Pallister-Killian Syndrome (PKS) is a rare chromosomal disorder in which there are 2 extra copies of the short (p) arm of chromosome 12. It is a mosaic condition, meaning that not all cells in a particular tissue have these extra chromosomes and a percentage of cells are normal. This is called “mosaic tetrasomy 12p”. The severity of the effects of this extra condition varies enormously. The number of affected cells does not correlate to the severity in each individual.
It is estimated that there are some 500 – 700 cases of PKS diagnosed worldwide. In Australia there are around 15-20 known cases. Most of these cases have been diagnosed in the last 5 years with an increasing diagnosis rate. Being so rare, the condition is often undiagnosed during pregnancy. Sometimes it is identified through an anomaly picked up during ultrasound and further investigation is undertaken. More often PKS is identified at birth or soon after due to characteristic appearance or other complications.
Diagnosis is made by obtaining cells from:
- Skin Biopsy
- Buccal Swabs (cheek swab)
- Tissue biopsy
- Amniotic fluid cells
- Bone Marrow
Scientific advances are enabling increasingly reliable diagnosis of this condition.
Features of PKS include:
- Global developmental delay
- Mild to profound intellectual impairment
- Marked hypotonia (floppiness)
- Hearing and/or vision impairment
- Difficulty in feeding and oesophageal reflux
- Congenital heart defects
- Prominent high forehead
- Coarse facial features as child gets older
- Broad nasal bridge
- Streaks or patches of lighter or darker skin
- Sparse hair or bald patches
- High arched or cleft palate
- Shorter arms and legs, disproportionate to the body
- Extra nipples
Along with the physical aspects of the condition, constipation and respiratory infections are also common.
Many people diagnosed with PKS are not unable to walk or talk. Many do not communicate at all. These individuals are dependent on others for every thing in life often including feeding, recreation, physical activity, socialisation, education and personal care.