What is Pallister-Killian Syndrome (PKS)

Pallister-Killian Syndrome (PKS) is a rare and complex genetic condition characterized by a chromosomal anomaly known as tetrasomy 12p. This anomaly occurs in a mosaic pattern, meaning not all cells in the body are affected, which contributes to the variability in symptoms and clinical manifestations. PKS is an aneuploidy, or an alteration in the number of chromosomes, involving the presence of an isochromosome 12p, a duplication of the short arm of chromosome 12.

The syndrome is characterized by multiple congenital anomalies, intellectual disability of varying degrees, and a range of clinical features that may include hypotonia, epilepsy, feeding difficulties, and craniofacial abnormalities. Although the estimated incidence is about 1 in 20,000–25,000 live births, PKS is believed to be widely underdiagnosed due to the complexity of its diagnosis.

Symptoms and Diagnosis

PKS presents a wide range of symptoms, which may include:

  • Neonatal hypotonia (reduced muscle tone at birth).
  • Delayed psychomotor development.
  • Brachycephalic skull and distinctive facial features (high forehead, short nose, hypertelorism).
  • Epilepsy and other neurological abnormalities.
  • Congenital heart defects, gastrointestinal anomalies, and respiratory issues.

The diagnosis is not straightforward, as genetic mosaicism makes it difficult to detect the anomaly in all cells. The most reliable diagnostic techniques include:

  • Array CGH (comparative genomic hybridization) on skin biopsy.
  • FISH (fluorescence in situ hybridization) on specific tissues.
  • Chorionic villus sampling or amniotic fluid testing during pregnancy, although results can often be falsely negative.
  • Buccal smear, a less invasive diagnostic technique compared to a skin biopsy, which can provide reliable results and serves as a first-level diagnostic option.

However, the clinical recognition of PKS’s characteristic phenotypic traits, such as facial dysmorphisms and other distinctive features, is often the crucial starting point for suspecting the syndrome and initiating the diagnostic process.

Research and Support

Although there is no definitive cure for PKS, scientific research is making significant progress. Supportive therapies, such as physical therapy, speech therapy, and personalized educational interventions, are essential to improve the quality of life for patients. PKS Italia APS actively works to promote research and raise awareness within the medical-scientific community and society about the syndrome.

FAQ About Pallister-Killian Syndrome

Does Pallister-Killian Syndrome (PKS) have other names?
Yes, PKS is also known as Tetrasomy 12p, Isochromosome 12p, or Killian-Teschler Syndrome.

What does it mean that PKS is a genetic condition?
PKS is caused by an alteration in the genetic material of cells, specifically a duplication of the short arm of chromosome 12. "Genetic" refers to the presence of the anomaly in the DNA, but it does not imply inheritance.

Is PKS an inherited condition?
No, PKS is not inherited. It is a "de novo" and "sporadic" condition, meaning it is not passed down from parents but occurs randomly.

What causes PKS?
The exact cause is unknown. However, it is clear that it is not related to hereditary factors, environmental influences, or harmful substances ingested by the mother.

Which chromosome is involved in PKS?
PKS involves chromosome 12, specifically the short arm (12p), which is duplicated, resulting in tetrasomy 12p.

Is PKS a pure tetrasomy?
No, PKS is a mosaic syndrome, which means that some cells have the chromosomal anomaly while others do not.

How many people are affected by PKS?
The estimated incidence is about 1 in 25,000 live births. As of 2025, approximately 500 cases are known worldwide, with over 50 in Italy. However, the actual number of cases is believed to be much higher.

Is there a cure for PKS?
Unfortunately, there is no definitive cure for PKS. However, personalized supportive therapies can help improve development and quality of life.

Is research being conducted on PKS?
Yes, several research teams, including those at the Children’s Hospital of Philadelphia and the Policlinico Sant’Orsola Malpighi in Bologna, are studying the syndrome to better understand its genetic mechanisms and develop potential future therapies.

Is PKS easy to diagnose?
No, diagnosing PKS is complex due to genetic mosaicism and the tissue-specific distribution of isochromosome 12p. Karyotype analysis on peripheral blood often yields false-negative results. A buccal smear, a less invasive diagnostic technique than a skin biopsy, can provide reliable results and is a valid first-level diagnostic option. However, the clinical recognition of PKS’s characteristic phenotypic traits, such as facial dysmorphisms and other distinctive features, is often the crucial starting point for suspecting the syndrome and initiating the diagnostic process.