Congenital heart disease occurs in 50 of patients

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Congenital Heart Disease: Occurs in 50% of patients, most commonly endocardial cushion defects. o Endocardial cushions are embryological structures that form septa between 2 atria and ventricles – can get Primum ASD, VSD (holosystolic murmur – high yield), or mitral regurgitation as endocardial cushion important in mitral valve formation GI anomalies: 5% of patients – duodenal atresia or stenosis (most common), Hirschsprung disease Alzheimer’s: AD occurs early (50s). Amyloid precursor protein (APP) found on chromosome 21, of which there are 3 copies – APP breaks down to form B-amyloid, seen in AD Malignancy: Increased risk, especially Leukemia often occurring in childhood. ALL 10-20x higher, AML M7 subtype (megakaryoblastic leukemia) Meiotic non-disjunction: 2 chromosomes from 1 parent, 1 from another, usually in Meiosis I. In 90% of cases, extra chromosome is maternal, increased risk with advanced maternal age o Rarely caused by Robertsonian translocation – chromosome 21 fuses with another chromosome (10 or 14), so two copies of 21 passed to fetus from 1 parent – no increased risk with advanced maternal age, high recurrence risk within families o Recurring Down Syndrome within families, Robertsonian translocation is cause (high-yield) o Can also be caused (rarely) by mitotic error – error in mitosis of somatic cells after fertilization can cause somatic mosaicism such that some cells are trisomy 21, some normal – can caused milder DS features and not associated with advanced maternal age Definitive pre-natal screening test: fetal karyotype via chorionic villus sample (placental tissue) or amniocentesis (amniotic fluid) invasive, carries risk. Only do if high pre-test probability. Non-invasive tests: Ultrasound, maternal serum testing First-trimester findings: On fetal ultrasound, would see small, poorly-formed nasal bones, nuchal translucency (fluid under back of neck). o Maternal blood: Pregnancy-associated plasma protein-A (PAPP-A) is low with DS – PAPP-A is a glycoprotein produced by placenta. Free or total B-hCG (placental hormone) is higher in DS fetuses 2 nd trimester findings: a-fetoprotein (produced by yolk sac and liver) and estriol (uE3) are reduced in DS fetuses (high AFP = neural tube defect). Inhibin A (made by placenta) and B-hCG increased in DS fetus these are called a “Quad Screen” Trisomy Disorders: All associated with advanced maternal age, meiotic NDJ, intellectual disability, congenital heart defects, and physical deformities Edward and Patau Syndromes are just more severe versions of DS Edward Syndrome (Trisomy 18): 2 nd most common livebirth trisomy. Features include severe intellectual disability, often female (3:1) o Poor intrauterine growth, low birth weight, abnormally shaped head (small with prominent back of skull – occiput), low set ears, small jaw/mouth, clenched fists with overlapping fingers/curved feet (hallmark features) o Congenital heart disease: 50% of cases – VSDs or PDAs o GI defects: 75% of cases (more than DS)- Meckel’s Diverticulum, malrotation, Omphalocele o

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