ABGC 100 Genetic Conditions Exam Questions
and Answers 100% Pass
T13 - ✔✔Nondisjunction; 1 in 12,000
SGA, MCA: hypotelorism, CLP, heart, brain and kidney defects
RR is 1%
T18 - ✔✔Nondisjunction; 1 in 6,000
SGA, MCA: prominent occiput, tightly clenched fingers, heart and brain defects
Choroid plexus cyst on u/s
RR is 1%
T21 - ✔✔MATERNAL nondisjunction (90%); 5% translocation 21;**usually 14**; 2% mosaic T21
1 in 800
Hypotonic, heart (50%) and GI defects common
Mild to moderate ID
Immunodeficiency, leukemia common
Adults at risk for EO-AZD
RR is 1%; Robertsonian ~15-100% for 21;21
AMA = best documented risk factor
47, XXY (Klinefelter) - ✔✔Nondisjunction; may have additional X chr
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,1/500 - 1/1,000
May fail to develop 2ndary sex characteristics (tx testosterone)
Small testes with few or no sperm
Learning disabilities
Recurrence is rare but may happen
Turner - ✔✔45,X karyotype due to nondisjunction or loss of a structurally abnormal X or Y
Mosaics common, with a cell line containing 46 chr w/ structurally abnormal X or Y
1/3,000
May fail to develop 2ndary sex characteristics
Short stature, primary amenorrhea and usually infertile (tx GH and estradiol)
Heart (CoA common) and kidney (horseshoe common)
Congenital lymphedema with redundant nuchal skin
Learning disabilities
Recurrence is rare
47, XYY (Jacob's) - ✔✔XYY karyotype due to nondisjunction
1 in 1,000
Fertile with LD and behavioral concerns
Tall stature
Recurrence is rare
47, XXX - ✔✔Nondisjunction; some have 3+ X
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,1 in 1,000
Fertile
Cognitive impairment
Tall stature
Recurrence rare but may happen
22q11.2 (Velo-cardio-facial syndrome, DiGeorge syndrome) - ✔✔Microdeletion, transmitted as dominant
trait
**90% de novo, 3Mb common deletion**
1/4,000 - 1/6,000
CP (**NO CL**), conotruncal cardiac malformations, Absence of parathyroids (**HYPOcalcemia**)
**Thymus aplasia (immunodeficiency)**
LD and psychiatric disorders
Germline mosaicism possible
Prader-Willi syndrome - ✔✔Genomic imprinting disorder
70% Deletion of the paternal 15q11.2-q13 region
25% Maternal UPD of chr 15
5% Mutation of the imprinting center on chr 15
**Causative gene(s) NOT known**
1/10,000 - 1/25,000
At birth: hypotonic, FTT
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, Childhood: hyperphagia, short stature (tx with GH), obesity, DD and behavioral concerns
Recurrence is rare
Angelman syndrome - ✔✔Genomic imprinting disorder
68% Deletion of the maternal 15q11.2-q13 region
11% **UBE3A** gene mutation (AD)
7% Paternal UPD of chr 15
3% Small imprinting region deletions (AD)
1/12,000 - 1/20,000
Severe DD, seizures, hyperactivity, abnormal gait
Recurrence is rare
Williams syndrome (Williams-Bueren syndrome) - ✔✔Microdeletion of chromosome **7q**11.2
***Deletion of elastin gene***
1 in 7,500
Often born POST-term, SGA and FTT
Neonatal **HYPER-calcemia**
**Supravalvar aortic stenosis (SVAS)**
HTN due to renal artery stenosis
DD with distinctive, outgoing personality
**Some unaffected parents carry a chr 7 inversion that may predispose to the deletion**
Cowden syndrome (PTEN hamartoma syndrome) - ✔✔AD; **LOF**
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and Answers 100% Pass
T13 - ✔✔Nondisjunction; 1 in 12,000
SGA, MCA: hypotelorism, CLP, heart, brain and kidney defects
RR is 1%
T18 - ✔✔Nondisjunction; 1 in 6,000
SGA, MCA: prominent occiput, tightly clenched fingers, heart and brain defects
Choroid plexus cyst on u/s
RR is 1%
T21 - ✔✔MATERNAL nondisjunction (90%); 5% translocation 21;**usually 14**; 2% mosaic T21
1 in 800
Hypotonic, heart (50%) and GI defects common
Mild to moderate ID
Immunodeficiency, leukemia common
Adults at risk for EO-AZD
RR is 1%; Robertsonian ~15-100% for 21;21
AMA = best documented risk factor
47, XXY (Klinefelter) - ✔✔Nondisjunction; may have additional X chr
Page 1/45
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,1/500 - 1/1,000
May fail to develop 2ndary sex characteristics (tx testosterone)
Small testes with few or no sperm
Learning disabilities
Recurrence is rare but may happen
Turner - ✔✔45,X karyotype due to nondisjunction or loss of a structurally abnormal X or Y
Mosaics common, with a cell line containing 46 chr w/ structurally abnormal X or Y
1/3,000
May fail to develop 2ndary sex characteristics
Short stature, primary amenorrhea and usually infertile (tx GH and estradiol)
Heart (CoA common) and kidney (horseshoe common)
Congenital lymphedema with redundant nuchal skin
Learning disabilities
Recurrence is rare
47, XYY (Jacob's) - ✔✔XYY karyotype due to nondisjunction
1 in 1,000
Fertile with LD and behavioral concerns
Tall stature
Recurrence is rare
47, XXX - ✔✔Nondisjunction; some have 3+ X
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,1 in 1,000
Fertile
Cognitive impairment
Tall stature
Recurrence rare but may happen
22q11.2 (Velo-cardio-facial syndrome, DiGeorge syndrome) - ✔✔Microdeletion, transmitted as dominant
trait
**90% de novo, 3Mb common deletion**
1/4,000 - 1/6,000
CP (**NO CL**), conotruncal cardiac malformations, Absence of parathyroids (**HYPOcalcemia**)
**Thymus aplasia (immunodeficiency)**
LD and psychiatric disorders
Germline mosaicism possible
Prader-Willi syndrome - ✔✔Genomic imprinting disorder
70% Deletion of the paternal 15q11.2-q13 region
25% Maternal UPD of chr 15
5% Mutation of the imprinting center on chr 15
**Causative gene(s) NOT known**
1/10,000 - 1/25,000
At birth: hypotonic, FTT
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, Childhood: hyperphagia, short stature (tx with GH), obesity, DD and behavioral concerns
Recurrence is rare
Angelman syndrome - ✔✔Genomic imprinting disorder
68% Deletion of the maternal 15q11.2-q13 region
11% **UBE3A** gene mutation (AD)
7% Paternal UPD of chr 15
3% Small imprinting region deletions (AD)
1/12,000 - 1/20,000
Severe DD, seizures, hyperactivity, abnormal gait
Recurrence is rare
Williams syndrome (Williams-Bueren syndrome) - ✔✔Microdeletion of chromosome **7q**11.2
***Deletion of elastin gene***
1 in 7,500
Often born POST-term, SGA and FTT
Neonatal **HYPER-calcemia**
**Supravalvar aortic stenosis (SVAS)**
HTN due to renal artery stenosis
DD with distinctive, outgoing personality
**Some unaffected parents carry a chr 7 inversion that may predispose to the deletion**
Cowden syndrome (PTEN hamartoma syndrome) - ✔✔AD; **LOF**
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