Tetrasomy 18p: Sixty-Second Summary
(Aliases: isochromosome 18p)
Key points on genotype
- Nearly all individuals with Tetrasomy 18p have the same genotype.
- Definitive diagnosis requires:A chromosome microarray to determine the precise region of net copy number change.
- A karyotype to demonstrate that the copy number change is due to an isochromosome.
- Almost all are de novo events as opposed to inherited from a parent.
- There have been a few case reports of parents with mosaicism or with a chromosome rearrangement.
- Parents may consider chromosome analysis to better define risks for future pregnancies.
Key Points on phenotype
- Most individuals are not medically fragile.
- Developmental delay is very common.
- The average full scale IQ score is 48, though there is a wide range of ability.
- Behavioral concerns are common.
- Life expectancy is believed to be near normal.
- Congenital anomalies are possible. Specifically, individuals with Tetrasomy 18p have an increased likelihood of myelomeningocele, heart defects, hernias, palate abnormalities and orthopedic abnormalities.
Follow-up
- Affected individuals do not appear to be at increased risk for adverse reactions to drugs or standard medical treatments.
- Recommendations for specific evaluations and treatments are in the following sections.
Enrollment
- 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 may contact Annice Hill at hilla3@uthscsa.edu or call (210) 567-5321.
- Enrollment requires the diagnostic genetics report and any other informative medical records
Consultation
- Daniel Hale, MD, Medical Director of the Chromosome 18 Clinical Research Center can be reached through Annice Hill at hilla3@uthscsa.edu or call (210) 567-5321.
Updated 2020