Chromosome 12p tetrasomy syndrome. Pallister-Killian syndrome. Tetrasomy 12p.
Incidence
Somatic mosaicism. It is a rare and sporadic multiple congenital anomaly/mental retardation syndrome.
Clinical Characteristics
Pallister-Killian syndrome is a rare and sporadic multiple congenital anomaly/mental retardation syndrome characterized by the mosaic tissue-limited presence of a supernumerary 12p chromosome. Patients usually present with pigmentary skin changes, mental retardation, seizures, and characteristic facial abnormalities including hypertelorism, abnormal ears, macrostomia, a broad high forehead, a broad nasal bridge and sparseness of scalp hair. Mechanism(s) of formation of the isochromosome are not well understood. The vast majority of the errors were found to be maternal in origin. Premeiotic mitotic error may be the most likely mechanism for i(12p) formation in this syndrome.Tetrasomy of the short arm of chromosome 12 associated with craniofacial abnormalities with coarse facies, growth and mental deficiency, slow growing hair, and other abnormalities. The adult phenotype is marked mainly by epilepsy, macroglossia, coarse facies, and severe mental retardation.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. Mosaic tetrasomy 12p in skin fibroblasts. Isochromosome often missing in lymphocyte.