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Pallister Killian syndrome

Tetrasomy 12p mosaicism, Pallister mosaic aneuploidy syndrome

Overview

Pallister–Killian syndrome ( tetrasomy 12p mosaicism, Pallister mosaic aneuploidy syndrome) is an extremely rare genetic disorder occurring in humans. Pallister-Killian occurs due to the presence of the anomalous extra isochromosome 12p, the short arm of the twelfth chromosome. This leads to the development of tetrasomy 12p. Because not all cells have the extra isochromosome, Pallister-Killian is a mosaic condition.

It was first described by Philip Pallister in 1977 and further researched by Maria Teschler-Nicola and Wolfgang Killian in 1981

Symptoms - Pallister Killian syndrome

Patients with Pallister-Killian Mosaic Syndrome typically have low muscle tone at birth, sparse scalp hair at birth, a high forehead, a coarse face, an abnormally wide space between the eyes, a broad nasal bridge, a highly arched palate, a fold of the skin over the inner corner of the eyes, and large ears with lobes that are thick and protrude outward. Other features frequently found in patients with this disorder may include: streaks of skin in which there is no color (hypopigmentation), extra nipples, seizures at birth, droopy upper eyelids, crossed eyes (strabismus), joints that will not move (contractures), and delays in perceiving, recognizing, judging, sensing, reasoning or imagining (cognitive delays). Congenital heart defects, hernia\'s of the diaphragm, a narrowing of the external auditory canal (stenosis) and an abnormal opening in the anus have also been associated with Pallister-Killian Mosaic Syndrome.

Causes - Pallister Killian syndrome

Pallister-Killian does not appear to be hereditary. Some research has suggested that the presence of the extra chromosome may be linked to premeiotic mitotic errors, both maternally and paternally. Several theories regarding the mechanism of this formation have been introduced.

Prevention - Pallister Killian syndrome

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Diagnosis - Pallister Killian syndrome

The isochromosome can be primarily detected in samples of skin fibroblasts, as well as in chorionic villus and amniotic fluid cell samples. Very rarely, it can also be detected in blood lymphocytes. It is also possible to detect the isochromosome in circulating lymphocytes, as well as other amniotic and placental samples. There is no strict limit as to where the isochromosome can be found. However, it is often unlikely that these samples will be tested when the blood karyotype is normal.

Using an ultrasound, Pallister-Killian may be diagnosed through observation of hypertelorism, broad neck, shorts limbs, abnormal hands or feet, diaphragmatic hernia, and hydramnios. Once born, a child may be diagnosed by observation of the syndrome's distinct facial features.

Prognosis - Pallister Killian syndrome

Many infants with PKS die before they are born (in utero) or soon after birth. Some affected individuals reaching their 20s have been reported. Many have severe to profound mental retardation and very few self-care skills. A few reports have described affected persons with milder intellectual impairment.

Treatment - Pallister Killian syndrome

There is no treatment or cure for PKS, or for the mental retardation and developmental delays associated with this syndrome. Persons with PKS are treated for the symptoms they display. Individuals with Pallister-Killian syndrome will often take medications for seizures; some may have surgeries due to birth defects involving the diaphragm, intestines, anus, kidneys, genitals, or heart. Physical therapy and occupational therapy may be helpful for development of muscle tone and reduction of joint fixation.

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