Tetrasomy 18p Treatment and Surveillance

These recommendations are inclusive of the entire population of people with Tetrasomy 18p. It should be noted that there is a great deal of variation among individuals with Tetrasomy 18p. Not all complications or concerns will be listed in this document. However, the recommendations contained here should be used as a baseline for monitoring and the health of individuals with Tetrasomy 18p

The goal of this diagram is to illustrate the chromosome conformation that is Tetrasomy 18p. The diagram includes two images of a normal copy of chromosome 18 as well as a third extra chromosome composed of two chromosome 18 short or p arms joined together at their centromeres in an invered arrangement. Next to this diagram is a text box that says: Tetrasomy 18p. This condition is caused by an extra chromosome composed of 2 chromosome 18 p arms (i.e. an isochromosome). This results in a total of 4 copies of each of the genes on 18p. the p arm of chromosome 18 has 66 genes. Little is known about how the presence of four copies of these genes directly relates to the clinical features associated with Tetrasomy 18p. Therefore, we base our recommendations on descriptive studies of individuals with this condition.

Potential conditions in a neonate

  • Structural
      • Palate abnormality – 81%
      • Heart abnormalities -47% by Echo/ECG
      • Congenital orthopedic abnormalities-45%
      • Hernias-12%
      • Myelomeningocele-7%
  • Functional
      • Feeding problems – 83%
      • Respiratory distress – 31%
  • Biochemical
      • Jaundice – 57%

Initial evaluations after diagnosis

  • Ophthalmology
      • Strabismus –  75%
      • Refractive errors –  71%
  • Audiology / Otolaryngology
      • Hearing loss – 32%
      • Recurrent otitis media –  57%
  • Genitourinary
      • Cryptorchidism –  63%
      • Hypospadias – 7%
      • Urinary tract anomalies – 28%

Immediate Referrals to:

  • Appropriate sub-specialist as indicated by initial evaluations
  • Genetics follow-up if not previous to diagnosis
  • Early intervention/developmental services
  • The Chromosome 18 Registry & Research Society
  • The Chromosome 18 Clinical Research Center

Closely monitor and manage:

  • Failure to thrive/growth failure
      • Underweight (< 3rd percentile)
  • Endocrinology
      • Short stature (< 25th percentile)
      • Growth hormone deficiency
  • Otorhinolaryngology
      • Recurrent otitis media
      • Hearing loss
  • Gastrointestinal
      • Constipation
      • GE reflux
      • Hernias
      • Eosinophilic esophagitis
  • Immunology/Rheumatology
      • Atopic disorders
      • IgA deficiency
      • Eosinphiilic esophagitis
  • Orthopedics
      • Congenital hip dysplasia
      • Foot abnormalities
      • Decreased bone mineral density
  • Development
      • Milestones
      • School performance
      • Psychometric data
  • Dental
  • Neurology
      • Seizure
      • Hypotonia
  • Behavioral/mood changes

Annual Screenings

  • Vision
  • Hearing

Current Adult Status

Age and Cause of Death

Updated 2020

There is additional information on each of the areas mentioned above within the downloadable PDF document.

Updated 2020