Monoamine oxidase A deficiency

Monoamine oxidase A (MAO-A) deficiency, also known as Brunner syndrome, is a rare X-linked genetic disorder caused by mutations in the MAOA gene located on chromosome Xp11.3. Monoamine oxidase A is an enzyme responsible for the breakdown of neurotransmitters including serotonin, norepinephrine, and dopamine. When this enzyme is deficient or absent, these monoamines accumulate in the brain, leading to significant behavioral and neurological disturbances. The condition primarily affects the central nervous system and is characterized by borderline intellectual disability (mild cognitive impairment), impulsive aggressive behavior, and behavioral disturbances including violent outbursts, arson, attempted rape, and other antisocial behaviors. Affected males may also exhibit sleep disturbances, night terrors, and stereotyped hand movements such as hand wringing or hand flushing. Biochemically, affected individuals show elevated urinary levels of serotonin, norepinephrine, and their metabolites, along with abnormal monoamine metabolism. Because the condition is X-linked recessive, it predominantly affects males, while females are typically carriers who may show milder or no symptoms. The disorder was first described in a large Dutch kindred by Brunner and colleagues in 1993. There is currently no specific cure for MAO-A deficiency. Management is primarily supportive and symptomatic, focusing on behavioral interventions and pharmacological approaches to manage aggression and impulsivity. Dietary modifications to reduce tyramine intake may be considered given the impaired monoamine metabolism. Genetic counseling is recommended for affected families.

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