National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Pallister-Killian mosaic syndrome



Other Names:
Chromosome 12, Isochromosome 12p syndrome; Killian syndrome; Killian Teschler-Nicola syndrome; Chromosome 12, Isochromosome 12p syndrome; Killian syndrome; Killian Teschler-Nicola syndrome; Pallister mosaic syndrome; Teschler-Nicola Killian syndrome; Tetrasomy 12p, mosaic; Pallister Killian syndrome; PKS See More
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Pallister-Killian mosaic syndrome is a multi-system disorder that is characterized by extremely weak muscle tone (hypotonia) in infancy and early childhood, intellectual disability, distinctive facial features, sparse hair, areas of unusual skin coloring (pigmentation), and other birth defects. The signs and symptoms of Pallister-Killian mosaic syndrome can vary, although most documented cases of people with the syndrome have severe to profound intellectual disability and other serious health problems.[1]

Pallister-Killian mosaic syndrome is usually caused by the presence of an abnormal extra chromosome 12 called isochromosome 12p. An isochromosome is a chromosome with two identical arms. Normal chromosomes have one long (q) arm and one short (p) arm, but isochromosomes have either two q arms or two p arms. Isochromosome 12p is a version of chromosome 12 made up of two p arms. Cells normally have two copies of each chromosome, one inherited from each parent. In people with Pallister-Killian mosaic syndrome, cells have the two usual copies of chromosome 12, but some cells also have the isochromosome 12p. These cells have a total of four copies of all the genes on the p arm of chromosome 12. The extra genetic material from the isochromosome disrupts the normal course of development, causing the characteristic features of this disorder.[1]

Although Pallister-Killian mosaic syndrome is usually caused by an isochromosome 12p, other, more complex chromosomal changes involving chromosome 12 are responsible for the disorder in rare cases.[1]

Treatment depends upon the specific symptoms present in each individual. Treating medical and developmental problems early can help to optimize outcome.[2]
Last updated: 8/8/2016

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 95 |
Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Cachexia
Wasting syndrome
0004326
Delayed eruption of teeth
Delayed eruption
Delayed teeth eruption
Delayed tooth eruption
Eruption, delayed
Late eruption of teeth
Late tooth eruption
[ more ]
0000684
Delayed skeletal maturation
Delayed bone maturation
Delayed skeletal development
[ more ]
0002750
Downturned corners of mouth
Downturned corners of the mouth
Downturned mouth
[ more ]
0002714
Everted lower lip vermilion
Drooping lower lip
Outward turned lower lip
[ more ]
0000232
Hypohidrosis
Decreased ability to sweat
Decreased sweating
Sweating, decreased
[ more ]
0000966
Intellectual disability, severe
Early and severe mental retardation
Mental retardation, severe
Severe mental retardation
[ more ]
0010864
Joint hyperflexibility
Joints move beyond expected range of motion
0005692
Long philtrum 0000343
Muscular hypotonia
Low or weak muscle tone
0001252
Ptosis
Drooping upper eyelid
0000508
Reduced tendon reflexes 0001315
Short neck
Decreased length of neck
0000470
Short stature
Decreased body height
Small stature
[ more ]
0004322
Sparse and thin eyebrow
Thin, sparse eyebrows
0000535
Sparse hair 0008070
Thick upper lip vermilion
Full upper lip
Increased volume of upper lip
Plump upper lip
Prominent upper lip
Thick upper lip
[ more ]
0000215
Thin upper lip vermilion
Thin upper lip
0000219
30%-79% of people have these symptoms
Anteverted nares
Nasal tip, upturned
Upturned nasal tip
Upturned nose
Upturned nostrils
[ more ]
0000463
Coarse facial features
Coarse facial appearance
0000280
Frontal bossing 0002007
Hypertelorism
Wide-set eyes
Widely spaced eyes
[ more ]
0000316
Prominent forehead
Pronounced forehead
Protruding forehead
[ more ]
0011220
Short nose
Decreased length of nose
Shortened nose
[ more ]
0003196
Telecanthus
Corners of eye widely separated
0000506
Upslanted palpebral fissure
Upward slanting of the opening between the eyelids
0000582
5%-29% of people have these symptoms
Abnormal soft palate morphology 0100736
Anal atresia
Absent anus
0002023
Strabismus
Cross-eyed
Squint
Squint eyes
[ more ]
0000486
Percent of people who have these symptoms is not available through HPO
Anal stenosis
Narrowing of anal opening
0002025
Anhidrosis
Lack of sweating
Sweating dysfunction
[ more ]
0000970
Anteriorly placed anus 0001545
Aortic valve stenosis
Narrowing of aortic valve
0001650
Aplasia of the upper vagina
Absent upper vagina
0012673
Aplasia of the uterus
Absent uterus
uterus absent
[ more ]
0000151
Atrial septal defect
An opening in the wall separating the top two chambers of the heart
Hole in heart wall separating two upper heart chambers
[ more ]
0001631
Bifid uvula 0000193
Broad foot
Broad feet
Wide foot
[ more ]
0001769
Broad palm
Broad hand
Broad hands
Wide palm
[ more ]
0001169
Cataract
Clouding of the lens of the eye
Cloudy lens
[ more ]
0000518
Clinodactyly of the 5th finger
Permanent curving of the pinkie finger
0004209
Coarctation of aorta
Narrowing of aorta
Narrowing of the aorta
[ more ]
0001680
Congenital diaphragmatic hernia 0000776
Congenital hip dislocation
Dislocated hip since birth
0001374
Cryptorchidism
Undescended testes
Undescended testis
[ more ]
0000028
Depressed nasal bridge
Depressed bridge of nose
Flat bridge of nose
Flat nasal bridge
Flat, nasal bridge
Flattened nasal bridge
Low nasal bridge
Low nasal root
[ more ]
0005280
Epicanthus
Eye folds
Prominent eye folds
[ more ]
0000286
Feeding difficulties
Feeding problems
Poor feeding
[ more ]
0011968
Flexion contracture
Flexed joint that cannot be straightened
0001371
Full cheeks
Apple cheeks
Big cheeks
Increased size of cheeks
Large cheeks
[ more ]
0000293
Generalized hypotonia
Decreased muscle tone
Low muscle tone
[ more ]
0001290
Hearing impairment
Deafness
Hearing defect
[ more ]
0000365
Hyperpigmented streaks 0007572
Hypertonia 0001276
Hypertrophic cardiomyopathy
Enlarged and thickened heart muscle
0001639
Hyperventilation
Rapid breathing
0002883
Hypopigmented streaks 0007535
Hypoplastic labia majora
Small labia majora
Underdeveloped vaginal lips
[ more ]
0000059
Hypospadias 0000047
Inguinal hernia 0000023
Intellectual disability, profound
IQ less than 20
0002187
Intestinal malrotation 0002566
Kyphoscoliosis 0002751
Macrocephaly
Increased size of skull
Large head
Large head circumference
[ more ]
0000256
Macroglossia
Abnormally large tongue
Increased size of tongue
Large tongue
[ more ]
0000158
Macrotia
Large ears
0000400
Mesomelia
Disproportionately short middle portion of limb
0003027
Mesomelic/rhizomelic limb shortening 0005026
Micrognathia
Little lower jaw
Small jaw
Small lower jaw
[ more ]
0000347
Myopia
Close sighted
Near sighted
Near sightedness
Nearsightedness
[ more ]
0000545
Obesity
Having too much body fat
0001513
Omphalocele 0001539
Patent ductus arteriosus 0001643
Postaxial foot polydactyly
Extra toe attached near the little toe
0001830
Postaxial hand polydactyly
Extra little finger
Extra pinkie finger
Extra pinky finger
[ more ]
0001162
Postnatal microcephaly 0005484
Proptosis
Bulging eye
Eyeballs bulging out
Prominent eyes
Prominent globes
Protruding eyes
[ more ]
0000520
Pulmonary hypoplasia
Small lung
Underdeveloped lung
[ more ]
0002089
Renal cyst
Kidney cyst
0000107
Renal dysplasia 0000110
Seizure 0001250
Short phalanx of finger
Short finger bones
0009803
Short toe
Short toes
Stubby toes
[ more ]
0001831
Single transverse palmar crease 0000954
Small scrotum
Underdeveloped scrotum
0030276
Somatic mosaicism 0001442
Sparse anterior scalp hair
Sparse scalp hair at front of head
Thin scalp hair at front of head
[ more ]
0004768
Sparse eyelashes
Scant eyelashes
Scanty eyelashes
Thin eyelashes
[ more ]
0000653
Stenosis of the external auditory canal
Narrowing of passageway from outer ear to middle ear
0000402
Stillbirth
Stillborn
0003826
Supernumerary nipple
Accessory nipple
0002558
Umbilical hernia 0001537
Ventricular septal defect
Hole in heart wall separating two lower heart chambers
0001629
Webbed neck
Neck webbing
0000465
Wide nasal bridge
Broad nasal bridge
Broad nasal root
Broadened nasal bridge
Increased breadth of bridge of nose
Increased breadth of nasal bridge
Increased width of bridge of nose
Increased width of nasal bridge
Nasal bridge broad
Wide bridge of nose
Widened nasal bridge
[ more ]
0000431
Showing of 95 |
Last updated: 7/1/2020

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • Orphanet lists international laboratories offering diagnostic testing for this condition.

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources


Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnoses include trisomy 12p and Fryns syndrome (see these terms). Antenatal diagnosis may be possible through ultrasound examination revealing abnormal findings such as diaphragmatic hernia, polyhydramnios, hydrops fetalis, cardiac malformations, short limbs, and other, leading to amniocentesis and chromosomal diagnosis.
Visit the Orphanet disease page for more information.

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease


Living with a genetic or rare disease can impact the daily lives of patients and families. These resources can help families navigate various aspects of living with a rare disease.

Financial Resources


These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Pallister-Killian mosaic syndrome. This website is maintained by the National Library of Medicine.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.
  • Unique is a source of information and support for families and individuals affected by rare chromosome disorders. Click on the link to view information about Pallister-Killian mosaic syndrome.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Pallister-Killian mosaic syndrome. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.


  1. Pallister-Killian mosaic syndrome. Genetics Home Reference. June 2016; https://ghr.nlm.nih.gov/condition/pallister-killian-mosaic-syndrome.
  2. Dr. Ian Krantz. Recommended Clinical Evaluations for the Child with PKS. PKS Kids. 2015; http://www.pkskids.net/PKSClinicalRecomendations2012-08.pdf.