USMLE Step 1
Practice question #6
A 5-year-old girl is brought to her pediatrician because her mother says she is frequently bumping into stationary objects while playing. Visual field examination shows bilateral peripheral vision defects. CT of the head reveals
calcifications in the pituitary fossa. Which of the following is the most likely origin of this child's brain tumor?
A) Adenohypophyseal lactotrophs
B) Fourth ventricle neuroectoderm
C) Rathke's pouch
D) Vascular endothelium
E) Ventricular lining
Explanation: The visual field defect described is a bitemporal hemianopia, typically caused by lesions in the sella turcica impinging on the optic chiasm. In children the most common tumor in this location is a craniopharyngioma, derived from the remnants of Rathke's pouch.
This embryologic structure buds from the roof of the mouth to form the anterior pituitary. Bitemporal hemianopia is typically accompanied by severe headaches and poor pituitary function. Treatment includes surgery, radiotherapy, or both. 📝The correct answer is C.
#embryology
💥💥💥💥💥💥💥💥💥💥💥💥
Usmle Practice question #7
A baby boy dies 2 days after birth. He was born with wrinkled skin, deformed limbs, and abnormal facies. The mother's pregnancy was complicated by oligohydramnios. Which of the following embryologic process most likely failed in this child?
A) Development of dermis
B) Development of the kidneys
C) Fusion of maxillary and medial nasal prominences
D) Migration of neural crest cells to the distal colon
E) Outgrowth of limb buds
#embryology
Source: First Aid. Embryology
The correct answer is B. The presentation described here is consistent with Potter's syndrome, or bilateral renal agenesis. The failure of both kidneys to develop leads to oligohydramnios because the fetus cannot excrete urine into the amniotic sac. This in turn allows compression of the fetus by the uterine wall, leading to limb deformities, abnormal facies, and wrinkly skin. Death occurs shortly after birth unless an appropriate donor is found.
Answer A is incorrect. A failure of development of the dermis would not present with oligohydramnios or deformed limbs, but rather skin abnormalities.
Answer C is incorrect. This describes the etiology of cleft lip, which doesn't cause oligohydramnios or wrinkly skin and is compatible with life.
Answer D is incorrect. This describes the defect in Hirschsprung's disease, which results in failure to pass meconium and in constipation, but doesn't share any of the symptoms in this scenario.
Answer E is incorrect. A problem with limb bud growth would not produce abnormal facies or oligohydramnios.
💭💭💭💭💭💭💭💭💭💭💭💭💭
Usmle Practice question #8
A neonate is found to have strong, bounding pulses in both upper extremities and carotids, but her femoral pulses are very weak. She is diagnosed with coarctation of the aorta and is taken to surgery to correct the defect. Subsequent follow-up examinations show no further heart abnormalities. Sixteen years later, the patiet is noted to have poorly developed sexondary sexual characteristics, including persistent, nonprogressive Tanner stage 2 breast and pubic hair development. She has not experienced menarche. Which of the following would most likely be found in this patient?
A) Decreased estrogen levels
B) Normal ovaries
C) Patent ductus arteriosus
D) Simian crease
E) 46, XY karyotype
#embryology
Source: First Aid. Embryology
Explanation: The patient has Turner's syndrome, which is associated with coarctation of the aorta. Turner's syndrome often presents in adolescence with amenorrhea, and a diagnostic work-up shows a 45, XO karyotype. Patients with Turner's syndrome have poor development of secondary sexual characteristics and are infertile. So the correct answer is A. Those patients have rudimentary ovaries and that is why the answer B is incorrect.
Answer C is incorrect, because Turner's syndrome is not associated with PDA. Also, in the vignette the patient's cardiac examination is normal. With a PDA, the patient would have a continuous machinelike murmur.
Answer D is incorrect, because a simian crease is seen in Down's syndrome (trisomy 21), but not in Turner's syndrome. Answer E is incorrect, because patients with Turner's syndrome have a 45, XO karyotype.
🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯🗯
Usmle Practice question #9
Immediately following delivery, a newborn is observed to have multiple abnormalities, including a small lower jaw, abnormal feet, and that are clenched into fists. Despite supportive therapy for a congenital heart condition, the baby dies before 1 year of age. What is the likely etiology of the patient's condition?
A) CAG tandem repeats
B) Deletion of chromosome 21
C) Trisomy of chromosome 13
D) Trisomy of chromosome 18
E) X chromosome fragility
#embryology #FirstAid
Explanation: This newborn has Edwards' syndrome, or trisomy 18 (answer D). Affected children are born with clenched fists, rocker-bottom feet, micrognathia (a small lower jaw), congenital heart disease, and mental retardation. The survival rate of less than 1 year is similar to that of trisomy 13 (Patau's syndrome), from which it should be distinguished.
Answer A is incorrect. CAG tandem repeats are found in Huntington's disease, among others. Huntington's disease is characterized by degeneration of the caudate and putamen, leading to choreiform (dancelike) movements, but not the birth defects found in this patient.
Answer B is incorrect. A deletion of chromosome 21 may cause physical deformity, but clenched fists and rocker-bottom feet are classic for trisomy 18.
Answer C is incorrect. Trisomy of chromosome 13, or Patau's syndrome, is characterized by a constellation of findings including mental retardation, microphthalmia, microcephaly cleft lip/palate, abnormal forebrain structures polydactyly, and congenital heart disease.
Answer E is incorrect. This is fragile X syndrome. Associated with CGG tandem repeats, this syndrome is characterized by mental retardation, a large jaw, and large testes. Children with fragile X syndrome typically survive beyond 1 year of age.
💜💜💜💜💜💜💜💜💜💜💜💜💜💜
Usmle Practice question #10
An 11-year-old girl is brought to the pediatrician with complaints of back pain. On physical examination, a right thoracic scoliotic curve is noted. An x-ray film indicates that the curve is 25 degrees. Girls with scoliosis need to be especially carefully watched during peak height velocity, during which the curvature can dramatically worsen. Given that peak height velocity occurs during a particular Tanner stage, what other physical attributes would one expect to occur in the girl at the same time?
(A) Elevation of the breast papilla only and no pubic hair
(B) Enlargement of the breast and areola with a single contour and darker, coarse curled pubic hair
(C) Mature breast adult quantity and pattern of pubic hair that extends to the thighs
(D) Projection of the areola and papilla with separate contours and adult-type pubic hair limited to the genital area
(E) Small breast buds with elevation of breast and papilla and sparse, straight, downy hair on the labial base
Source: First Aid Q&A 2nd ed. #behavioralscience
Explanation: The correct answer is B. Tanner stage 3 is the stage when most girls experience peak height velocity. Peak height velocity occurs approximately 1 year after the initiation of breast development.
Answer A is incorrect. This description corresponds to Tanner stage 1.
Answer C is incorrect. This description corresponds to Tanner stage 5.
Answer D is incorrect. This description corresponds to Tanner stage 4.
Answer E is incorrect. This description corresponds to Tanner stage 2.
💝💝💝💝💝💝💝💝💝💝💝💝💝
Hope you like it .
#HappyLearning 💟
Get email subscription and follow us on blogs 💥
Also please subscribe us on youtube .link is given below
