These defects include: brain atrophy, agenesis of the corpus callosum, polymicrogyria of the brain, and/or spot calcifications in the brains lateral sulcus; deafness and/or blindness; autonomic nervous system dysfunctions such as anhidrosis, hypohidrosis, and/or episodic spells of hyperventilation interspersed with breath-holding; symptoms of spinal cord malformations; profound or less commonly mild to severe intellectual disability; epileptic seizures; heart and/or anal defects; diaphragmatic hernias; marked muscle weakness; supernumerary nipples; abnormal facial features such as frontal bossing, high frontal hairline, balding around the temple and frontal areas, sparse eyebrows and lashes, hypertelorism, small and flat nose, full cheeks, long philtrum, large mouth with downturned corners, thin cupids bow-shaped upper lip, micrognathia (i.e. undersized jaw), disformed ears that are low-set, thick eyebrows, and/or prominent lips and chin; abnormal oral/dental features such as enlarged tongue, overgrowth of the alveolar ridge and/or gums, delayed teeth eruption, and/or missing or double teeth; patchy skin depigmentations; skeletal anomalies such as limb shortening, lymphedema, increased soft tissues in the extremities, short/broad palms and/or fingers, and/or clinodactyly of the fifth fingers or toes; excessive prenatal and birth weights followed by postnatal declines in growth rates; delayed closure of the anterior fontanel; and/or delayed puberty in males but not females. Causes
PKS is caused by an sSMC that consists of two copies or, less commonly, four copies of the genetic material in the p arm of chromosome 12.
Diagnosis
Prenatal diagnosis
PKS is commonly diagnosed by detecting its causative sSMC as defined by identifying the overexpression of its genetic material. This method has detected the sSMC and therefore diagnosed a fetus as having PKS based on genomic analyses of fetal skin fibroblasts, placenta chorionic villi, cells isolated from the amniotic fluid, fibroblasts isolated from the fetuss umbilical cord, and cells isolated from the fetuss umbilical cord blood. PKS can also be diagnose using fetal ultasound imaging methods. Ultrasound imaging in PKS commonly find fetuses that are too large for their gestational age, contain polyhydramnios (excess amniotic fluid in their amniotic sacs), and have rhizomelic limbs (shortening of the proximal part of the limbs). Less commonly, the imaging evidences diaphragmatic hernias and/or various other major PKS structural malformations. In most cases, however, the ultrasound findings are not diagnostic of PKS. Furthermore, ultrasound diagnoses is best applied in the second or third pregnancy trimester when structural anomalies are more clearly defined and detectable.Because the prenatal diagnosis of PKS using the methods just cited is difficult, often indecisive, and/or best employed later in a womans pregnancy, prenatal cell-free DNA screening (cfDNA screening), also known as noninvasive prenatal screening, has been used to diagnose PKS. This method can diagnose PKS in 10 week and older fetuses. In cfDNA screening, DNA from a mothers blood is extracted and screened for the presence of specific chromosome abnormalities such as those associated with the Down syndrome, Patau syndrome (also termed trisomy 13), and Edwards syndrome (also termed trisomy 18).