The Pallister-Killian Syndrome ( PKS ) is a rare, mosaic, polymalformative, genetic disease.

Does it have other names? 

It 's also called Tetrasomy 12p mosaicism, or Pallister Mosaic Syndrome , or Isochromosome 12p, or Teschler-Killian Syndrome .

What does"genetic disease" mean? 

It 'a disease due to a genetic alteration of the cells, in this case due to an abnormality in chromosome's number.

Is it hereditary?

It is not hereditary. Its occurrence is sporadic and completely random .

What is the cause?

As of today, the cause is not known. However, it is known that it is not hereditary, environmental related or due to a harmful substance ingested.

What does " mosaic " means?

The PKS is a mosaic syndrome. Genetic mosaic, or mosaicism, means that an individual own two or more different genetic lines expressed simultaneously. In a nutshell , a part of the cells presents a "normal" chromosome and another part presents an alterated chromosome. 

Which chromosome is involved?

The anomaly is in the chromosome 12. The chromosome 12 is typically composed of a short arm ( 12p ) and a long arm ( 12q ) . In the PKS the altered chromosome has a duplication of the segment of the short arm ( isochromosome 12p ) . The result is that the altered cells have 4 copies of the short arm ( tetrasomy 12p ) instead of the normal two .

tetrasomia 12p

How many people are affected?

 The incidence is not certain and is estimated to be 1/25.000 . There are about 300 known cases in the world, about 30 in Italy . Since there is no national registry or global data , however, this number may be inaccurate. Pyisicians estimate taht, only in the United States, there may be more than two thousand cases.

Is there a cure? 

To this day, there is no cure. There are supportive therapies, such as physiotherapy and speech therapy, which can help and support the development of certain skills .

Are there research?

The team of doctors at the Children's Hospital of Philadelphia, USA, conducted by Dr. Ian Krantz ,  is performing important studies on the PKS, to identify the "responsible gene"  and then begin to develop a gene therapy. A therapy which can correct the excessive workload due to the presence of four copies of that gene.

Is it easy to be diagnosed?

The diagnosis is not easy because of the distribution of mosaic tissue-specific isochromosome 12p.

Is it possible to have a pre-birth diagnosis? 

The diagnosis during pregnancy is only possible in some cases. Sometimes, when malformations in the fetus are very striking, the morphological ultrasound may point out the need of further in-depth investigations of genetic which may , in some cases, identify the tetrasomy 12p . A 3D morphological ultrasound can sometimes highlight the craniofacial features ( facies ), very typical of infants with PKS. Other times invasive cytogenetics tests can detect the chromosomal anomaly.

The chorionic villus sampling and amniocentesis give a definite result?

Sometimes the PKS can be detected by chorionic villus sampling or amniotic fluid. However, they can often result in a false negative, becasue the colected cells do not exhibit the anomaly.

Can it can be diagnosed by a blood test?

The blood cells regenerate very quickly and the new ones do not show the anomaly. For this reason, an examination of the lymphocytes in the peripheral blood  often leads to a false negative result.

How can it be cerainly diagnosed?

The most effective diagnostic methods to detect the PKS are skin biopsy and buccal smear .

What are the characteristics of children with PKS?

These are some features present in most individuals with PKS. However, it is very important to emphasize the fact that there is a very wide variability, both between the characteristics which occur in an affected individual , and  in the severity of their manifestation.



  • High hypotonia at birth, often persistent
  • Psycho-motor delay, from moderate to very deep
  • Coarse facies with typical features ( flat profile , high forehead , prominent fronto-temporal alopecia, rarefied eyebrows and eyelashes, shallow supraorbital ridges, upward slanting palpebral fissures, hypertelorism, strabismus, epicantale folds, flat nasal bridge and enlarged, short nose with nostrils facing up, long philtrum, large mouth with down-turned corners, thin upper lip, low-set ears)
  • Thinning hair at birth and temporal alopecia
  • Light or dark streaks on the skin
  • Extra nipples
  • Diaphragmatic hernia
  • Undescended testes
  • Bifid uvula
  • Anorectal malformations
  • Epilepsy
  • Hearing and Vision impairment




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