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What is Ring 18: A Sixty-Second Summary

ICD-10 = Q99.9 or Q93.89

Key points on genotype

  • Molecular and cytogenetic evaluations are both necessary to make a Ring 18 diagnosis.
  • Every patient has unique deletions from BOTH ends of the chromosome; thus Ring 18 is not a single “syndrome.” (For guidance developing an individualized gene-based interpretation see subsequent pages.)
  • Some patients have deletions that do not include the deletion of any genes from one of the chromosome arms.
  • Therefore, the clinical implication information is separated into 18q (Distal 18q-) and 18p (18p-) in the following pages.
  • Some genotype-phenotype correlations have been established and are explored more in the following pages.
  • ~20% have duplications just proximal to the breakpoint of up to 30 Mb in size
  • Ring 18 occurs in 1 out of 300,000 live births

Key Points on phenotype

  • Multiple congenital anomalies are possible. Specific phenotypes are dependent on the specific genes deleted  –  see the section of this report on molecular implications.
  • Developmental delay is always present
  • Intellectual disability is common but not inevitable
  • Failure to thrive and growth hormone deficiency are common
  • The risk for autism spectrum is higher than average
  • Life expectancy is believed to be near normal except for individuals with very large duplications in addition to the deletions.


  • Affected individuals  are not at increased risk for adverse reactions to drugs or standard medical treatments
  • Treatment is primarily symptomatic
  • Recommendations for specific evaluations  and treatments are in the following sections


  • The Chromosome 18 Clinical Research Center is enrolling anyone with any chromosome 18 abnormality in our longitudinal study of all aspects of the conditions.
  • Parents need to contact Annice Hill at or call (210) 567-5321
  • We need the diagnostic genetics report and any other informative medical records
  • Then we will schedule a blood draw and shipment


  • Daniel Hale, MD, Medical Director of the Chromosome 18 Clinical Research Center can be reached through Annice Hill at or call (210) 567-5321.

Updated 2020