Anorexia Nervosa, Susceptibility to, 1

Alternative Names

  • ANON1
  • AN
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WHO-ICD-10 version:2010

Mental and behavioural disorders

Behavioural syndromes associated with physiological disturbances and physical factors

OMIM Number

606788

Mode of Inheritance

Multifactorial

Gene Map Locus

11p13,13q14-q21

Description

Anorexia Nervosa (AN) is an eating disorder characterized by deliberate weight loss induced and sustained by the patient, and body image distortion, propelled by a phobia of gaining weight. Typical symptoms include voluntary weight loss by restricted dietary choice, excessive exercise, induced vomiting and purgation, and use of diet pills and diuretics, amenorrhea, blotchy or yellow skin, depression, low blood pressure, and loss of fatty tissue. AN is a complex condition that most likely results from psychological, neurobiological, and sociological factors, and is most commonly seen in adolescent girls and young women. However, adolescent boys and young men, children approaching puberty, and older women may also be affected.

Treatment of the condition initially involves immediate weight gain. This may be difficult, since most patients refuse to take food. Psychotherapy is an important component of the treatment strategy. Recent reports have pointed out that zinc supplementation of the diet plays a major role in managing the disease, probably due to an increase in effectiveness of neurotransmission in the amygdale. AN has a high mortality rate, with the most common causes of death being cardiac arrest, electrolyte imbalances, and suicide. Although experienced treatment programs have a good success rate in restoring normal weight, relapse is common.

Molecular Genetics

AN has been definitely shown to have a genetic component. This is brought forward in cases were both twins have been shown to be affected. In addition, females in a family with an eating disorder have been shown to be more susceptible to developing an eating disorder themselves. Genetic vulnerability to ED may involve factors relating to feeding and appetite, energy metabolism, development, personality and mood.

Mapping studies identified a locus on chromosome 1p, whish segregated with the disease condition in affected families. It is not clear what gene in this locus is responsible for the condition. However, researchers speculate that the hypothalamic-pituitary-adrenal axis may be involved. Affected patients have been shown to have abnormal neurotransmitter levels in the brain. Another candidate gene is the Brain-Derived Neurotrophic Factor (BDNF) on chromosome 11, which has been shown to induce appetite suppression and body weight reduction through a central mechanism that may involve the serotoninergic neurotransmitter system.

Epidemiology in the Arab World

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Other Reports

Oman

Al-Adawi et al. (2002) surveyed eating attitudes in Oman among adolescents and adults of both sexes. The results of data analysis revealed that the Omani teenage group were more susceptible and 4.9 times more likely to develop anorexic-like behavior then the non-Omani group, as 33% (35/106) of Omani students (29.4% of females and 36.4% of males showed disordered eating patterns) showed a propensity for anorexic-like behavior when compared to only 9.2% (8/87) of the other group (7.5% of males and 10.6% of females showed disordered eating patterns). 

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