MAOA/B deletion syndrome in male siblings with severe developmental delay and sudden loss of muscle tonus

Brain Dev. 2014 Jan;36(1):64-9. doi: 10.1016/j.braindev.2013.01.004. Epub 2013 Feb 13.


Deletion of the monoamine oxidase (MAO)-A and MAO-B was detected in two male siblings and in their mother. The approximately 800-kb deletion, extending from about 43.0MB to 43.8MB, was detected by array comparative genomic hybridization analysis. The MAOA and MAOB genes were included in the deletion, but the adjacent Norrie disease gene, NDP, was not deleted. The boys had short stature, hypotonia, severe developmental delays, episodes of sudden loss of muscle tone, exiting behavior, lip-smacking and autistic features. The serotonin levels in their cerebrospinal fluid were extremely elevated. Another set of siblings with this deletion was reported previously. We propose recognition of MAOA/B deletion syndrome as a distinct disorder.

Keywords: Hypotonia; Monoamine oxidase (MAO); Serotonin; Severe developmental delay; Short stature; Sudden loss of muscle tone.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catecholamines / blood
  • Catecholamines / cerebrospinal fluid
  • Child, Preschool
  • Comparative Genomic Hybridization
  • Developmental Disabilities / blood
  • Developmental Disabilities / cerebrospinal fluid
  • Developmental Disabilities / complications*
  • Developmental Disabilities / genetics*
  • Humans
  • Male
  • Monoamine Oxidase / deficiency*
  • Muscle Hypotonia / blood
  • Muscle Hypotonia / cerebrospinal fluid
  • Muscle Hypotonia / etiology*
  • Muscle Hypotonia / genetics
  • Serotonin / blood
  • Serotonin / cerebrospinal fluid
  • Siblings


  • Catecholamines
  • Serotonin
  • Monoamine Oxidase
  • monoamine oxidase A, human