An 18-month-old boy, whose parents are first cousins, is referred to you because of a significant episode of epistaxis. The parents report that the child had bleeding after circumcision and large hematomas with immunizations. Platelet aggregation studies show the following: This child's platelets are unable to interact with which of the following?

Correct Answer: B

Rationale: The correct answer is B: Fibrinogen. In this case, the child is likely suffering from Glanzmann thrombasthenia, a rare inherited platelet disorder where platelets lack the ability to bind to fibrinogen. This results in impaired platelet aggregation and clot formation, leading to bleeding tendencies. The other options (A, C, D) are not affected in Glanzmann thrombasthenia. Platelets interact normally with ADP (A), von Willebrand factor (C), and Platelet factor 4 (D) in this disorder.

Correct Answer: D

Rationale: Step 1: The patient's pain is described as burning, tingling, and shooting in her left leg, which suggests neuropathic pain. Step 2: The pain worsens with hot showers, indicating sensitivity to temperature changes, a common feature of neuropathic pain. Step 3: Gabapentin is a first-line medication for neuropathic pain, as it stabilizes nerve cells and reduces abnormal pain signaling. Step 4: Starting low and titrating upward on gabapentin dose helps minimize side effects and optimize pain relief. Step 5: Methadone (Choice A) is not the best option for neuropathic pain. Increasing immediate release oxycodone (Choice B) may lead to opioid tolerance. Amitriptyline (Choice C) may help neuropathic pain but is not as specific as gabapentin.

Correct Answer: A

Rationale: The correct answer is A: Abnormal lysosomal biogenesis. In this case, the clinical presentation of silvery hair and hypopigmented skin suggests a diagnosis of Chediak-Higashi syndrome, a rare autosomal recessive disorder affecting lysosomal function. The abnormal leukocyte count and neutrophil percentage indicate impaired immune function due to defective lysosomal biogenesis. The other choices, B: Abnormal ribosome function, C: Abnormal phagocytosis of opsonized particles, and D: Abnormal mitochondrial activity, do not align with the clinical presentation and laboratory findings of this specific case.

Correct Answer: A

Rationale: The correct answer is A. A semen analysis at this point would provide accurate information about future fertility because it assesses sperm count, motility, and morphology, which are crucial indicators of fertility potential. This is important for the patient to understand his current fertility status and make informed decisions about future fertility preservation options. Choice B is incorrect because males are also susceptible to gonadal toxicity from alkylating agents, and there is no evidence to suggest that they can maintain gonadal function at higher dosages compared to females. Choice C is incorrect because sperm cryopreservation should ideally have been offered at the time of leukemia diagnosis, but it is not too late to assess current fertility status with a semen analysis. Choice D is incorrect as the patient's primary concern is infertility, not testosterone deficiency, which is a different issue altogether.

Correct Answer: C

Rationale: The correct answer is C: The mean is greater than the median and mode. In a highly right-skewed distribution, the mean is pulled towards the higher end by the extreme values, making it greater than the median, which is the middle value. The mode is the most frequent value, which is typically lower than the mean in a right-skewed distribution. In summary, the mean is influenced by extreme values, causing it to be greater than both the median and the mode in a highly right-skewed distribution.