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Chromosomal abnormalities

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Chromosomal abnormalities

  1. 1. Chromosomal abnormalities. Valmiki Seecheran. Year V | MBBS.
  2. 2. Introduction. • A chromosome anomaly/ mutation is a missing, extra or irregular portion of chromosomal DNA. • Error usually occurs in cell division following meiosis/ mitosis.
  3. 3. Common types. • Down’s syndrome. • Turner’s syndrome. • Patau’s syndrome. • Edward’s syndrome.
  4. 4. Down’s syndrome – Trisomy 21. • Mental abilities similar to a 8-9 year old. – IQ (50-70). • Poor immune function. • Developmental delays. • Increased risk of: – CHD. – ASD & VSD (80%). – Leukaemia. –Up to 15x more common. (ALL & AML). – Thyroid disorders. – Hypothyroidism (50%) – Mental illnesses.
  5. 5. Epidemiology. • 1 per 1000 births.
  6. 6. Down’s syndrome – Trisomy 21.
  7. 7. Down’s syndrome – Trisomy 21.
  8. 8. Screening. • All pregnant women should be screen regardless of age. • Can be used in combination to increase detection rate. • Amniocentesis/ chorionic villous sampling is required to confirm diagnosis. • Screening in 1st and 2nd trimester is better than just screening in 1st trimester.
  9. 9. Screening.
  10. 10. Diagnosis. • Based on physical appearance at birth. • Chromosomal analysis to determine if translocation is present and also help predict the risk of the child’s parent with future offspring.
  11. 11. Management • Physicians & parents should be aware of the range of psychomotor potential. • Usual immunizations should be performed. • Surgical management of associated conditions should be provided. • Regular screening is necessary to diagnose epilepsy, hypothyroidism, auditory and visual loss.
  12. 12. Turner’s syndrome. • 45,X - absence of an entire sex chromosome, Barr body. • 1 in 2000, 1-500 phenotypic females. • Short stature, low-set ears, webbed necks. • Girls experience gonadal dysfunction – amenorrhea & sterility. • CHD, hypothyroidism, diabetes, auditory- visual problems and auto-immune diseases.
  13. 13. Turner’s syndrome.
  14. 14. Kleinfelter vs. Turner’s syndrome.
  15. 15. Diagnosis. • Postnatal. – Diagnosed at birth due to heart problems, unusually wide neck or swelling of hands and feets. – Undeveloped puberty. • Prenatal. – Amniocentesis or chorionic villus sampling. – Abnormal ultrasound findings – heart defect, kidney abnormality, hygroma, ascites. – Triple/quadruple maternal serum screen.
  16. 16. Treatment. • Most people live long and healthy lives. • Growth hormone/estrogen replacement therapy are usually required. • High risk of keloid formations – cosmetic surgery. • Multi-disciplinary team for screening – cardiologist, endocrinologist, nephrologist, psychologist.
  17. 17. Patau’s syndrome. (Trisomy 13) • Some/ all of the cells contain extra genetic material from chromosome 13. • Nondisjunction of chromosomes during meiosis. • 1 in 10,000.
  18. 18. Patau’s syndrome. (Trisomy 13)
  19. 19. Patau’s syndrome. (Trisomy 13) • Other. – VSD/PDA. – Dextrocardia – Single umbilical artery. • Urogenital. – Abnormal genitalia. – Kidney defects. • MBJ. – Polydactyly. – Low set ears. – Cyclopia. – Cleft palate. • CNS. – Microcephaly. – Meningomyelocele. – MR/motor disorder. – Holoprosencephaly (failure of the forebrain to divide)
  20. 20. Diagnosis. • Based on clinical findings. • Fetal chromosome testing will show trisomy 13. • Quad screen does not provide reliable means of screening.
  21. 21. Treatment & Prognosis. • Case-by-case basis and depends on individual circumstances. • More than 80% of children die within first year of life. • Surgery may be necessary to repair heart defects or cleft lip/palate. • Physical/occupational and speech therapy will help individuals maximise their potenial.
  22. 22. Edward’s syndrome. Trisomy 18. • Presence of all or part of an extra 18th chromosome in cells. • Nondisjunction during meiosis. • 1 in 6000 – most are females (80%). • Low rate of survival – heart abnormalities, kidney malformations.
  23. 23. Signs & Symptoms. • VSD, ASD, PDA. • Omphalocele – intenstines protruding outside the body. • Esophegeal atresia. • MR – developmental delyas. • Feeding difficulties. • Arthrogryposis (multiple joint contractures at birth).
  24. 24. Signs & Symptoms. • Similar to Patau’s. • Microcephahly • Micrognathia (small jaw). • Cleft lip/palate. • Narrow eyelid folds – palpebral fissures. • Ocular hypertelorism – wide space eyes. • Undeveloped fingers/ nails. • Clubfoot/ Rocker-bottom foot. • Undescended testicles. • Choroid plexus cysts – pockets of fluid on the brain.
  25. 25. Treatment. • Supportive. • Treat infections as appropriate. Sepsis is a continuous concern. • Nasogastric/gastrostomy supplmentation for feeding problems. • Multifaceted team – cardiologist, neonataologist, ophthalmologist, orthopaedist, psychologist, speech language pathologist, • Genetic counselling.
  26. 26. Thank you.

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