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Chromosomal abnormalities Mohammad Khassawneh Assistant Professor of Pediatrics.

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1 Chromosomal abnormalities Mohammad Khassawneh Assistant Professor of Pediatrics

2 introduction  Normal human cells contain 23 pairs of chromosomes  This includes one pair of sex chromosome XX or XY  During cell division we can identify chromosomes  Lymphocytes incubated for 2-3 days or uncultured bone marrow in 4-24 hours

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4 continue  Haploid: set of 23 chromosomes  Diploid: normal number of 46 chromosomes  Aneuploidy: less than an even multiple of 23 usually is 45 or 47 and rarely 48,49  Triploidy: 69 chromosomes  Mosaicism  Abnormal in deletion and translocation(balanced and unbalanced)Balanced

5 Incidence  The earlier the abortion the more likely to be chromosomal  50% of spontanous abortion are chromosomal abnormal  Mostly triploidy. 45 XO, trisomy 16  98% of fetus with turner abort  Generally 6/1000 the incidence of chromosomal abnormalities

6 When to suspect it  Unexplained infertility/ balanced translocation  Multiple abortion >2  Prior case of defective baby

7 When to suspect it…continue  Presence of congenital anomalies  45% have minor single anomalies  9% 3 minor anomalies  1.5% HAVE major anomaly  2 or more major anomalies may represent genetic syndrome or chromosomal abnormalities(10%).

8 Down Syndrome  Incidence 1/700  2/3 of down fetus spontaneously abort  Clinical diagnosis depend on gestalt  Trisomy 21 in 94% of cases with extra chromosome from mother mostly(95%)  Risk correlate with maternal age  <25 y/o 1/1600  >40 y/0 1/80  2% are mosaic

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13 Other Clinical features  Hypotonia without weakness  Clinodactaly protruded tongue,small ears,brachycephaly,small up turned nose, depressed nasal bridge.  Mental retardation, socially do better with good environment (Happy children)

14 Clinical issues  Cardiac and GI  Hypothyriodism  Transient leukemoid reaction  Alzheimer’s disease up to 25% over 40 y/o  Early death relate to cardiac dysfunction

15 Trisomy 18  Incidence 1/8000  Overlaps with trisomy 13  Sever Mental retardation  >90% dead in 1 st year

16 Trisomy 18  Small face with prominant occiput  Small sternum and pelvis  Flexion deformity of the finger  VSD and horseshoe kidney

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23 triploidy  Complete extra set of chromosomes  Mostly miscarriages  Fetal wastage skeleton more than cephalic, 2% survive to be recognized  Large hydatidiform placenta  VSD, ASD, Syndactaly  Genital and CNS abnormalities

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25 Trisomy 13  Sever developmetal retardation  Incidence 1/20000  90% dead in the 1 st year

26 Trisomy 13  Midline brain defect  Malformed ear  Microophalmos and coloboma  Scalp defect

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32 Turner syndrome  Most common abnormality in early abortion  Female, short stature, primary amenorrhea, sterility, spares hair and underdeveloped breast  Neonatal: wide spaced nipple, lymphedema, shield chest,  Coarctation of the aorta

33 Continue turner syndrome  Normal IQ scale with difficulty in spatial orientation such as map  Present with short stature or delay sex maturation  Hormonal therapy

34 continue  Mosaisim (15%), remove gonads  Recurrent risk is 1-2%  Noonan syndrom AD, fresh mutation  Pulmonary stenosis, nl stature, microceph, mental retardation

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36 Klinefelter syndrome  20% of aspermic adult male (blocked spermatogenesis  47 XXY in 80% and mosaic in 20%  IQ is 98 (normal) with mild decrease in verbal IQ  Scoliosis, decrease libido may improve with testesterone, gynecomastia

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38 Fragile X Syndrome  Moderate to sever mental retardation  Speech delay, short attention, hyperactivity  Poor motor coordination and mouthing objects  Poor socialization, temper tantrum  Mood disorder (bipolar), schizophrenia

39 Fragile X syndrome  Long protruding ears  Long face and prominent jaw  Flattened nasal bridge  High arch palate  Macroorchidism  Genetic is complex, 80% penetration in male and 30% penetration in female

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41 Genetic imprinting  Means: as genomes pass through miosis it is normal for part of it to change.  During miosis inactive X chromosome become active and changes on fragiloe X gene (imprinting) make it malignant

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43 Angelman syndrome  Sever mental retardation  Inappropriate laughter  Decrease pigmentation of choroid or iris (pale blue eyes)  Ataxia and jerky eye movement  Sever speech proplem  Deletion of b15q11q13, maternal in origin  Paternal uniparental disomy

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45 Prader-willi syndrome  (A fat red faced boy in state of somnolency) Charles Diickens  Early hypotonia  Obesity  Short stature as adult  Almond shaped blue eyes  Mental retardation (mild to moderate)  Narrow hands

46 Chromosomal linked disorder  Smith Lemli opitz syndrome  Low cholesterol  High 7 dehydrocholesterol  Like trsomy 18  CHARGE  Coloboma  Heart  Atresia of choanae  Retarded  Genitalia hypoplasia  Ear anomalies  VATER

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