Chromosome Syndromes

By Naader Khan and Matt Bernal

Trisomy 16Three copies of chromosome 16Most common chromosomal cause of miscarriage Mosaic Trisomy 16:

◦ Rare disorder where in which an extra chromosome 16 is present in some but not all of the cells

◦ Causes intrauterine growth retardation (IUGR) and congenital heart defects Mosaic Trisomy 16 Confimed to the Placenta:

◦ Chromosome 16 abnormality is believed to be present only in the placental tissues

Uniparental Disomy of Chromosome 16: ◦ Chromosome appears normal but both copies have originated from just one

of the two parentsTrisomy 16 can also be caused by a mutation

Trisomy 21 Also known as Down Syndrome Most common chromosome syndrome in born babies Facts about Down Syndrome:

◦ A genetic condition in which a person has 47 chromosomes instead of 46

◦ Extra copy of 21 chromosome◦ Causes problems in which the body and the brain

develop

Trisomy 21(Down Syndrome) Symptoms

Decreased muscle tone at birth Flattened nose Small ears Small mouth Upward slanting eyes Wide, short hands with short fingers Single crease in palm of hand White spots on the colored part of the eye 1/800 People have Down Syndrome Most common genetic cause of mental disability

Down Syndrome Diagnostic Criteria

Diagnosis can be made via chromosome analysisAminocentesis

◦Thin needle is inserted through the abdominal wall and a sample of aniotic fluid is taken which is analyzed for chromosome anomalies

Chorionic villus sampling (CVS)◦Collection of chorionic villus cell sample which is

analyzed for deviationsPercutaneous umbilical blood sampling(PUB)

◦Fetal blood taken from umbilical cord using a needle. Blood sample is examined for chromosome abnormalities

Trisomy 18Also known as “Edwards syndrome’’Extra copy of chromosome 18Occurs on average every 1 out of 6,000 birthsSympotms:

◦Low birth weight◦A small jaw and mouth◦Abnormally shaped small head◦Overlapping fingers◦Clenched fist

Trisomy 13Known as “Patau Syndrome’’Extra copy of chromosome 13Occurs 1 out of every 10,000 newbornsMore than 80% of children die in the first

yearTreatment varies from child to child based

on different symptoms

Symptoms of Trisomy 13Clenched handsClose set eyesDecreased muscle toneExtra finger or toesLow-set earsScalp defectsSmall eyesSmall head and lower jawCleft lip or palate

Monosomy XAlso known as “Turner syndrome’’Condition only occurs in femalesMost commonly female patient only has one x

chromosomeOccurs about 1 out of 2,000 birthsCan be diagnosed at any stage of lifeInfants often have swollen hands and feet

complicationsArthritisCataractsDiabetesHeart defectsHigh blood pressureKidney problemsObesityEar infections

XXY SyndromeAlso known as “Klinefelter syndrome”Only affects malesExtra x chromosome instead of one X and

one YOccurs in 1 out 1,000 malesSome males are given testosterone in

order to be treated

Symptoms of klinefelter syndrome

Sparse body hairEnlarged breastWide hipsVoices may not be deepCannot father children

Sources http://www.trisomy16.org/about/what_are_doc16.html http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH000199

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http://www.medicinenet.com/trisomy_18/page3.htm#how_is_trisomy_18_diagnosed

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001417/

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002625/

http://www.medicinenet.com/trisomy_18/page3.htm#how_is_trisomy_18_diagnosed

http://www.medicinenet.com/down_syndrome/page4.htm#how_is_the_diagnosis_of_down_syndrome_made