Brunner syndrome

Brunner syndrome is a rare genetic disorder associated with a lower than average IQ, typically around 85, along with problematic impulsive and often aggressive behavior. It is caused by a mutation in the MAOA gene, which normally produces the enzyme monoamine oxidase A; loss of this enzyme's activity allows monoamine neurotransmitters such as serotonin, dopamine, and norepinephrine to build up in the brain rather than being broken down normally. The condition is inherited in an X-linked recessive pattern and so affects males far more often than females. Reported features include a lack of impulse control with violent outbursts, autism spectrum or ADHD-like traits, sleep disturbances such as night terrors and insomnia, and additional symptoms including skin flushing, sweating, headaches, and diarrhea, with some individuals also showing pyromania or hypersexuality. The disorder was first identified in 1993 by the clinical geneticist H. G. Brunner and colleagues, who studied fourteen affected men across several generations of one Dutch family and described a pattern of disturbed regulation of impulsive aggression running through the family.