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Infection, Pharmacology & VTE MCQs

Practice Set 67 of 68

This practice set contains high-yield board review questions covering key concepts in Infection, Pharmacology & VTE. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1321

Topic: Infection, Pharmacology & VTE

A patient with an acute gout flare is evaluated in the emergency department. He has a history of severe chronic kidney disease (Stage IV). Which of the following is the most appropriate initial treatment for his acute flare?

. Indomethacin
. Allopurinol
. Intra-articular or systemic corticosteroids
. High-dose colchicine
. Probenecid

Correct Answer & Explanation

. Intra-articular or systemic corticosteroids

Explanation

In patients with severe chronic kidney disease, NSAIDs and colchicine are generally contraindicated due to toxicity risks. Corticosteroids (intra-articular or systemic) are the safest and most effective option for acute flares in this population.

Question 1322

Topic: Infection, Pharmacology & VTE

A 4-year-old boy presents with a sudden onset limp and refuses to bear weight on his right leg. He has a temperature of 38.8 C. Labs show an ESR of 45 mm/h and a WBC count of 13,500/mm3. According to the Kocher criteria, what is the probability that he has septic arthritis of the hip?

. 40%
. 71%
. 93%
. 99%
. 100%

Correct Answer & Explanation

. 99%

Explanation

The Kocher criteria for pediatric septic hip include: non-weight-bearing, temperature >38.5 C, ESR >40 mm/h, and WBC >12,000/mm3. The presence of all 4 criteria yields a 99% predicted probability of septic arthritis.

Question 1323

Topic: Infection, Pharmacology & VTE

A 3-week-old neonate in the NICU develops swelling of the left thigh and pseudoparalysis of the left leg. The hip is held in flexion, abduction, and external rotation.

What is the most common causative organism for this condition in this age group?

. Streptococcus pyogenes
. Neisseria gonorrhoeae
. Staphylococcus aureus
. Kingella kingae
. Haemophilus influenzae

Correct Answer & Explanation

. Staphylococcus aureus

Explanation

Staphylococcus aureus is the most common cause of pediatric septic arthritis across all age groups, including neonates. Group B Streptococcus and Gram-negative bacilli are also important pathogens in the neonatal period.

Question 1324

Topic: Infection, Pharmacology & VTE

A 6-year-old child presents with atraumatic hip pain and fever. An ultrasound is performed, which reveals an asymmetry in the anterior capsular distance of 3 mm compared to the contralateral hip. Which of the following is the most appropriate next step to confirm the diagnosis?

. Immediate empiric intravenous antibiotics
. Ultrasound-guided hip aspiration
. MRI of the pelvis without contrast
. Bone scintigraphy
. Observation and repeat ultrasound in 48 hours

Correct Answer & Explanation

. Ultrasound-guided hip aspiration

Explanation

An anterior capsular distance asymmetry of >2 mm on ultrasound indicates a significant hip effusion. Ultrasound-guided aspiration is the definitive diagnostic step to differentiate septic arthritis from transient synovitis via cell count, Gram stain, and culture.

Question 1325

Topic: Infection, Pharmacology & VTE

A 50-year-old man presents with an acute flare of gout in his knee. He is prescribed colchicine. What is the mechanism of action of this medication in the treatment of acute gout?

. Inhibits xanthine oxidase
. Increases renal excretion of uric acid
. Inhibits microtubule polymerization
. Blocks interleukin-1 (IL-1) receptors
. Inhibits cyclooxygenase-2 (COX-2) selectively

Correct Answer & Explanation

. Inhibits microtubule polymerization

Explanation

Colchicine works by binding to tubulin and inhibiting microtubule polymerization. This impairs neutrophil chemotaxis and degranulation, effectively reducing the acute inflammatory response to monosodium urate crystals.

Question 1326

Topic: Infection, Pharmacology & VTE
A 4-year-old boy presents with a limp, a temperature of 38.8°C, and refusal to bear weight on his right leg. Lab work shows a WBC of 13,000/mm³ and an ESR of 55 mm/hr. Which of the following represents the most appropriate next step in management?
. Observation and oral NSAIDs
. MRI of the pelvis without contrast
. Ultrasound-guided aspiration of the right hip
. CT scan of the bilateral hips
. Immediate open reduction and internal fixation

Correct Answer & Explanation

. Ultrasound-guided aspiration of the right hip

Explanation

The patient meets all four Kocher criteria (non-weight-bearing, fever >38.5°C, ESR >40 mm/hr, WBC >12,000/mm³), indicating a 99% probability of septic arthritis. Ultrasound-guided aspiration is the most appropriate next step for definitive diagnosis before surgical washout.

Question 1327

Topic: Infection, Pharmacology & VTE

A 60-year-old man with a history of severe peptic ulcer disease and chronic kidney disease (eGFR 25 mL/min) presents with an acute gout flare in his left knee. Which of the following is the most appropriate initial pharmacological treatment for this acute flare?

. Indomethacin
. Allopurinol
. Intra-articular corticosteroid injection
. Probenecid
. Intravenous colchicine

Correct Answer & Explanation

. Intra-articular corticosteroid injection

Explanation

NSAIDs are contraindicated in patients with severe peptic ulcer disease and poor renal function. Intra-articular corticosteroids are the safest and most effective option for managing an acute monoarticular gout flare in this specific patient.

Question 1328

Topic: Infection, Pharmacology & VTE

A 3-week-old infant in the NICU develops an acutely swollen and erythematous right hip. Aspiration of the joint reveals purulent fluid. While Staphylococcus aureus is the most common pathogen overall, which of the following organisms is particularly unique to this age group and must be covered empirically?

. Neisseria gonorrhoeae
. Kingella kingae
. Group B Streptococcus
. Salmonella typhi
. Pseudomonas aeruginosa

Correct Answer & Explanation

. Group B Streptococcus

Explanation

In neonates (age < 1 month), Group B Streptococcus (S. agalactiae) and Gram-negative bacilli are common causes of septic arthritis, in addition to S. aureus. Empirical antibiotic coverage must include agents effective against these organisms.

Question 1329

Topic: Infection, Pharmacology & VTE

A 3-year-old child presents with a limp, refusal to bear weight, a temperature of 38.8 C, an ESR of 45 mm/hr, and a peripheral WBC of 13,000/mm^3. According to the Kocher criteria, what is the probability that this child has septic arthritis of the hip?

. 3%
. 40%
. 71%
. 93%
. 99%

Correct Answer & Explanation

. 99%

Explanation

The Kocher criteria include non-weight-bearing, temperature > 38.5 C, ESR > 40 mm/hr, and WBC > 12,000/mm^3. The presence of all four criteria yields a 99% predictive probability for septic arthritis of the hip.

Question 1330

Topic: Infection, Pharmacology & VTE

Septic arthritis of the hip in infants is frequently complicated by concurrent osteomyelitis of the proximal femur. What anatomical feature of the infant hip uniquely predisposes to this rapid contiguous spread?

. Absence of the ligamentum teres
. Intra-articular position of the femoral neck metaphysis
. Hypervascularity of the greater trochanter
. Direct connection of the hip capsule to the bladder
. Avascular nature of the infant labrum

Correct Answer & Explanation

. Intra-articular position of the femoral neck metaphysis

Explanation

In infants, the metaphysis of the proximal femur lies entirely within the joint capsule. Consequently, hematogenous metaphyseal osteomyelitis can easily rupture through the thin cortex directly into the joint, resulting in septic arthritis.

Question 1331

Topic: Infection, Pharmacology & VTE

A 2-week-old premature infant in the neonatal intensive care unit develops an acutely swollen left thigh and holds the hip in a flexed and externally rotated position. In addition to Staphylococcus aureus, which organism is a leading cause of septic coxitis in this age group and requires empirical coverage?

. Neisseria gonorrhoeae
. Haemophilus influenzae type B
. Group B Streptococcus
. Salmonella enteritidis
. Borrelia burgdorferi

Correct Answer & Explanation

. Group B Streptococcus

Explanation

In neonates (infants less than 4 weeks old), the most common causative organisms for septic arthritis are Staphylococcus aureus, Group B Streptococcus, and Gram-negative bacilli. Empiric antibiotic therapy must broadly cover these pathogens.

Question 1332

Topic: Infection, Pharmacology & VTE

Acute hematogenous osteomyelitis in children most commonly localizes to the metaphysis of long bones. Which of the following anatomical features of the pediatric metaphysis is the primary reason for this specific localization?

. High concentration of phagocytic cells in the metaphyseal marrow
. Presence of sluggish, turbulent blood flow in terminal venous sinusoids
. Direct arterial anastomoses between the metaphysis and epiphysis
. Lack of a periosteal layer covering the metaphyseal cortex
. High oxygen tension favoring aerobic bacterial proliferation

Correct Answer & Explanation

. Presence of sluggish, turbulent blood flow in terminal venous sinusoids

Explanation

Correct Answer: BIn children, the metaphysis is the most common site for acute hematogenous osteomyelitis. The nutrient artery branches into small arterioles that form sharp, hairpin loops at the physeal border before emptying into large venous sinusoids. This anatomical arrangement causes sluggish, turbulent blood flow, which allows blood-borne bacteria to settle and proliferate in an area with relatively low local phagocytic activity.

Question 1333

Topic: Infection, Pharmacology & VTE

A 62-year-old diabetic patient presents with a chronic plantar ulcer under the first metatarsal head. Which of the following clinical findings or tests has the highest positive predictive value for diagnosing underlying osteomyelitis in this specific setting?

. Erythrocyte sedimentation rate > 40 mm/hr
. Positive probe-to-bone test
. Plain radiography showing soft tissue swelling
. C-reactive protein > 10 mg/L
. Presence of purulent drainage

Correct Answer & Explanation

. Positive probe-to-bone test

Explanation

A positive probe-to-bone test (palpating hard, gritty bone with a sterile blunt probe through an ulcer) has a remarkably high positive predictive value (approaching 90%) for underlying osteomyelitis in diabetic foot infections.

Question 1334

Topic: Infection, Pharmacology & VTE

A 12-year-old child with an autosomal dominant form of osteopetrosis complains of severe jaw pain and swelling after a dental extraction. Given the underlying bone pathology, what is the most likely complication?

. Pathologic fracture of the mandible
. Mandibular osteomyelitis
. Secondary ameloblastoma
. Avascular necrosis of the TMJ
. Rapid malignant transformation

Correct Answer & Explanation

. Mandibular osteomyelitis

Explanation

Patients with osteopetrosis are highly susceptible to osteomyelitis, particularly of the mandible following dental procedures. The extremely dense, avascular nature of the osteopetrotic bone prevents adequate immune response and antibiotic penetration.

Question 1335

Topic: Infection, Pharmacology & VTE

During a primary total knee arthroplasty in a patient with a severe, unyielding 20-degree varus deformity, what is the widely accepted standard sequence for sequential medial soft tissue release?

. Deep MCL, posteromedial capsule, superficial MCL, pes anserinus.
. Superficial MCL, pes anserinus, deep MCL.
. Deep MCL, semimembranosus, superficial MCL, pes anserinus.
. Posteromedial capsule, pes anserinus, deep MCL.
. Pes anserinus, deep MCL, superficial MCL.

Correct Answer & Explanation

. Deep MCL, posteromedial capsule, superficial MCL, pes anserinus.

Explanation

The standard sequence for a medial soft tissue release in a varus TKA begins with the deep MCL. This is followed sequentially by the posteromedial capsule (and semimembranosus), the superficial MCL (periosteal sleeve release), and finally the pes anserinus if severe contracture persists.

Question 1336

Topic: Infection, Pharmacology & VTE

During a Total Knee Arthroplasty in a patient with a severe fixed varus deformity, what is the standard sequential soft tissue release performed on the medial side?

. Superficial MCL, Deep MCL, Pes Anserinus
. Deep MCL, Posteromedial capsule, Semimembranosus, Superficial MCL
. Pes Anserinus, Semimembranosus, Deep MCL
. Posteromedial capsule, Superficial MCL, PCL
. Superficial MCL, ACL, PCL, Semimembranosus

Correct Answer & Explanation

. Deep MCL, Posteromedial capsule, Semimembranosus, Superficial MCL

Explanation

The classic sequential medial release for a fixed varus knee begins with osteophyte excision, followed by the deep MCL, posteromedial capsule, semimembranosus insertion, and finally the superficial MCL if further correction is needed.

Question 1337

Topic: Infection, Pharmacology & VTE

A newborn is noted to have short proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and the spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic disorder?

. Valproic acid
. Warfarin
. Lithium
. Thalidomide
. Phenytoin

Correct Answer & Explanation

. Warfarin

Explanation

Correct Answer: B (Warfarin)The clinical picture describes Chondrodysplasia Punctata (characterized by stippled epiphyses). Fetal warfarin syndrome (warfarin embryopathy) can produce a phenocopy of this condition, presenting with nasal hypoplasia and stippled epiphyses. Warfarin inhibits vitamin K-dependent proteins (like osteocalcin and matrix Gla protein) which are essential for normal bone and cartilage development.

Question 1338

Topic: Infection, Pharmacology & VTE

A neonate presents with severe shortening of the proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic skeletal dysplasia?

. Valproic acid
. Warfarin
. Lithium
. Thalidomide
. Alcohol

Correct Answer & Explanation

. Warfarin

Explanation

Correct Answer: WarfarinThe neonate's presentation is consistent with Chondrodysplasia Punctata (stippled epiphyses). Fetal warfarin syndrome (warfarin embryopathy) can cause a phenocopy of this condition, presenting with nasal hypoplasia, stippled epiphyses, and limb hypoplasia. Warfarin inhibits vitamin K-dependent proteins, including osteocalcin and matrix Gla protein, which are essential for normal bone and cartilage development.

Question 1339

Topic: Infection, Pharmacology & VTE

A newborn is noted to have short proximal limbs, cataracts, and ichthyosis. Radiographs reveal multiple punctate calcifications in the epiphyses of the long bones and the cartilaginous portions of the spine. Which of the following maternal exposures during pregnancy can produce a phenocopy of this genetic skeletal dysplasia?

. Phenytoin
. Warfarin
. Valproic acid
. Lithium
. Thalidomide

Correct Answer & Explanation

. Warfarin

Explanation

Correct Answer: BThe clinical and radiographic description is classic for Chondrodysplasia Punctata (stippled epiphyses). Maternal use of Warfarin during pregnancy (fetal warfarin syndrome or warfarin embryopathy) can cause a phenocopy of this genetic disorder. Warfarin inhibits vitamin K-dependent proteins, including osteocalcin and matrix Gla protein, leading to abnormal bone and cartilage calcification, resulting in stippled epiphyses, nasal hypoplasia, and short limbs. Thalidomide (Option E) causes phocomelia, not stippled epiphyses.

Question 1340

Topic: Infection, Pharmacology & VTE

A newborn girl is noted to have stippled epiphyses on radiographs, nasal hypoplasia, and short distal phalanges. Her mother was treated for a chronic medical condition throughout her pregnancy. Maternal use of which of the following medications most likely caused this phenocopy of chondrodysplasia punctata?

. Phenytoin
. Warfarin
. Valproic acid
. Lithium
. Isotretinoin

Correct Answer & Explanation

. Warfarin

Explanation

Warfarin is a known teratogen that inhibits vitamin K-dependent bone proteins like osteocalcin. Fetal warfarin syndrome clinically and radiographically mimics the stippled epiphyses and nasal hypoplasia seen in chondrodysplasia punctata.

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