Chromosome Disease. The general features in autosome abnormalities are a triad of growth retardation, mental

Transcription

1 Medical Genetics Chapter4 Chromosome Disease

2 Chromosome Disease Clinical feature The general features in autosome abnormalities are a triad of growth retardation, mental retardation, and specific somatic abnormalities. Change of sex chromosome also have the abnormalities and malformations of internal or external genital organs.

3 Chromosome Disease in Clinical Down Syndrome (trisomy 21 syndrome)

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5 Erik Nichols and mother, St. Petersburg, FL

6 Erik Nichols, 21, and his sister, 17-year-old Lindsey, on their graduation from high school. (Saint Petersburg, FL)

7 Chromosome Disease in Clinical Down Syndrome (trisomy 21 syndrome) 1 in 600 ~ 800 newborns Characteristics o Growth retardation ti o Varying degrees of mental retardation o Flattened face o Upward slanting of the eyes with epicanthal folds

8 Chromosome Disease in Clinical Down Syndrome (trisomy 21 syndrome) 1. Trisomy 95%, 47, XX(XY), +21 Caused by non-disjunction of chromosome 21, correlated with age ofmother.

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11 Chromosome Disease in Clinical Down Syndrome (trisomy 21 syndrome) 1. Trisomy 95%, 47, XX(XY), Mosaic 2% ~ 4%, 46/47 3. Unbalance translocation Karyotype of affected: 46, XX(XY), -14, +t(14q21q) Karyotype of balance carrier: 45, XX(XY), -14, -21, +t (14q21q)

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15 Chromosome Disease in Clinical Edwards Syndrome (trisomy 18 syndrome) 1 in 4000 ~ 5000 newborns Characteristics o Growth retardation o Mental retardation o Congenital heart disease o Rocker-bottom feet o fixed flexion deformity of the fingers

16 Chromosome Disease in Clinical Edwards Syndrome (trisomy 18 syndrome) 1 in 4000 ~ 5000 newborns

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20 Chromosome Disease in Clinical Patau Syndrome (trisomy 13 syndrome) 1 in 5000 ~ 7000 newborns Characteristics o Varying degrees of mental retardation o Cleft lip & Cleft palate o Polydactyly (postaxial) o Equinovarus

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23 Chromosome Disease in Clinical 5p - Syndrome (Cat Cry syndrome) 1 in newborns Characteristics o Round, moon-shaped face o Cry of the cat o Varying degrees of mental retardation o Low set ears

24 46, XX(XY), ) del ( 5 ) ( p15 )

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26 Chromosome Disease in Clinical Turner Syndrome (45, X) 1 in 2500 liveborn females Characteristics o Short stature & Webbed neck o Ovarian dysgenesis, primary amenorrhea, infertility o Absence of secondary sex characteristics o Underdeveloped breasts; wide nipples

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28 Background: Turner s Syndrome Described in 1938 by Henry Turner Cause isolated in 1960 (loss of one/part of one sex chromosome) Physical Symptoms: Short Stature (mean height < 5 feet) Failure to develop secondary sex characteristics Maldeveloped Ovaries (infertility; high risk of ovarian cancer) Variety of medical problems: cardiovascular, kidney, pancreas, skeletal, thyroid: MARKED VARIABLE EXPRESSIVITY Minor physical anomalies: webbed neck, low set ears, puffy hands and feet: MARKED VARIABLE EXPRESSIVITY Behavioral Symptoms: Normal intelligence Normal personality (problems of self-esteem esteem and body image that may be associated with physical anomalies) Lowered spatial-visualization and quantitative reasoning? Higher stereotypical feminine interests

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34 Chromosome Disease in Clinical Trisomy X syndrome (47, XXX) 1 in 1000 liveborn females 1 in 250 psychopath of females Two of the three X chromosomes are inactivated.

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36 Chromosome Disease in Clinical Klinefelter syndrome (47, XXY) 1 in 800 males 1 in 100 mentally retarded males 1 in 10 infertile males o Tall with disproportionately long arms/legs o Poorly developed secondary sex characteristics o Testicular dysgenesis

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38 Chromosome Disease in Clinical XYY syndrome (47, XXY) 1 in 750 ~ 1500 males 1 in 30 male prison populations o Tall stature >180 cm: 1/200 >190 cm: 1/30 >200 cm: 1/10 o Predisposition to violent, criminal behavior

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40 Chromosome Disease in Clinical Fragile X chromosome syndrome (Fra X) 1 in 1250 males Characteristics o Show mild to severe mental retardation o Large, protruding ears o Enlarged testes o Narrow face with a prominent chin o Behavioral problems

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