Pallister Killian syndrome

Last revised by Yuranga Weerakkody on 23 Jan 2023

Pallister-Killian syndrome (PKS) is an extremely rare chromosomal anomaly.

It may be more prevalent in births from women of advanced age 4.

Phenotypic expression can significantly vary from multiple anomalies resulting in perinatal death to the more characteristic situation of:

Other anomalies include:

It is a polymalformative complex with tetrasomy of isochromosome 12p although many cases are mosaic.

The majority of cases are thought to be sporadic but in some cases, the degree of mosaicism in the chorion villus sample is much more lower than that in the fetal tissues subsequently examined. Confined placental mosaicism is a well-recognized phenomenon in a number of chromosomal abnormalities and is said to contribute to their intra-uterine survival.

Tetrasomy 12p is not always diagnosed, because the tissues are differently affected. Although it is present in a high percentage of fibroblasts, it is practically absent from the blood.

The mosaic forms make diagnosis difficult as there is a wide variety of potential radiographic features.

May show a combination of some of the above clinical features. There may be polyhydramnios as an ancillary sonographic feature 2.

Some of the clinical features can overlap with the Fryns syndrome 1.

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