Bocian Clinical Syndromes Flashcards
What is triploidy
69 chromosomes
Describe the chromosome constitution of triploidy
69,XXY - 60%
69, XXX - 35%
69, XYY - 5%
Describe the etiology of triploidy
Most (65%) due to dispermy
Many (25%) due to fertilization with a diploid sperm (mitotic failure during meiosis)
Some (10%) due to fertilization with a diploid egg (failure to shed a polar body)
Two types of Trisomy 21 genotype
47, XY, +21
47, XX, +21
Down Syndrome is names for?
Dr. Langdon Down
Symptoms of Down Syndrome
Intellectual disabilities, usually mild to moderate
Typical physical features of down syndrome (6)
- Up-slanting eyes
- Small ears
- Thin, down-turned lips
- Short, broad hands
- Single transverse palmar crease
- 5th finger—single crease or short middle phalanx (middle segment)
Describe the tone of Down Syndrome
Hypotonia (“low tone;” poor muscle tone; “floppiness”)
Down syndrome organ dysfunction?
Congenital heart disease (45%)
Lifespan for Down syndrome
Essentially normal lifespan if there is no serious heart disease or other complication
Three types of chromosome abnormality in Down Syndrome
Nondisjunction
Translocation
Mosaicism
Describe Down Syndrome Nondisjunction
Nondisjunction (3 separate copies of chromosome 21)
a) Most patients (95%) have trisomy due to nondisjunction
Describe Down Syndrome translocation
Relatively few patients (3%) have translocations; t(14;21) is the most common—half are inherited,
half are de novo (occur for the first time in the patient); must do parents’ karyotypes to determine recurrence risk
Describe Down Syndrome Mosaicism
Relatively few patients have mosaicism (2%)
Describe recurrence risk of Down Syndrome
Recurrence risk depends on the mechanism (i.e., nondisjunction vs. de novo translocation vs. inherited translocation) and, in cases of nondisjunction, on the mother’s age at the time of the affected baby’s birth
Trisomy 13 is called?
Patau syndrome
Genotype for Trisomy 13
47, XY, +13
47, XX, +13
Abnormalities of Trisomy 13
Multiple anomalies: cleft lip ± cleft palate, polydactyly (extra fingers or toes),
microphthalmia (small eyes), omphalocele, cardiac anomalies, renal anomalies, etc.
Intellectual level of Trisomy 13
Severe intellectual disabilities
Lifespan of Trisomy 13
Severely shortened lifespan (few reach past 6 months)
Recurrence risk of Trisomy 13
Recurrence risk depends on the mechanism (i.e., nondisjunction vs. de novo translocation vs. inherited translocation) and, in cases of nondisjunction, on the mother’s age at the time of the affected baby’s birth
Trisomy 18 is also called?
Edwards syndrome
Trisomy 18 genotype
47, XY, +18
47, XX, +18
Abnormalities of Trisomy 18
Clenched hand position and typical facial features
Intellectual level of Trisomy 18
Profound intellectual diability
Lifespan of Trisomy 18
Severely shortened lifespan, most die before 1 year
Recurrence risk of Trisomy 18
Recurrence risk depends on the mechanism (i.e., nondisjunction vs. de novo translocation vs. inherited translocation) and, in cases of nondisjunction, on the mother’s age at the time of the affected baby’s birth
Genotype of Turner syndrome
45,X