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.