Brunner syndrome is a rare

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

associated with a

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...

in the MAOA gene. It is characterized by lower than average IQ (typically about 85), problematic impulsive behavior (such as

pyromania Pyromania is an impulse control disorder in which individuals repeatedly fail to resist impulses to deliberately start fires, to relieve some tension or for instant gratification. The term ''pyromania'' comes from the Greek word (''pyr'', 'fi ...

hypersexuality Hypersexuality is extremely frequent or suddenly increased libido. It is controversial whether it should be included as a clinical diagnosis used by mental healthcare professionals. Nymphomania and satyriasis were terms previously used for the c ...

and violence), sleep disorders and mood swings. It was identified in fourteen males from one family in 1993. It has since been discovered in additional families.

Signs and symptoms

Causes

Brunner syndrome is caused by a

monoamine oxidase A Monoamine oxidase A, also known as MAO-A, is an enzyme that in humans is encoded by the ''MAOA'' gene. This gene is one of two neighboring gene family members that encode mitochondrial enzymes which catalyze the oxidative deamination of amines, ...

(MAOA) deficiency, which leads to an excess of

monoamines Monoamine neurotransmitters are neurotransmitters and neuromodulators that contain one amino group connected to an aromatic ring by a two-carbon chain (such as -CH2-CH2-). Examples are dopamine, norepinephrine and serotonin. All monoamines ar ...

in the brain, such as serotonin, dopamine, and

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad' ...

(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. 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.

Diagnosis

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.

Treatment

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

History

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. 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). Brunner said that an "MAO-A deficiency is associated with a recognizable behavioural phenotype that included disturbed regulation of impulsive aggression". A letter published by Hebebrand and Klug (1995) 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. Evidence supporting the genetic defense stems from both Brunner's findings and a series of studies on mice. 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.

References

External links

{{Amino acid metabolic pathology Rare syndromes Genetic diseases and disorders Amino acid metabolism disorders