What is the history of Pallister-Killian Syndrome / Tetrasomy 12p?

Pallister-Killian Syndrome, also known as Tetrasomy 12p, is a rare genetic disorder characterized by the presence of extra genetic material on the short arm of chromosome 12. This condition was first described in 1977 by Dr. David W. Smith and his colleagues, who identified a distinct pattern of physical and developmental abnormalities in a group of individuals.

The cause of Pallister-Killian Syndrome is a chromosomal abnormality called mosaic tetrasomy 12p. Mosaic means that the extra genetic material is present in some cells of the body but not in others. In this case, the extra genetic material is a duplication of the short arm of chromosome 12, resulting in four copies instead of the usual two. This duplication can occur during early embryonic development and is not inherited from the parents.

The symptoms and severity of Pallister-Killian Syndrome can vary widely, even among affected individuals with the same genetic mutation. However, there are some common features that are often observed. These include:

• Distinctive facial features such as a high forehead, sparse hair, widely spaced eyes, and a flat nasal bridge.


• Intellectual disability and developmental delays, including delays in motor skills, speech, and language.


• Hypotonia, or low muscle tone, which can contribute to feeding difficulties and delays in achieving motor milestones.


• Seizures, which may be difficult to control with medication.


• Hearing and vision problems, including hearing loss and strabismus (crossed eyes).


• Abnormalities of the skeletal system, such as scoliosis (curvature of the spine) and joint contractures.


• Organ abnormalities, including heart defects, kidney abnormalities, and gastrointestinal issues.

Diagnosis of Pallister-Killian Syndrome is typically made through genetic testing to identify the presence of the extra genetic material on chromosome 12. However, because the duplication is mosaic, it may not be detected in all cells, making diagnosis challenging. In some cases, a skin biopsy may be necessary to analyze the genetic material in a specific tissue.

There is currently no cure for Pallister-Killian Syndrome, so treatment focuses on managing the symptoms and providing supportive care. Early intervention services, including physical therapy, occupational therapy, and speech therapy, can help individuals with developmental delays reach their full potential. Seizures may be treated with anticonvulsant medications, and other medical issues are addressed as they arise.

Prognosis for individuals with Pallister-Killian Syndrome varies depending on the severity of symptoms and associated health issues. Some individuals may have a relatively mild presentation and live into adulthood with appropriate medical care and support. However, others may have more significant medical complications that can impact lifespan.

Research into Pallister-Killian Syndrome is ongoing, with a focus on understanding the underlying genetic mechanisms and potential targeted therapies. Genetic counseling is recommended for families affected by this condition to provide information about the risk of recurrence and available testing options.