Pallister Mosaic Syndrome; Pallister-Killian Mosaic Syndrome; Killian Syndrome; Teschler-Nicola/Killian Syndrome; Tetrasomy 12p Syndrome; Tetrasomy 12p Mosaic Syndrome; Isochromosome 12p Syndrome

Pallister-Killian Syndrome (PKS) is a rare genetic disorder in which a person has four copies of the short arm of chromosome 12 (isochromosome 12p), instead of the normal two copies. The extra genetic material from isochromosome 12p disrupts the normal course of development, causing the characteristic features of this disorder.

Diagnostic testing: The diagnosis of PKS is made by physical examination and then confirmed by finding the presence of the extra genetic material of isochromosome 12p on a chromosome test.

Physical findings: Children with PKS have:

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  Extremely weak muscle tone (hypotonia);

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  Developmental delay/intellectual disability;

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  Distinctive facial features;

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  Sparse hair on the scalp;

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  Abnormally wide space between the eyes;

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  Extra skin folds over the corners of the eyes;

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  High arched or cleft palate;

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  Pale areas on the skin;

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  Hearing loss;

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  Vision impairment;

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  An extra nipple;

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  Genital abnormalities;

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  Heart defects; and

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  Skeletal abnormalities (i.e., extra fingers/toes, and unusually short arms and legs).

ICD-9: 759.89

Onset is congenital. Many infants with PKS die before they are born (that is, in utero) or soon after birth. Infants who survive birth have significant hypotonia, which can cause difficulty breathing and problems with feeding. Hypotonia also interferes with the normal development of motor skills, such as sitting, standing, and walking. About 30 percent of affected children are ultimately able to walk without assistance. Additional developmental delays result from intellectual disability, which is usually severe to profound. Speech is often limited or absent in children with this condition. About 40 percent of affected infants are born with a congenital diaphragmatic hernia, in which there is an abnormal opening in the diaphragm (the muscle that separates the abdomen from the chest cavity). This potentially serious birth defect allows the stomach and intestines to move into the chest, where they can crowd the developing heart and lungs. The physical manifestations of PKS progress with age. The prognosis for PKS is poor, although several people have been identified with mild intellectual disability and less obvious physical abnormalities.

Treatment is dependent on the medical condition of the individual and the affected organ defects. Affected school age children may benefit from early intervention programs and special education.

Suggested MER for Evaluation:

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  Clinical history and examination that describes the diagnostic features of the impairment; and

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  Laboratory tests showing results of genetic testing (chromosomal analysis).

REMARKS

Listing-level severity must be documented; evaluate under the most affected body systems.