Pallister-Killian-Syndrom
Pallister-Killian syndrome (PKS) is an extremely rare chromosomal anomaly.
Epidemiology
It may be more prevalent in births from women of advanced age .
Clinical presentation
Phenotypic expression can significantly vary from multiple anomalies resulting in perinatal death to the more characteristic situation of:
- profound intellectual disability
- coarse facial appearance
- pigmentary anomalies
- localized alopecia in the temporofrontal area
- hypertelorism
- long philtrum
- acral hypoplasia
Other anomalies include:
- anteverted nostrils
- small and apparently low-set ears
- simian crease
- clinodactyly
- congenital heart disease: may be seen in up to 25% of cases
- congenital diaphragmatic hernia: may be seen in up to 50% of cases
- rhizomelic limb shortening
Pathology
It is a polymalformative complex with tetrasomy of isochromosome 12p although many cases are mosaic.
Genetics
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.
Radiographic features
The mosiac forms make diagnosis difficult as there is a wide variety of potential radiographic features.
Antenatal ultrasound
May show a combination of some of the above clinical features. There may be polyhydramnios as an ancillary sonographic feature .
Differential diagnosis
Some of the clinical features can overlap with the Fryns syndrome .
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