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Chromosomal abnormalities

Chromosomal abnormalities. Mohammad Khassawneh Assistant Professor of Pediatrics . 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

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Chromosomal abnormalities

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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

  3. 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

  4. 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

  5. When to suspect it • Unexplained infertility/ balanced translocation • Multiple abortion >2 • Prior case of defective baby

  6. 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%).

  7. 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

  8. 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)

  9. 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

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

  11. Trisomy 18 • Small face with prominant occiput • Small sternum and pelvis • Flexion deformity of the finger • VSD and horseshoe kidney

  12. 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

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

  14. Trisomy 13 • Midline brain defect • Malformed ear • Microophalmos and coloboma • Scalp defect

  15. 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

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

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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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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