Chromosomal abnormalities
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Transcript of Chromosomal abnormalities
Chromosomal abnormalities.
Valmiki Seecheran.Year V | MBBS.
Introduction.
• A chromosome anomaly/ mutation is a missing, extra or irregular portion of chromosomal DNA.
• Error usually occurs in cell division following meiosis/ mitosis.
Common types.
• Down’s syndrome.• Turner’s syndrome.• Patau’s syndrome.• Edward’s syndrome.
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.
Epidemiology.
• 1 per 1000 births.
Down’s syndrome – Trisomy 21.
Down’s syndrome – Trisomy 21.
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.
Screening.
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.
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.
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.
Turner’s syndrome.
Kleinfelter vs. Turner’s syndrome.
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.
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.
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.
Patau’s syndrome. (Trisomy 13)
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)
Diagnosis.
• Based on clinical findings.• Fetal chromosome testing will show trisomy
13.• Quad screen does not provide reliable means
of screening.
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.
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.
Signs & Symptoms.
• VSD, ASD, PDA.• Omphalocele – intenstines protruding outside
the body.• Esophegeal atresia.• MR – developmental delyas.• Feeding difficulties.• Arthrogryposis (multiple joint contractures at
birth).
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.
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.
Thank you.