Pallister-Killian syndrome (PKS)

What is Pallister-Killian syndrome (PKS)?

Pallister-Killian syndrome is a very rare genetic condition with just 150 recorded cases to date. Although this figure may actually be higher as individuals with mild symptoms may go undiagnosed.

This rare disease is a multi-system disorder. Its defining features include low muscle tone (hypotonia) in infancy and early childhood, intellectual disability, unique facial features and other features which are usually present at birth.

What gene changes cause Pallister-Killian syndrome (PKS)?

The syndrome is caused by the presence of an extra abnormal chromosome, known as isochromosome 12p, meaning a cell may have up to four copies of the small arm of chromosome 12.

The syndrome is not inherited and occurs due to mutations during reproductive cell production in the parents which leads to mosaicism, some cells may have the abnormality, some may not. Most occur due to mutations in the mother’s cells.

Mosaic inheritance occurs very early in the development of a fetus. Essentially it is an error in cell division. The human body is made up of 46 chromosomes, in 23 pairs. Mosaicism occurs when an individual has cells in their body with more or less chromosomes than the usual 46. This can trigger issues that affect different systems and parts of the body.

What are the main symptoms of Pallister-Killian syndrome (PKS)?

Facial and physical characteristics include sparse hair, a high forehead, broad nasal bridge, widely spaced eyes, low set ears, rounded cheeks, a cleft or high arched palate.

Extra fingers or toes, a large big toe and short arms and legs also characterize the syndrome.

Infants with the syndrome are often born with birth defects, as well as unusual skin coloring in patches of the skin. 30% of individuals will also suffer from serious mobility issues and be unable to walk unassisted.

One of the most serious syndromes associated with the syndrome is extremely low muscle tone, as this can cause breathing and feeding difficulties in infants. 40% of individuals are born with a congenital diaphragm hernia that can cause serious medical complications concerning the internal organs.

Individuals with the syndrome may also experience hearing and vision loss and generally present with limited or zero speech.

How does someone get tested for Pallister-Killian syndrome (PKS)?

The initial testing for Pallister-Killian syndrome can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow. 

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.   

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Parents of Lillie

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