Genetics

Question 1

A newborn is delivered at 38 weeks via spontaneous vaginal delivery. On physical examination, the baby has a cleft lip and cleft palate. The mother had no significant illness during pregnancy, and there was no history of teratogen exposure. Which of the following best describes this condition?

A. Malformation/Anomaly
B. Malformation Sequence
C. Malformation Syndrome
D. Disruption

Answer 1

A. Malformation/Anomaly

Rationale:

Malformation refers to a primary defect in organ development that occurs before 10 weeks of gestation.
Cleft lip and palate is a classic example of malformation because it results from a defect in embryologic development.
It is not a sequence (B) because it does not stem from a prior defect.
It is not a syndrome (C) because there are no additional systemic abnormalities.
It is not a disruption (D) because tissue was never normally formed before being destroyed.

Question 2

Which of the following best describes a malformation sequence?

A. Anomalies that occur due to a single primary defect that triggers multiple defects
B. A pattern of anomalies with a common genetic or environmental cause
C. A group of anomalies that occur together without a known cause
D. A single isolated structural defect due to abnormal development

Answer 2

A. Anomalies that occur due to a single primary defect that triggers multiple defects

Rationale:

Malformation sequences occur when one primary defect leads to secondary anomalies (a chain reaction).
Example: Myelomeningocele (neural tube defect) → Talipes Equinovarus (Clubfoot) due to abnormal fetal positioning.
Syndrome (B) describes conditions like Down Syndrome (genetic cause).
Association (C) describes VACTERL, where anomalies co-occur but have no known cause.
Malformation (D) is a primary defect but does not necessarily cause additional defects.

Question 3

A newborn presents with a lumbar neural tube defect (Myelomeningocele), and further examination reveals clubfoot (Talipes Equinovarus). The findings suggest that the foot deformity developed secondary to the neural tube defect. What is the most appropriate classification of this condition?

A. Malformation/Anomaly
B. Malformation Sequence
C. Malformation Syndrome
D. Deformation

Answer 3

B. Malformation Sequence

Rationale:

A malformation sequence results when one primary defect leads to secondary defects.
The primary defect here is Myelomeningocele (lumbar neural tube defect).
The secondary defect is Talipes Equinovarus (clubfoot), which occurs due to abnormal fetal positioning caused by the primary defect.
It is not an isolated anomaly (A) since it involves multiple linked defects.
It is not a syndrome (C) because syndromes have multiple causes.
It is not deformation (D) since the structure was abnormal from the start.

Question 4

Which of the following best describes malformation syndrome?

A. A group of anomalies with a single genetic or environmental cause
B. A pattern of defects caused by an initial malformation leading to a cascade of anomalies
C. An isolated structural defect due to abnormal embryonic development
D. A distortion of a normally formed structure due to mechanical forces

Answer 4

A. A group of anomalies with a single genetic or environmental cause

Rationale:

Malformation syndrome refers to a constellation of defects caused by a single genetic, chromosomal, or environmental factor.
Example: Down Syndrome (Trisomy 21) presents with intellectual disability, cardiac defects, and characteristic facial features—all due to the same chromosomal defect.
Sequence (B) involves one primary defect leading to secondary anomalies.
Malformation (C) is a single defect rather than a pattern.
Deformation (D) occurs due to external forces like uterine compression (not an intrinsic defect).

Question 5

A 2-month-old infant is brought in for evaluation due to developmental delay and distinct facial features, including upslanting palpebral fissures, a flat nasal bridge, and a single palmar crease. Echocardiography reveals an atrioventricular septal defect (AVSD). Karyotyping confirms the presence of an extra chromosome 21. What is the most appropriate classification of this condition?

A. Malformation/Anomaly
B. Malformation Sequence
C. Malformation Syndrome
D. Deformation

Answer 5

C. Malformation Syndrome

Rationale:

Down Syndrome (Trisomy 21) is a classic example of malformation syndrome, where multiple defects (craniofacial, cardiac, neurological) result from a single genetic cause (extra chromosome 21).
It is not an isolated malformation (A) because it involves multiple system abnormalities.
It is not a sequence (B) because defects arise independently rather than from a single primary defect.
It is not a deformation (D) since features are due to intrinsic genetic abnormalities, not mechanical forces.

Question 6

Which of the following is an example of a malformation syndrome rather than a sequence or isolated anomaly?

A. Cleft palate due to a teratogen
B. Myelomeningocele leading to clubfoot
C. VACTERL Association
D. Apert Syndrome (FGFR2 mutation)

Answer 6

D. Apert Syndrome (FGFR2 mutation)

Rationale:

Apert Syndrome is a malformation syndrome caused by a single gene mutation (FGFR2) and leads to craniosynostosis, syndactyly, and facial abnormalities.
Cleft palate (A) is an isolated malformation (not a syndrome).
Myelomeningocele + clubfoot (B) is a sequence (not a syndrome).
VACTERL (C) is an association, not a syndrome since it lacks a single unifying cause.

Question 7

A full-term newborn has craniosynostosis, midface hypoplasia, and symmetric syndactyly of the hands and feet. Genetic testing reveals a mutation in the FGFR2 gene. What is the most appropriate classification of this condition?

A. Malformation Syndrome
B. Malformation Sequence
C. Association
D. Disruption

Answer 7

A. Malformation Syndrome

Rationale:

Apert Syndrome is a malformation syndrome caused by a single gene mutation (FGFR2).
Syndactyly and craniosynostosis are features of the syndrome, not secondary defects from a primary anomaly (so it’s not a sequence).
It is not an association (C) because the anomalies are genetically linked.
It is not a disruption (D) because no external factors damaged normal tissue.

Question 8

A newborn boy is found to have vertebral anomalies, anal atresia, tracheoesophageal fistula, and renal anomalies. The neonatologist suspects VACTERL association. What distinguishes an association from other types of dysmorphism?

A. A group of anomalies occurring together more often than by chance, but without a single cause
B. A primary defect causing a cascade of secondary anomalies
C. An isolated structural defect due to abnormal embryonic development
D. A genetic syndrome with a specific chromosomal abnormality

Answer 8

A. A group of anomalies occurring together more often than by chance, but without a single cause

Rationale:

An association is a cluster of anomalies that occur together more often than expected by chance, but without a known genetic or environmental cause.
VACTERL Association includes:
V: Vertebral anomalies
A: Anal anomalies
C: Cardiac defects
TE: Tracheoesophageal fistula
R: Renal anomalies
L: Limb anomalies
Syndromes (D) have a single genetic cause, whereas associations do not.
Sequences (B) involve one primary defect triggering secondary anomalies.
Malformations (C) refer to a single congenital defect rather than a combination of findings.

Question 9

Which of the following is NOT part of the VACTERL Association?

A. Vertebral anomalies
B. Cleft lip and palate
C. Tracheoesophageal fistula
D. Renal anomalies

Answer 9

B. Cleft lip and palate

Rationale:

VACTERL Association includes vertebral, anal, cardiac, tracheoesophageal, renal, and limb anomalies.
Cleft lip and palate is associated with other syndromes, such as Pierre Robin Sequence or Trisomy 13/18 but not VACTERL.

Question 10

A 35-year-old primigravida presents for prenatal consultation. Ultrasound reveals a fetus with contractures of the limbs and talipes equinovarus (clubfoot). Further history reveals the pregnancy is complicated by severe oligohydramnios. Which of the following best describes this condition?

A. Malformation
B. Deformation
C. Disruption
D. Dysplasia

Answer 10

B. Deformation

Rationale:

Deformation occurs when a normally developing structure is physically altered due to external forces.
Oligohydramnios (low amniotic fluid) can compress the fetus, leading to limb contractures, clubfoot, and craniofacial abnormalities.
It is not a malformation (A) because the organs/tissues developed normally but were altered later.
It is not a disruption (C) because no tissue destruction occurred.
It is not dysplasia (D) since the defect is not due to cellular disorganization.

Question 11

Which of the following is the most common cause of deformations in utero?

A. Genetic mutations
B. Uterine malformations, twins, oligohydramnios
C. Teratogenic exposure in the first trimester
D. Defective organogenesis

Answer 11

B. Uterine malformations, twins, oligohydramnios

Rationale:

Deformations result from mechanical forces acting on a normally developing fetus.
Common causes:
Oligohydramnios (low amniotic fluid) → compression of the fetus
Twin pregnancy → restricted space leading to limb contractures
Uterine malformations → abnormal positioning of the fetus
Genetic mutations (A) and teratogens (C) cause malformations, not deformations.

Question 12

A newborn presents with amniotic band syndrome, causing congenital limb constrictions and digital amputations. The fetal ultrasound was normal initially, but later scans showed these abnormalities. What best describes the pathogenesis of this condition?

A. Malformation
B. Disruption
C. Deformation
D. Dysplasia

Answer 12

B. Disruption

Rationale:

Disruption occurs when previously normal tissue is destroyed due to external factors.
Amniotic bands can wrap around fetal limbs and cut off blood supply, leading to ischemia, necrosis, and limb amputation.
It is not a malformation (A) because the limbs were originally developing normally.
It is not deformation (C) since deformations do not involve tissue destruction.
It is not dysplasia (D) because dysplasia involves abnormal cellular organization.

Question 13

Which of the following is an example of a disruption rather than a malformation?

A. Achondroplasia
B. Amniotic band syndrome
C. Myelomeningocele
D. Pierre Robin Sequence

Answer 13

B. Amniotic band syndrome

Rationale:

Disruption = destruction of previously normal tissue.
Amniotic band syndrome → Fibrous bands cut off blood supply, leading to ring constrictions and amputations.
Achondroplasia (A) is a genetic dysplasia.
Myelomeningocele (C) is a malformation.
Pierre Robin Sequence (D) is a malformation sequence.

Question 14

A 5-year-old child presents with short stature, short limbs, and a large head with frontal bossing. Radiologic findings show loss of caudal widening in the vertebrae and short long bones of the lower limbs. What is the most likely diagnosis?

A. Marfan Syndrome
B. Achondroplasia
C. VACTERL Association
D. Amniotic Band Syndrome

Answer 14

B. Achondroplasia

Rationale:

Dysplasia is a defect in tissue organization at the cellular level.
Achondroplasia is caused by a mutation in FGFR3, leading to abnormal cartilage and bone growth.
Features:
Short stature
Large head with frontal bossing
Short limbs with trident hand appearance
It is not Marfan Syndrome (A) because Marfan presents with tall stature and cardiovascular problems.
It is not VACTERL (C) or Amniotic Band Syndrome (D) because those involve multiple unrelated anomalies or disruptions.

Question 15

Which of the following best defines dysplasia?

A. Abnormal cellular organization within tissue leading to structural changes
B. A primary defect causing a cascade of anomalies
C. A single congenital defect due to abnormal embryogenesis
D. A normal structure altered by external mechanical forces

Answer 15

A. Abnormal cellular organization within tissue leading to structural changes

Rationale:

Dysplasia results from abnormal cellular organization, leading to structural defects.
Example: Achondroplasia (defective cartilage growth).
Sequence (B) involves secondary defects, malformations (C) affect organogenesis, and deformations (D) are caused by external forces.

Question 16

A 3-year-old boy is brought to the clinic for short stature. On examination, he has a large head, frontal bossing, short limbs, and trident hands. His parents are of normal height. Radiographic findings reveal loss of caudal widening of vertebrae and short long bones. What is the most likely diagnosis?

A. Marfan Syndrome
B. Achondroplasia
C. Turner Syndrome
D. Down Syndrome

Answer 16

B. Achondroplasia

Rationale:

Achondroplasia is the most common cause of disproportionate short stature.
Features include macrocephaly, frontal bossing, short limbs, and trident hands.
It is not Marfan Syndrome (A) because Marfan presents with tall stature and cardiovascular issues.
Turner Syndrome (C) is associated with short stature, but with features like webbed neck and gonadal dysgenesis.
Down Syndrome (D) does not present with short limbs but rather intellectual disability and facial features like upslanting palpebral fissures.

Question 17

Which of the following syndromes is most commonly associated with tall stature?

A. Achondroplasia
B. Williams Syndrome
C. Marfan Syndrome
D. Turner Syndrome

Answer 17

C. Marfan Syndrome

Rationale:

Marfan Syndrome is characterized by tall stature, long limbs, arachnodactyly (long fingers), and cardiovascular abnormalities (aortic aneurysm, mitral valve prolapse).
Achondroplasia (A) causes short stature.
Williams Syndrome (B) does not affect stature significantly but is associated with cardiovascular defects and intellectual disability.
Turner Syndrome (D) causes short stature due to SHOX gene deletion.

Question 18

A 2-month-old infant presents with microcephaly, severe developmental delay, and holoprosencephaly on brain imaging. Physical exam reveals cleft lip and polydactyly. What is the most likely diagnosis?

A. Trisomy 21 (Down Syndrome)
B. Trisomy 13 (Patau Syndrome)
C. Trisomy 18 (Edwards Syndrome)
D. Williams Syndrome

Answer 18

B. Trisomy 13 (Patau Syndrome)

Rationale:

Trisomy 13 (Patau Syndrome) presents with:
Microcephaly
Severe developmental delay
Holoprosencephaly (failure of forebrain division)
Cleft lip/palate
Polydactyly
Down Syndrome (A) does not present with polydactyly or holoprosencephaly.
Trisomy 18 (C) causes clenched hands and rocker-bottom feet, not polydactyly.
Williams Syndrome (D) presents with hypertelorism and cardiovascular defects but not holoprosencephaly.

Question 19

Which of the following genetic conditions is most associated with hypertelorism (wide-set eyes)?

A. Williams Syndrome
B. Trisomy 18
C. Trisomy 21
D. Achondroplasia

Answer 19

A. Williams Syndrome

Rationale:

Williams Syndrome is associated with hypertelorism, elfin facies, and supravalvular aortic stenosis.
Trisomy 18 (B) presents with microcephaly and clenched fists.
Trisomy 21 (C) presents with upslanting palpebral fissures, not hypertelorism.
Achondroplasia (D) does not primarily affect eye spacing.

Question 20

A newborn is noted to have a single transverse palmar crease (Simian crease) on both hands. The baby also has hypotonia, upslanting palpebral fissures, and congenital heart disease. What is the most likely diagnosis?

A. Turner Syndrome
B. Down Syndrome
C. Noonan Syndrome
D. Klinefelter Syndrome

Answer 20

B. Down Syndrome

Rationale:

Down Syndrome (Trisomy 21) is characterized by:
Simian crease (single transverse palmar crease)
Hypotonia
Upslanting palpebral fissures
Congenital heart defects (endocardial cushion defects, AVSD)
Turner Syndrome (A) does not present with simian creases.
Noonan Syndrome (C) resembles Turner but occurs in both sexes and is linked to RASopathy.
Klinefelter Syndrome (D) is associated with infertility and tall stature but no palmar crease abnormalities.

Question 21

Which of the following genetic conditions is most associated with polydactyly?

A. Trisomy 21 (Down Syndrome)
B. Trisomy 18 (Edwards Syndrome)
C. Trisomy 13 (Patau Syndrome)
D. Turner Syndrome

Answer 21

C. Trisomy 13 (Patau Syndrome)

Rationale:

Trisomy 13 (Patau Syndrome) is the most common chromosomal condition associated with polydactyly.
Down Syndrome (A) is associated with Simian creases but not polydactyly.
Trisomy 18 (B) presents with clenched hands, not extra digits.
Turner Syndrome (D) does not affect digits.

Question 22

A 16-year-old boy presents to the clinic for a sports physical examination. He has a tall, thin build, long limbs, and hypermobile joints. On examination, he has long fingers (arachnodactyly), a high-arched palate, and pectus excavatum. Cardiac auscultation reveals a diastolic murmur, and echocardiography confirms aortic root dilation. What is the most likely diagnosis?

A. Marfan Syndrome
B. Ehlers-Danlos Syndrome
C. Homocystinuria
D. Klinefelter Syndrome

Answer 22

A. Marfan Syndrome

Rationale:

Marfan Syndrome is caused by an FBN1 (Fibrillin-1) mutation affecting connective tissue.
Features include:
Tall stature, long limbs (dolichostenomelia), and hypermobility
Aortic root dilation → risk of aortic aneurysm/dissection
Ectopia lentis (lens dislocation)
Pectus deformities (excavatum or carinatum)
Ehlers-Danlos Syndrome (B) also has hypermobility but lacks cardiac and eye findings.
Homocystinuria (C) mimics Marfan but presents with thrombosis, intellectual disability, and a downward lens dislocation.
Klinefelter Syndrome (D) causes tall stature but also includes hypogonadism and infertility.

Question 23

Which of the following is the most serious life-threatening complication of Marfan Syndrome?

A. Spontaneous pneumothorax
B. Aortic dissection
C. Lens dislocation
D. Mitral valve prolapse

Answer 23

B. Aortic dissection

Rationale:

The most serious complication of Marfan Syndrome is aortic dissection due to progressive aortic root dilation.
Lens dislocation (C) is characteristic but not life-threatening.
Mitral valve prolapse (D) is common but usually benign.
Spontaneous pneumothorax (A) can occur but is not the most critical complication.

Question 24

A 10-year-old boy presents with tall stature, long limbs, scoliosis, and pectus excavatum. His teacher reports intellectual disability and learning difficulties. He has a history of deep vein thrombosis (DVT) and a stroke at age 8. Ophthalmologic examination shows lens dislocation (ectopia lentis) downward. What is the most likely diagnosis?

A. Marfan Syndrome
B. Homocystinuria
C. Klinefelter Syndrome
D. Ehlers-Danlos Syndrome

Answer 24

B. Homocystinuria

Rationale:

Homocystinuria (CBS deficiency) presents with a Marfanoid habitus (tall, long limbs, scoliosis, pectus deformities) but differs by:
Intellectual disability
Thrombosis (DVT, stroke)
Lens dislocation downward (Marfan = upward)
Marfan Syndrome (A) has normal intelligence and no thrombosis.
Klinefelter Syndrome (C) has tall stature but features hypogonadism and infertility.
Ehlers-Danlos Syndrome (D) causes hypermobility but not thrombosis or intellectual disability.

Question 25

What is the best initial diagnostic test for Homocystinuria? A. Serum methionine levels B. Plasma homocysteine levels C. Urinary organic acid analysis D. Chromosomal karyotyping

Answer 25

B. Plasma homocysteine levels Rationale: Plasma homocysteine levels are the best initial test for homocystinuria (CBS deficiency). Serum methionine levels (A) may also be elevated but are not the primary test. Urinary organic acids (C) help diagnose metabolic disorders but not homocystinuria specifically. Karyotyping (D) detects chromosomal abnormalities, not metabolic defects.

Question 26

A 17-year-old male presents for evaluation due to learning difficulties and behavioral issues. He is taller than expected for his age, has mild speech delay, and has a history of aggressive outbursts and poor impulse control. Physical examination is unremarkable. Karyotyping reveals 47, XYY. What is the most likely diagnosis? A. Klinefelter Syndrome B. Turner Syndrome C. XYY Syndrome D. Fragile X Syndrome

Answer 26

C. XYY Syndrome Rationale: XYY Syndrome (47, XYY) is characterized by: Tall stature Learning disabilities and speech delay Behavioral issues (impulsivity, aggression, ADHD-like symptoms) Klinefelter Syndrome (A) (47, XXY) also causes tall stature but is associated with hypogonadism and infertility. Turner Syndrome (B) (45, X) is associated with short stature and primary amenorrhea. Fragile X Syndrome (D) presents with intellectual disability, large ears, and macroorchidism.

Question 27

Which of the following is most commonly seen in XYY Syndrome (47, XYY)? A. Hypogonadism and gynecomastia B. Tall stature and behavioral issues C. Short stature and congenital heart defects D. Intellectual disability with macroorchidism

Answer 27

B. Tall stature and behavioral issues Rationale: XYY Syndrome (47, XYY) presents with: Tall stature Behavioral problems (aggression, impulsivity, ADHD-like features) Mild learning difficulties Klinefelter Syndrome (A) causes hypogonadism and gynecomastia. Turner Syndrome (C) causes short stature and congenital heart defects. Fragile X Syndrome (D) causes intellectual disability and macroorchidism.

Question 28

A newborn male is brought in for evaluation due to poor feeding and hypotonia. Physical examination reveals upslanting palpebral fissures, epicanthal folds, a flat facial profile, and a single transverse palmar crease. What is the most likely diagnosis? 💡 A. Turner Syndrome 💡 B. Trisomy 21 💡 C. Trisomy 18 💡 D. Klinefelter Syndrome

Answer 28

B. Trisomy 21 📝 Rationale: Down syndrome is characterized by hypotonia, distinct craniofacial features, and a single palmar crease. Congenital heart defects (e.g., AV septal defect) are also common.

Question 29

A 3-day-old infant presents with micrognathia, low-set ears, and a prominent occiput. Physical examination reveals clenched fists with the index finger overlapping the third and the fifth overlapping the fourth finger. What is the likely diagnosis? 💡 A. Trisomy 13 💡 B. Trisomy 18 💡 C. Marfan Syndrome 💡 D. Turner Syndrome

Answer 29

B. Trisomy 18 📝 Rationale: Clenched fists with overlapping fingers are a classic feature of Edwards syndrome (Trisomy 18). Other features include rocker-bottom feet, congenital heart defects, and severe developmental delay.

Question 30

A neonate is born with severe microcephaly, cleft lip and palate, polydactyly, and an omphalocele. Echocardiography reveals a ventricular septal defect (VSD). What is the most likely chromosomal abnormality? 💡 A. Trisomy 21 💡 B. Trisomy 18 💡 C. Trisomy 13 💡 D. Turner Syndrome

Answer 30

C. Trisomy 13 📝 Rationale: Trisomy 13 (Patau syndrome) is associated with midline defects (cleft lip/palate, holoprosencephaly), polydactyly, and congenital heart defects.

Question 31

A 14-year-old girl presents with short stature, a webbed neck, and widely spaced nipples. She has not yet had menarche. On exam, she has normal intelligence but poor secondary sexual development. What is the most likely diagnosis? 💡 A. Klinefelter Syndrome 💡 B. Turner Syndrome 💡 C. Marfan Syndrome 💡 D. Trisomy 18

Answer 31

B. Turner Syndrome 📝 Rationale: Turner syndrome (45,X) presents with short stature, webbed neck, shield chest, and primary amenorrhea due to ovarian dysgenesis.

Question 32

A 17-year-old male presents with tall stature, small testes, and gynecomastia. He reports difficulty with reading and writing and mild learning disabilities. What is the most likely diagnosis? 💡 A. Klinefelter Syndrome 💡 B. Turner Syndrome 💡 C. Marfan Syndrome 💡 D. Fragile X Syndrome

Answer 32

A. Klinefelter Syndrome 📝 Rationale: Klinefelter syndrome (47,XXY) is characterized by tall stature, gynecomastia, small testes, and learning disabilities. It results from an extra X chromosome, leading to low testosterone and infertility.

Question 33

Which of the following chromosomal conditions is most commonly associated with a single palmar crease, congenital heart defects, and intellectual disability? 💡 A. Trisomy 21 💡 B. Trisomy 18 💡 C. Trisomy 13 💡 D. Turner Syndrome

Answer 33

A. Trisomy 21 📝 Rationale: Single palmar crease + hypotonia + congenital heart disease (AVSD) → Down syndrome (Trisomy 21).

Question 34

Which of the following is a distinguishing feature of Edwards Syndrome (Trisomy 18)? 💡 A. Polydactyly 💡 B. Clenched fists with overlapping fingers 💡 C. Single palmar crease 💡 D. Webbed neck

Answer 34

B. Clenched fists with overlapping fingers 📝 Rationale: Trisomy 18 (Edwards syndrome) is best recognized by clenched fists, rocker-bottom feet, and micrognathia.

Question 35

A 6-month-old infant presents with severe intellectual disability, inappropriate laughter, and ataxic gait. Genetic testing shows a deletion on maternal chromosome 15q11-13. What is the most likely diagnosis? 💡 A. Prader-Willi Syndrome 💡 B. Angelman Syndrome 💡 C. Beckwith-Wiedemann Syndrome 💡 D. Williams Syndrome

Answer 35

B. Angelman Syndrome 📝 Rationale: Angelman Syndrome is caused by maternal chromosome 15q11-13 deletion and presents with happy demeanor, ataxia, and severe intellectual disability.

Question 36

Which of the following is a common cardiac defect in Down Syndrome (Trisomy 21)? 💡 A. Tetralogy of Fallot 💡 B. Ventricular Septal Defect (VSD) 💡 C. Atrioventricular Septal Defect (AVSD) 💡 D. Pulmonary Stenosis

Answer 36

C. Atrioventricular Septal Defect (AVSD) 📝 Rationale: Down syndrome is highly associated with AVSD, a defect affecting both the atrial and ventricular septa due to abnormal endocardial cushion development.

Question 37

A 9-year-old boy presents with large ears, a long face, and intellectual disability. His teacher reports hyperactivity and social anxiety. His mother states that her brother had similar symptoms. What is the most likely diagnosis? 💡 A. Fragile X Syndrome 💡 B. Down Syndrome 💡 C. Klinefelter Syndrome 💡 D. Turner Syndrome

Answer 37

A. Fragile X Syndrome 📝 Rationale: Fragile X Syndrome is X-linked, causing intellectual disability, large ears, a long face, and hyperactivity.

Question 38

A 16-year-old male is seen in the clinic for delayed puberty. He is tall with long limbs, has small testes, and exhibits gynecomastia. His teacher reports he has mild learning difficulties. What is the most likely diagnosis? 💡 A. Turner Syndrome 💡 B. Klinefelter Syndrome 💡 C. Fragile X Syndrome 💡 D. Noonan Syndrome

Answer 38

B. Klinefelter Syndrome 📝 Rationale: Klinefelter syndrome (47,XXY) is the most common sex chromosome disorder in males. Key features include tall stature, small testes, gynecomastia, and mild learning disabilities due to testosterone deficiency.

Question 39

Which of the following statements is true regarding Klinefelter Syndrome? 💡 A. It is associated with a high risk of Wilms’ tumor 💡 B. It results from a 47,XYY karyotype 💡 C. It is caused by an extra X chromosome (47,XXY) 💡 D. It primarily affects females

Answer 39

C. It is caused by an extra X chromosome (47,XXY) 📝 Rationale: Klinefelter Syndrome results from an extra X chromosome (47,XXY), affecting males, leading to infertility, gynecomastia, and learning difficulties.

Question 40

A 2-year-old child presents with severe intellectual disability, frequent inappropriate laughter, ataxic gait, and seizures. Genetic testing reveals a deletion on the maternal chromosome 15q11-13. What is the most likely diagnosis? 💡 A. Prader-Willi Syndrome 💡 B. Angelman Syndrome 💡 C. Down Syndrome 💡 D. Williams Syndrome

Answer 40

B. Angelman Syndrome 📝 Rationale: Angelman Syndrome is caused by the deletion of the maternal chromosome 15q11-13. Classic features include severe intellectual disability, ataxia, frequent laughter, and seizures (nicknamed "Happy Puppet Syndrome").

Question 41

Which of the following is the key genetic mechanism in Angelman Syndrome? 💡 A. Paternal uniparental disomy of chromosome 15 💡 B. Maternal deletion of chromosome 15q11-13 💡 C. Trisomy 18 💡 D. X-linked inheritance

Answer 41

B. Maternal deletion of chromosome 15q11-13 📝 Rationale: Angelman Syndrome occurs when the maternal chromosome 15q11-13 is deleted, while Prader-Willi Syndrome occurs when the paternal chromosome 15q11-13 is deleted.

Question 42

A 5-year-old boy is brought to the clinic due to excessive eating, obesity, and hypotonia. His parents report delayed milestones and poor suck reflex as a newborn. Genetic testing reveals paternal deletion of chromosome 15q11-13. What is the most likely diagnosis? 💡 A. Angelman Syndrome 💡 B. Prader-Willi Syndrome 💡 C. Beckwith-Wiedemann Syndrome 💡 D. Klinefelter Syndrome

Answer 42

B. Prader-Willi Syndrome 📝 Rationale: Prader-Willi Syndrome results from the deletion of the paternal chromosome 15q11-13. Classic features include severe hypotonia at birth, hyperphagia, obesity, and intellectual disability.

Question 43

Which of the following is a hallmark neonatal finding in Prader-Willi Syndrome? 💡 A. Large mandible 💡 B. Polydactyly 💡 C. Hypotonia and weak suck reflex 💡 D. Short stature at birth

Answer 43

C. Hypotonia and weak suck reflex 📝 Rationale: Prader-Willi Syndrome is characterized by severe neonatal hypotonia and feeding difficulties, leading to poor weight gain initially, followed by hyperphagia and obesity in childhood.

Question 44

A newborn girl is noted to have macrosomia, macroglossia, and an umbilical hernia. An ultrasound is ordered due to the increased risk of Wilms’ tumor and hepatoblastoma. What is the most likely diagnosis? 💡 A. Prader-Willi Syndrome 💡 B. Angelman Syndrome 💡 C. Beckwith-Wiedemann Syndrome 💡 D. Turner Syndrome

Answer 44

C. Beckwith-Wiedemann Syndrome 📝 Rationale: Beckwith-Wiedemann Syndrome (BWS) is associated with macrosomia (large body size), macroglossia (large tongue), and an increased risk of Wilms' tumor and hepatoblastoma. It is linked to 11p15 imprinting defects.

Question 45

Which of the following is NOT a feature of Beckwith-Wiedemann Syndrome? 💡 A. Increased risk of Wilms’ tumor 💡 B. Macroglossia 💡 C. Short stature 💡 D. Omphalocele

Answer 45

C. Short stature 📝 Rationale: Beckwith-Wiedemann Syndrome is characterized by overgrowth (macrosomia), macroglossia, and increased risk of tumors. Short stature is NOT a feature; instead, affected individuals are large for gestational age.

Question 46

Which syndrome is most commonly associated with excessive eating and obesity in childhood? 💡 A. Prader-Willi Syndrome 💡 B. Angelman Syndrome 💡 C. Klinefelter Syndrome 💡 D. Down Syndrome

Answer 46

A. Prader-Willi Syndrome 📝 Rationale: Prader-Willi Syndrome is characterized by hyperphagia, obesity, and hypotonia.

Question 47

Which condition is best known as "Happy Puppet Syndrome" due to frequent laughter, ataxia, and intellectual disability? 💡 A. Prader-Willi Syndrome 💡 B. Angelman Syndrome 💡 C. Beckwith-Wiedemann Syndrome 💡 D. Williams Syndrome

Answer 47

B. Angelman Syndrome 📝 Rationale: Angelman Syndrome presents with ataxia, severe intellectual disability, and frequent laughter, leading to the nickname "Happy Puppet Syndrome."

Question 48

A 15-year-old male presents with tall stature, long fingers (arachnodactyly), hypermobile joints, and a high-arched palate. Auscultation reveals a mid-systolic click. Which of the following cardiovascular complications is this patient most at risk for? 💡 A. Aortic aneurysm and dissection 💡 B. Coarctation of the aorta 💡 C. Mitral valve stenosis 💡 D. Tricuspid atresia

Answer 48

A. Aortic aneurysm and dissection 📝 Rationale: Marfan Syndrome is caused by a mutation in the fibrillin gene, affecting connective tissue. Cardiovascular complications include aortic root dilation, leading to aortic aneurysm, dissection, and mitral valve prolapse (mid-systolic click).

Question 49

A 10-year-old girl presents with joint hypermobility, fragile skin, and poor wound healing. On examination, her skin is soft, stretchy, and bruises easily. Which of the following is the most likely diagnosis? 💡 A. Marfan Syndrome 💡 B. Ehlers-Danlos Syndrome 💡 C. Osteogenesis Imperfecta 💡 D. Klinefelter Syndrome

Answer 49

B. Ehlers-Danlos Syndrome 📝 Rationale: Ehlers-Danlos Syndrome (EDS) is a collagen disorder characterized by hyperextensible skin, joint hypermobility, and easy bruising. Severe forms may involve vascular complications (arterial rupture).

Question 50

A 6-month-old infant presents with failure to thrive, chronic cough, and greasy stools. A sweat chloride test confirms the diagnosis. What is the most common respiratory pathogen in children with this condition? 💡 A. Streptococcus pneumoniae 💡 B. Pseudomonas aeruginosa 💡 C. Mycoplasma pneumoniae 💡 D. Klebsiella pneumoniae

Answer 50

B. Pseudomonas aeruginosa 📝 Rationale: Cystic Fibrosis (CF) is caused by a mutation in the CFTR gene, leading to thick, sticky mucus in the lungs and pancreas. Pseudomonas aeruginosa is the most common and severe pathogen in CF patients.

Question 51

Which of the following is a hallmark gastrointestinal manifestation of Cystic Fibrosis? 💡 A. Meconium ileus 💡 B. Pyloric stenosis 💡 C. Hirschsprung disease 💡 D. Malrotation with volvulus

Answer 51

A. Meconium ileus 📝 Rationale: Meconium ileus (intestinal obstruction in newborns) is often the first sign of CF. Other GI complications include pancreatic insufficiency, fat malabsorption, and failure to thrive.

Question 52

A 7-year-old African-American boy presents with recurrent episodes of severe pain in his arms and legs. He has a history of splenic infarctions and dactylitis. A peripheral blood smear shows sickled red blood cells. What is the pathophysiology behind his pain? 💡 A. Autoimmune hemolysis 💡 B. Ischemia due to vaso-occlusion 💡 C. Vitamin B12 deficiency 💡 D. Thrombocytopenia

Answer 52

B. Ischemia due to vaso-occlusion 📝 Rationale: Sickle Cell Disease (SCD) is caused by a missense mutation in the β-globin gene, leading to sickled RBCs that block capillaries, causing ischemic pain (vaso-occlusive crisis).

Question 53

Which of the following conditions provides protection against malaria? 💡 A. Cystic Fibrosis 💡 B. Sickle Cell Trait 💡 C. Ehlers-Danlos Syndrome 💡 D. Turner Syndrome

Answer 53

B. Sickle Cell Trait 📝 Rationale: Individuals with Sickle Cell Trait (heterozygous HbAS) have partial protection against malaria caused by Plasmodium falciparum due to increased RBC turnover.

Question 54

A 5-year-old boy presents with spontaneous bruising and prolonged bleeding after a minor cut. He has a history of hemarthrosis (joint bleeds). Laboratory tests show a prolonged PTT with a normal PT and platelet count. What is the most likely diagnosis? 💡 A. Von Willebrand Disease 💡 B. Hemophilia A 💡 C. Hemophilia B 💡 D. Glanzmann Thrombasthenia

Answer 54

B. Hemophilia A 📝 Rationale: Hemophilia A (Factor VIII deficiency) and Hemophilia B (Factor IX deficiency) present with prolonged PTT, hemarthrosis, and easy bruising. Hemophilia A is more common than Hemophilia B.

Question 55

Which of the following is true regarding the genetics of Hemophilia? 💡 A. Autosomal dominant 💡 B. Autosomal recessive 💡 C. X-linked recessive 💡 D. X-linked dominant

Answer 55

C. X-linked recessive 📝 Rationale: Hemophilia A and B are X-linked recessive disorders, meaning they primarily affect males, while females are usually carriers.

Question 56

A 17-year-old male presents with tall stature, long fingers (arachnodactyly), hypermobile joints, and a history of sudden chest pain. His family history is significant for aortic dissections. What is the most likely pattern of inheritance? 💡 A. Autosomal Dominant (AD) 💡 B. Autosomal Recessive (AR) 💡 C. X-Linked Recessive (XLR) 💡 D. Mitochondrial

Answer 56

A. Autosomal Dominant (AD) 📝 Rationale: Marfan Syndrome, a disorder of connective tissue caused by fibrillin gene mutation, follows an autosomal dominant inheritance pattern. It is seen in every generation and affects both males and females.

Question 57

Which of the following inherited disorders follows an autosomal dominant pattern? 💡 A. Marfan Syndrome 💡 B. Cystic Fibrosis 💡 C. Sickle Cell Disease 💡 D. Duchenne Muscular Dystrophy

Answer 57

A. Marfan Syndrome 📝 Rationale: Autosomal Dominant disorders include Marfan Syndrome, Neurofibromatosis Type 1 (NF1), and Familial Hypercholesterolemia. Cystic Fibrosis and Sickle Cell Disease are autosomal recessive, while Duchenne MD is X-linked recessive.

Question 58

A 3-year-old child presents with failure to thrive, frequent lung infections, and greasy stools. Both parents are healthy, but they have a distant relative with a similar condition. What is the most likely inheritance pattern? 💡 A. Autosomal Dominant (AD) 💡 B. Autosomal Recessive (AR) 💡 C. X-Linked Recessive (XLR) 💡 D. Mitochondrial

Answer 58

B. Autosomal Recessive (AR) 📝 Rationale: Cystic Fibrosis (CF) is an autosomal recessive disorder, meaning both parents are carriers but unaffected. AR disorders appear in siblings but not in parents.

Question 59

A 4-year-old boy presents with easy bruising and prolonged bleeding after minor injuries. His maternal uncle had similar symptoms. Lab tests reveal prolonged PTT with normal platelet count and PT. What is the likely inheritance pattern of his condition? 💡 A. Autosomal Dominant (AD) 💡 B. Autosomal Recessive (AR) 💡 C. X-Linked Recessive (XLR) 💡 D. Mitochondrial

Answer 59

C. X-Linked Recessive (XLR) 📝 Rationale: Hemophilia A and B are X-linked recessive disorders. Males inherit the disease from their carrier mothers, and affected males cannot pass it to their sons. Maternal uncles often have the same condition.

Question 60

Which of the following diseases follows an X-linked recessive inheritance pattern? 💡 A. Cystic Fibrosis 💡 B. Marfan Syndrome 💡 C. Duchenne Muscular Dystrophy 💡 D. Familial Hypercholesterolemia

Answer 60

C. Duchenne Muscular Dystrophy 📝 Rationale: X-Linked Recessive disorders affect males and are inherited from carrier mothers. Examples include Duchenne Muscular Dystrophy, Hemophilia, and G6PD Deficiency.