1-23 Chromosomal Anamolies

Question 1

Trisomy 21

Answer 1

47, X(X/Y), +21

`95% free trisomy

1:600 live births

Hypotonia: low muscle tone, open mouth, protruding tongues, CNS: intellectually disability

Brachycephaly, flat occiput, upward slanting palpebral fissues (upward slanting eyes), epicanthal folds (eye skin fold), round face, eyes: brushfield spots (white dots), small ears with overfolding upper helix

short finders, transverse palmar crease

males infertile, females fertile

ventricular septal defect: VSD

AV canal/endocardial cushion defect: communication between all 4 chambers

cutis marmorate: vascular lacy skin appearance

reduced life expectancy, dementia developed in 40s/50s

Question 2

Most common type of chromosomal rearrangement

Answer 2

non-disjunction

Question 3

Trisomy 13

Answer 3

1:5000 births

malformations found in >50% of cases, more varied phenotype than down syndrome

CNS: holoprosencephaly/incomplete forebrain development, severe mental deficiency, apnea, seizures

Scalp defects: sutures may be wide, anterior fontenelle wide

Clep lip/cleft palate

transverse palmar crease, narrow hyperconvex nails, camptodactyly/ polydactyly next to pinky, prominent heel

Cardiac: VSD, PDA, ASD, dextroposition, many different kinds

Bicornuate uterus, undescended testes

55% mortality at 1 month, 82% 12 months

Question 4

Trisomy 18

Answer 4

1:3000 live births

Malformations found in 50% of cases, more easily recognizable than 13 but less so than 21

Small for gestational age, altered gestational timing, hypoplasia, scrawny, small jaw, prominant occiput, severe intellectual disability, hypertonicity (increased muscle tone), low set malformed ears, clenched hand/overlapping fingers, nails underdeveloped, absent of flexion crease on 5th finger, short big toe, thin ribs

VSD, ASD, patent ductus areteriosus

small pelvis

genitalia: cryptorchidism
mortality: 30% 1 month, 90% by 12 month

Question 5

Turner Syndrome

Answer 5

45, X

1:2500 females

short stature, average intelligence, poor social cognition/visual spatial/motor development

ovarian dysgenesis: “streak ovaries”, sterile, no secondary sex characteristics at puberty

wide carrying angle, shield like chest, epicanthal folds, abnormal ears, low hairline, redundant skin, webbed neck, edema, short 4th metacarpal/metatarsal

cardiac: bicuspid aortic valve, coarctation of aorta

Treatments: daily injections of growth hormones, hormone replacement initiated at time of puberty helps develop secondary sex char

Question 6

williams-beuren syndrome

Answer 6

Microdeletion syndromes: deletion 7q11.23, cannot see on routine karyotype

can detect by FISH

wike spokes of iris, distinctive facies, “loquacious” personality, intellectual disability, hypercalcemia, supravalvular aortic stenosis