Routine prenatal ultrasound evaluation may reveal traits such as abnormal presentation close to due date, rhizomelia, diaphragmatic abnormalities such as hernias, anal defects, and heart malformations, especially ventricular septal defect, all of which are highly suggestive of this syndrome.

After birth, the first sign that draws the clinician's attention is hypotonia, that may be severe enough to interfere with respiration and deglutition. Newborns and children also have a specific phenotype, characterized by facial dimorphism: "coarse" facies, high forehead, sparse lashes and eyebrows, shallow supraorbital ridges, hypertelorism, flat nasal bridge, long philtrum [1], short neck, low-implanted ears, large tongue, hypoplastic nails and small hands, sparse hair and areas of unusual skin pigmentation [2]. The hypotonia persists as the child grows older, leading to difficulties in sitting, standing, and mobility. The clinical picture is completed by intellectual disability, manifested as severe or profound mental deficiency, deafness, seizures, hypoplastic lungs and speaking difficulties. Other abnormalities such as cleft palate, supernumerary nipples, genital malformations, auditory canal stenosis, extra fingers or toes or bald scalp areas may also occur. The neurologic prognosis of these patients is grim, with severely disabled motor capabilities and incontinence [3] [4].

Diaphragmatic hernias are considered to be highly specific and are frequent [5].

These traits may not be present in all affected individuals or may be less prominent. The severity of genotype abnormalities does not correlate with the clinical features of the newborn [6]. In other cases, different sides of the body may be affected unevenly.

The diagnosis relies on the detection of the mosaic tetrasomy of isochromosome 12p. This can be done by various techniques, performed on different cell types. The most reliable choice is to perform an amniocentesis, as i(12p) is found in all amniocytes in fetuses suffering from this condition [7]. Similarly, all newborn bone marrow cells have this trait [8], whereas a variable percentage of fibroblasts, lung, liver, testes and spleen cells exhibit the abnormality, hence the "tissue-specific mosaicism" term. Lymphocytes are infrequently affected, therefore blood karyotype may not be a reliable method to diagnose this illness, especially due to the high turnover of blood cells. Fibroblasts may be obtained from buccal smears or skin areas with different pigmentation. The percentage of i(12p) cells does not correlate with disease severity [9]. Furthermore, the number of detectable diseased cells decreases as the patient ages [10].

Fluorescence in situ hybridization (FISH) [11] [12] and interphase FISH are reliable diagnostic methods [13]. Other methods include karyotype analysis, array comparative genomic hybridization (CGH) and chromosomal microarray. A normal karyotype of blood cells does not exclude the diagnose. In case clinical doubt persists, newer diagnostic methods, such as spectral karyotyping and multiplex-FISH may shed light over the case [14].

There is no cure for PKS, so treatment focuses on managing symptoms and improving quality of life. A multidisciplinary approach is often necessary, involving pediatricians, neurologists, cardiologists, and other specialists. Physical therapy can help improve motor skills, while speech and occupational therapy can support communication and daily living skills. Regular monitoring and treatment of associated health issues, such as heart defects or seizures, are also important.

The prognosis for individuals with PKS varies widely depending on the severity of symptoms and associated health issues. While some individuals may have significant developmental and health challenges, others may achieve a degree of independence with appropriate support. Early intervention and tailored therapies can improve outcomes, but ongoing care and support are typically required throughout life.

PKS is caused by the presence of an extra isochromosome 12p in some cells. This genetic anomaly occurs sporadically, meaning it usually happens by chance and is not inherited from the parents. The exact mechanism leading to the formation of the extra chromosome is not fully understood, but it is believed to occur during cell division in early embryonic development.

PKS is an extremely rare condition, with an estimated prevalence of less than 1 in 20,000 live births. Due to its rarity and the variability of symptoms, it is likely underdiagnosed. The condition affects both males and females equally and has been reported in various ethnic groups worldwide.

The pathophysiology of PKS involves the presence of extra genetic material from chromosome 12, which disrupts normal development and function. The mosaic pattern means that not all cells have the extra chromosome, leading to variability in symptoms. The specific genes on chromosome 12p responsible for the features of PKS are not fully identified, but the extra genetic material is believed to interfere with normal cellular processes.

Currently, there is no known way to prevent PKS, as it occurs sporadically and is not inherited. Genetic counseling may be beneficial for families with a child diagnosed with PKS to understand the condition and discuss any potential risks for future pregnancies, although the risk of recurrence is generally low.

Pallister-Killian Syndrome is a rare genetic disorder caused by an extra isochromosome 12p, leading to a range of physical, developmental, and intellectual challenges. Diagnosis involves clinical evaluation and genetic testing, while treatment focuses on managing symptoms through a multidisciplinary approach. Prognosis varies, and ongoing support is essential for improving quality of life. The condition occurs sporadically, with no known prevention methods.

For families and individuals affected by PKS, understanding the condition can be challenging. It is important to know that PKS is a rare genetic disorder that affects development and health in various ways. While there is no cure, many therapies and interventions can help manage symptoms and improve quality of life. Support from healthcare professionals, as well as connecting with other families through support groups, can provide valuable resources and encouragement.

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