of genes that underlie psychiatric disorders have only just begun, she said. Few other examples exist where a specific gene is known to trigger a psychiatric condition, although it is generally accepted that genetic factors play an important role.

Adapted from a news release by Duke University Medical Center .

Above image courtesy of the Wellcome Trust Medical Photographic Library .

References

Zuchner S, et al. SLITRK1 mutations in trichotillomania. Mol Psychiatry 2006;11(10):887.