Handbook of Genetic Counseling/Pallister-Killian Syndrome

Pallister-Killian Syndrome

Genetic Etiology

• Tetrasomy 12p (mosaicism)

Incidence and carrier frequency

• Very rare disorder
• Affects males and females in equal numbers
• >30 cases reported in the literature

Risk to various family members

• Sporadic inheritance, extremely rare
• No increased recurrence risk

Clinical features

• Typical findings:
• Hypotonia
• sparse scalp hair
• a high forehead with frontal bossing
• a coarse face
• an abnormally wide space between the eyes
• broad nasal bridge
• highly arched palate
• epicanthal folds
• large ears with lobes that are thick and protrude outward.
• Additional features many include:
• congenital heart defects
• diaphragmatic hernia
• hypopigmentation
• extra nipples
• seizures
• droopy upper eyelids
• strabismus
• contractures
• cognitive delays, speech delays
• mental retardation
• stenosis of the external auditory canal
• abnormal opening in the anus
• hypoplastic lung
• abnormalities of the genitourinary system
• skeletal malformations.

Testing/Diagnosis

• the chromosome abnormality in Pallister-Killian Mosaic Syndrome is limited to specific cell types
• mechanism and parental origin of the isochromosome 12p can usually not be determined
• diagnosis is usually made from a chromosome study of skin cells (fibroblasts)
• a blood chromosome study usually shows normal chromosomes
• peripheral blood lymphocytes are continually dividing
• they may lose the extra chromosome with their frequent divisions
• fibroblasts normally cycle less frequently, don't lose the extra chromosome
• Other reasons to test skin cells:
• During the 3rd week of fetal development gastrulation determines 3 germ layers
• Ectoderm: gives rise to the epidermis (skin) and central nervous system
• Endoderm: gives rise to the inner lining of the digestive tract and also the linings of tissues that sprout from the digestive tract, such as the respiratory system, liver, and pancreas
• Mesoderm: gives rise to tissues such as bones, muscle, blood, and connective tissue
• If a chromosome error arises after these tissues differentiate, there could be an error in the skin cells that is not present in other tissues that came from other germ layers

Surveillance, management, and treatment options

• There is no specific therapy for individuals with Pallister-Killian Syndrome
• Because of poor prognosis, generally only supportive care
• Affected children may benefit from early intervention programs and special education

Differential diagnoses

• Fryns syndrome

Psychosocial issues

• Grief over loss of "normal baby"
• Shock over unexpected problems
• Worry about prognosis
• Uncertainty about testing and procedures
• Financial considerations, what will treatment cost?
• Who is their support network?
• Effects on relationships (parent/child)
• Concern about telling other family members
• Future reproductive decisions
• Possible disruption of marital relationships or family dynamics

Support groups

• PKS Kids

PO Box 94

Florissant, MO 63032-0094

email: gpeters@pkskids.net

Home page: http://www.pkskids.net

• UNIQUE - Rare Chromosome Disorder Support Group

P.O. Box 2189

Surrey Intl CR3 5GN

Phone #: 4401883 330766

800 #:

e-mail: info@rarechromo.org

Home page: http://www.rarechromo.org

Sources

• National Organization of Rare Diseases http://www.rarediseases.org
• Bianchi, D., Crombleholme, T., and D'Alton, M. Fetology: Diagnosis and Management of the Fetal Patient. New York: McGraw-Hill, 2000.

Notes

The information in this outline was last updated in May 2004.