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1. General Principles & Basic Science MCQs

Practice Set 760 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 15181

Topic: Biology, Genetics & Bone Healing

A 62-year-old man with a history of recurrent monoarticular arthritis presents with chronic pain and deformity in his foot. Radiographs display well-defined, "punched-out" erosions with sclerotic margins and overhanging edges in the first metatarsophalangeal joint. What is the underlying pathophysiology of this condition?

. Underexcretion or overproduction of uric acid
. Autoimmune destruction of articular cartilage
. Deposition of calcium pyrophosphate dihydrate
. Defect in type I collagen synthesis
. Overactivity of osteoclasts

Correct Answer & Explanation

. Underexcretion or overproduction of uric acid

Explanation

The clinical and radiographic findings are classic for chronic tophaceous gout. It is caused by hyperuricemia, most commonly due to renal underexcretion (90%), or less commonly, overproduction of uric acid.

Question 15182

Topic: Biology, Genetics & Bone Healing

A 72-year-old man with symptomatic Paget's disease involving the pelvis and femur is scheduled for a total hip arthroplasty due to severe secondary osteoarthritis. Which preoperative medication should be considered to reduce intraoperative blood loss and disease activity?

. Colchicine
. Allopurinol
. Teriparatide
. Bisphosphonates
. Methotrexate

Correct Answer & Explanation

. Bisphosphonates

Explanation

Preoperative administration of bisphosphonates is recommended in patients with active Paget's disease undergoing elective orthopedic surgery. It reduces the hypervascularity of the pagetic bone, thereby significantly decreasing intraoperative blood loss.

Question 15183

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 15184

Topic: Biology, Genetics & Bone Healing
An 80-year-old woman with advanced Paget's disease of the skull presents with gradual hearing loss and tinnitus. What is the primary cause of hearing loss in this patient?
. Microvascular ischemia of the cochlear nerve
. Autoimmune destruction of the inner ear
. Bony overgrowth narrowing the internal auditory canal
. Ototoxicity from bisphosphonate therapy
. Chronic otitis media

Correct Answer & Explanation

. Bony overgrowth narrowing the internal auditory canal

Explanation

Hearing loss in Paget's disease of the skull (osteitis deformans) is the most common neurologic complication. It is primarily caused by bony overgrowth narrowing the cranial foramina, leading to compression of the vestibulocochlear nerve (CN VIII).

Question 15185

Topic: Biology, Genetics & Bone Healing

A 65-year-old man with Paget's disease presents for a routine follow-up complaining of progressive hearing loss. Which of the following is the primary mechanism of action of the first-line medication used to treat the symptomatic manifestations of this condition?

. Inhibition of farnesyl pyrophosphate synthase
. Direct inhibition of osteoblast activity
. Activation of RANK ligand
. Inhibition of xanthine oxidase
. Binding to parathyroid hormone receptors

Correct Answer & Explanation

. Inhibition of farnesyl pyrophosphate synthase

Explanation

First-line treatment for symptomatic Paget's disease, including cranial nerve entrapment causing hearing loss, is a nitrogen-containing bisphosphonate. These drugs inhibit farnesyl pyrophosphate synthase, leading to osteoclast apoptosis and decreased bone resorption.

Question 15186

Topic: 1. General Principles & Basic Science

A 52-year-old male with a history of recurrent podagra presents with a painful, nodular mass on his first metatarsophalangeal joint.

Radiographs are obtained. Which of the following radiographic features is most characteristic of chronic tophaceous gout?

. Pencil-in-cup deformity
. Subchondral cysts with joint space narrowing
. Punched-out erosions with overhanging sclerotic margins
. Subperiosteal bone resorption
. Central erosions creating a gull-wing appearance

Correct Answer & Explanation

. Punched-out erosions with overhanging sclerotic margins

Explanation

Chronic gout is classically associated with punched-out juxta-articular erosions featuring sclerotic, overhanging margins known as Martel's sign. Joint space is often preserved until late in the disease process.

Question 15187

Topic: Biology, Genetics & Bone Healing

A 48-year-old female with chronic kidney disease presents with diffuse back pain. Spine radiographs reveal alternating bands of radiolucency and radiodensity in the vertebral bodies. Which of the following underlying pathophysiologic processes is most directly responsible for this radiographic finding?

. Accumulation of unmineralized osteoid
. Chronic stimulation of osteoclasts by elevated parathyroid hormone
. Deposition of monosodium urate crystals
. Disorganized remodeling by multinucleated giant osteoclasts
. Deposition of calcium pyrophosphate dihydrate

Correct Answer & Explanation

. Chronic stimulation of osteoclasts by elevated parathyroid hormone

Explanation

The radiograph describes a Rugger-Jersey spine, characteristic of secondary hyperparathyroidism in renal osteodystrophy. It results from chronic parathyroid hormone (PTH) stimulation leading to endplate sclerosis and central vertebral lucency.

Question 15188

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 15189

Topic: Biology, Genetics & Bone Healing

A 72-year-old man undergoes a biopsy of a thickened, enlarged tibia exhibiting a bowing deformity. Histological examination of the bone reveals a mosaic pattern of lamellar bone with prominent cement lines. Which of the following cell types is initially responsible for the pathogenesis of this disease?

. Osteoblasts
. Osteoclasts
. Osteocytes
. Chondrocytes
. Fibroblasts

Correct Answer & Explanation

. Osteoclasts

Explanation

Paget's disease initiates with an intensely osteolytic phase driven by large, overactive, multinucleated osteoclasts. This is followed by a mixed phase and a sclerotic phase, resulting in disorganized lamellar bone with characteristic cement lines.

Question 15190

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 15191

Topic: Biology, Genetics & Bone Healing

A 75-year-old male with long-standing polyostotic Paget's disease is scheduled for an elective total hip arthroplasty. To minimize perioperative blood loss associated with the hypervascular pagetic bone, which of the following preoperative interventions is most appropriate?

. Preoperative administration of bisphosphonates 2-3 months prior to surgery
. Administration of fresh frozen plasma immediately before incision
. Initiation of high-dose corticosteroids 1 week prior to surgery
. Preoperative administration of teriparatide
. Preoperative radiation therapy to the affected hip

Correct Answer & Explanation

. Preoperative administration of bisphosphonates 2-3 months prior to surgery

Explanation

Pagetic bone is highly vascular during active phases, leading to a significant risk of intraoperative hemorrhage during orthopedic surgery. Pretreatment with bisphosphonates for 2-3 months reduces disease activity and bone vascularity, thereby minimizing blood loss.

Question 15192

Topic: 1. General Principles & Basic Science

A 45-year-old male with chronic tophaceous gout is started on long-term urate-lowering therapy. Six weeks later, his serum uric acid levels are significantly reduced. What is the mechanism of action of the most commonly prescribed first-line medication for this purpose?

. Inhibition of microtubule polymerization
. Competitive inhibition of xanthine oxidase
. Increased renal excretion of uric acid by inhibiting URAT1
. Recombinant uricase that converts uric acid to allantoin
. Inhibition of cyclooxygenase-2

Correct Answer & Explanation

. Competitive inhibition of xanthine oxidase

Explanation

Allopurinol is the first-line urate-lowering therapy for chronic gout. It functions as a competitive inhibitor of xanthine oxidase, preventing the conversion of hypoxanthine to xanthine, and xanthine to uric acid.

Question 15193

Topic: 1. General Principles & Basic Science

A 55-year-old male with chronic renal failure presents with knee pain. Labs reveal hypocalcemia, hyperphosphatemia, and an extremely high PTH level. Radiographs show subperiosteal resorption. Which of the following combinations of laboratory findings is most characteristic of primary hyperparathyroidism, distinguishing it from this patient's condition?

. High calcium, high phosphate, high PTH
. High calcium, low phosphate, high PTH
. Low calcium, high phosphate, high PTH
. Low calcium, low phosphate, high PTH
. Normal calcium, normal phosphate, low PTH

Correct Answer & Explanation

. High calcium, low phosphate, high PTH

Explanation

Primary hyperparathyroidism is typically caused by a parathyroid adenoma, resulting in elevated PTH, elevated serum calcium, and decreased serum phosphate. This contrasts with secondary hyperparathyroidism from renal failure, which presents with low or normal calcium and high phosphate.

Question 15194

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 15195

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 15196

Topic: 1. General Principles & Basic Science

A 50-year-old man presents with a painful, swollen first MTP joint. Joint aspirate reveals needle-shaped crystals. When aligned parallel to the axis of the compensator under polarized light microscopy, what color do these crystals typically appear?

. Blue
. Yellow
. Green
. Red
. Colorless

Correct Answer & Explanation

. Yellow

Explanation

Gout is caused by monosodium urate crystals, which are strongly negatively birefringent. They appear yellow when aligned parallel to the axis of the compensator and blue when perpendicular.

Question 15197

Topic: Biology, Genetics & Bone Healing

A 72-year-old man with active Paget's disease of the proximal femur is scheduled for an elective total hip arthroplasty due to severe secondary osteoarthritis. His alkaline phosphatase is markedly elevated. Which preoperative intervention is most appropriate to reduce surgical complications?

. Preoperative radiation therapy
. Administration of an IV bisphosphonate
. Administration of calcitonin
. Prophylactic embolization
. Initiation of methotrexate

Correct Answer & Explanation

. Administration of an IV bisphosphonate

Explanation

Pagetoid bone is highly vascular, posing a significant risk of massive intraoperative hemorrhage. Preoperative treatment with bisphosphonates (1 to 3 months prior) reduces disease activity, normalizing vascularity and decreasing surgical blood loss.

Question 15198

Topic: Biology, Genetics & Bone Healing

A 48-year-old woman presents with a lytic lesion in her distal radius. Biopsy reveals sheets of osteoclast-like multinucleated giant cells in a background of spindle cells and abundant hemosiderin. Lab evaluation shows elevated serum calcium and intact PTH. What is the underlying pathogenesis of this bone lesion?

. Neoplastic proliferation of osteoblasts
. Accumulation of monosodium urate
. Extreme osteoclastic bone resorption and microhemorrhage
. Abnormal woven bone formation with a SQSTM1 mutation
. Infection with pyogenic organisms

Correct Answer & Explanation

. Extreme osteoclastic bone resorption and microhemorrhage

Explanation

The lesion is a brown tumor of hyperparathyroidism (osteitis fibrosa cystica). It arises from intense osteoclastic activity leading to bone resorption, microhemorrhages, and subsequent hemosiderin deposition, which gives it a brown color.

Question 15199

Topic: Biology, Genetics & Bone Healing

First-line medical therapy for symptomatic Paget's disease involves a class of drugs that potently inhibit bone resorption. What is the primary molecular target of the nitrogen-containing agents in this class?

. RANK ligand
. Farnesyl pyrophosphate synthase
. Sclerostin
. Cathepsin K
. Osteoprotegerin

Correct Answer & Explanation

. Farnesyl pyrophosphate synthase

Explanation

Nitrogen-containing bisphosphonates (e.g., zoledronic acid) are the first-line treatment for active Paget's disease. They work by inhibiting farnesyl pyrophosphate synthase within the mevalonate pathway, ultimately leading to osteoclast apoptosis.

Question 15200

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.

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