Medicine:Brunner syndrome

From HandWiki
Short description: X-linked recessive disorder characterised by impulsive behaviour
Brunner syndrome
Other namesMonoamine oxidase A deficiency
X-linked recessive (carrier mother).svg
This condition is inherited in an X-linked recessive manner.

Brunner syndrome is a rare genetic disorder associated with a mutation in the MAOA gene. It is characterized by lower than average IQ (typically about 85), problematic impulsive behavior (such as pyromania, hypersexuality and violence), sleep disorders and mood swings.[1][2] It was identified in fourteen males from one family in 1993.[1][3] It has since been discovered in additional families.[4]

Signs and symptoms

The following signs and symptoms occur in people with monoamine oxidase A deficiency, which causes Brunner syndrome:[5]

  • lack of impulse control
  • aggressive or violent outbursts
  • ASD or ADHD-like behavioral features
    • obsessive behaviors
    • difficulties forming friendships
    • problems focusing attention
  • sleep problems
    • trouble falling asleep
    • night terrors
  • skin flushing
  • sweating
  • headaches
  • diarrhea


Brunner syndrome is caused by a monoamine oxidase A (MAOA) deficiency, which leads to an excess of monoamines in the brain, such as serotonin, dopamine, and norepinephrine (noradrenaline). In both mice and humans, a mutation was located on the eighth exon of the MAO-A gene, which created a dysfunctional MAO-A gene.[6][7] The regular function of MAO-A, breaking down monoamines, is disrupted, and monoamines build up within the brain. Mice that lacked a functional MAO-A gene displayed higher levels of aggression, in comparison to mice with a functional MAO-A gene.[7]


Upon suspicion of Brunner syndrome and after having eliminated other potential suspects via means of differential diagnosis, Brunner syndrome is diagnosed by genetic testing for specific mutations of the MAOA gene. Since the syndrome is so rare, it is usually only suspected and tested for if there are other diagnosed instances of the syndrome in one's direct family.


Progesterone & Rauwolfia serpentina (containing Reserpine) are a possible treatment as they both increase MAO-A activity.


Brunner Syndrome was described in 1993 by H.G. Brunner and his colleagues upon the discovery of a particular genetic defect in male members of a large Dutch family.[6] Brunner found that all of the male family members with this defect reacted aggressively when angry, fearful, or frustrated. The defect discovered was later found to be a mutation in the gene that codes for monoamine oxidase A (MAOA gene).[6] Brunner said that an "MAO-A deficiency is associated with a recognizable behavioural phenotype that included disturbed regulation of impulsive aggression".[6]

A letter published by Hebebrand and Klug (1995)[8] criticized Brunner's findings for not using strict DSM criteria.

Society and culture

Brunner's findings have been used to argue that genetics, rather than decision-making processes, can cause criminal activity.[9] Evidence supporting the genetic defense stems from both Brunner's findings and a series of studies on mice.[10] To prove the correlation between MAO-A deficiency and aggression in courts, it is often contended that individuals cannot be held accountable for their genes, and as a result, should not be held responsible for their dispositions and resulting actions.[9][10]


  1. 1.0 1.1 Hunter P (September 2010). "The psycho gene". EMBO Rep. 11 (9): 667–9. doi:10.1038/embor.2010.122. PMID 20805840. 
  2. Online Mendelian Inheritance in Man (OMIM) 300615
  3. Brunner HG; Nelen MR; van Zandvoort P; Abeling NGGM; van Gennip AH; Wolters EC; Kuiper MA; Ropers HH et al. (June 1993). "X-linked borderline mental retardation with prominent behavioral disturbance: phenotype, genetic localization, and evidence for disturbed monoamine metabolism". Am. J. Hum. Genet. 52 (6): 1032–9. PMID 8503438. 
  4. "XLID-causing mutations and associated genes challenged in light of data from large-scale human exome sequencing". Am. J. Hum. Genet. 93 (2): 368–83. August 2013. doi:10.1016/j.ajhg.2013.06.013. PMID 23871722. 
  5. "Monoamine oxidase A deficiency". 
  6. 6.0 6.1 6.2 6.3 "Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase A". Science 262 (5133): 578–80. October 1993. doi:10.1126/science.8211186. PMID 8211186. Bibcode1993Sci...262..578B. 
  7. 7.0 7.1 Scott, AL; Bortolato, M; Chen, K; Shih, JC (2008-05-07). "Novel monoamine oxidase A knock out mice with human-like spontaneous mutation.". NeuroReport 19 (7): 739–43. doi:10.1097/WNR.0b013e3282fd6e88. PMID 18418249. 
  8. "Specification of the phenotype required for men with monoamine oxidase type A deficiency". Hum. Genet. 96 (3): 372–6. September 1995. doi:10.1007/BF00210430. PMID 7649563. 
  9. 9.0 9.1 "The genetic defence: the impact of genetics on the concept of criminal responsibility". Health Law J 12: 35–70. 2004. PMID 16539076. 
  10. 10.0 10.1 "Behavioral genetics: the science of antisocial behavior". Law Contemp Probl 69 (1–2): 7–46. 2006. PMID 18176636. 

External links

External resources