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1. General Principles & Basic Science MCQs

Practice Set 457 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 9121

Topic: Biology, Genetics & Bone Healing

An asymptomatic 68-year-old male undergoes a routine pelvic radiograph which demonstrates cortical thickening and sclerosis of the right iliopectineal line (Brim sign).

What is the classic serum laboratory profile associated with this condition?

. Low Calcium, High Phosphate, High Alkaline Phosphatase
. High Calcium, Low Phosphate, High Alkaline Phosphatase
. Normal Calcium, Normal Phosphate, High Alkaline Phosphatase
. Normal Calcium, Normal Phosphate, Normal Alkaline Phosphatase

Correct Answer & Explanation

. Normal Calcium, Normal Phosphate, High Alkaline Phosphatase

Explanation

The radiograph demonstrates Paget's disease of the pelvis. Paget's disease is characterized by markedly elevated alkaline phosphatase reflecting high bone turnover, while serum calcium and phosphate levels typically remain within normal limits.

Question 9122

Topic: 1. General Principles & Basic Science

A 55-year-old male with chronic untreated joint pain presents with palpable nodular masses around his joints. Radiographs of his feet are obtained.

Which radiographic description best characterizes the classic bony erosions seen in this condition?

. Marginal erosions with symmetric diffuse joint space narrowing
. Central articular erosions yielding a 'gull-wing' appearance
. Punched-out juxta-articular erosions with overhanging sclerotic edges
. Subchondral cysts with large marginal osteophytes

Correct Answer & Explanation

. Punched-out juxta-articular erosions with overhanging sclerotic edges

Explanation

Chronic tophaceous gout radiographically presents as well-defined, 'punched-out' juxta-articular erosions with sclerotic borders and characteristic 'overhanging edges' (Martel's sign). Joint spaces are typically preserved until late in the disease process.

Question 9123

Topic: 1. General Principles & Basic Science

In a patient with end-stage renal disease who develops secondary hyperparathyroidism, what is the primary pathophysiological trigger for the parathyroid gland hyperplasia?

. Autonomous hypersecretion of parathyroid hormone by a primary adenoma
. Decreased renal excretion of phosphate leading to hypocalcemia
. Increased renal synthesis of 1,25-dihydroxyvitamin D
. Primary overproduction of fibroblast growth factor 23 (FGF23) in bone

Correct Answer & Explanation

. Decreased renal excretion of phosphate leading to hypocalcemia

Explanation

In chronic kidney disease, impaired phosphate excretion leads to hyperphosphatemia, which complexes with serum calcium to cause hypocalcemia. This low serum calcium, combined with decreased renal calcitriol production, chronically stimulates the parathyroid glands to overproduce PTH.

Question 9124

Topic: Biology, Genetics & Bone Healing

A 72-year-old male with symptomatic Paget's disease involving the right hemipelvis and proximal femur is scheduled for a total hip arthroplasty. What perioperative medical management is highly recommended to minimize surgical complications?

. Preoperative administration of bisphosphonates to decrease bone vascularity
. Preoperative administration of teriparatide to stimulate bone formation
. High-dose Vitamin D supplementation to prevent postoperative hypocalcemia
. Prophylactic systemic corticosteroids to prevent acute inflammatory flare

Correct Answer & Explanation

. Preoperative administration of bisphosphonates to decrease bone vascularity

Explanation

Pagetic bone is highly vascular during the active disease phase, which poses a significant risk for massive intraoperative hemorrhage during arthroplasty. Preoperative treatment with bisphosphonates helps decrease bone turnover and vascularity, minimizing intraoperative blood loss.

Question 9125

Topic: 1. General Principles & Basic Science

A 40-year-old male develops his first acute gout flare in the great toe two weeks after his primary care physician started him on a new antihypertensive medication. Which of the following medications most likely precipitated this event by decreasing renal uric acid excretion?

. Losartan
. Amlodipine
. Hydrochlorothiazide
. Lisinopril

Correct Answer & Explanation

. Hydrochlorothiazide

Explanation

Thiazide diuretics (like hydrochlorothiazide) compete with uric acid for secretion in the proximal convoluted tubule, leading to decreased urate clearance and hyperuricemia. This can readily precipitate an acute gout attack. Conversely, Losartan has mild uricosuric properties.

Question 9126

Topic: Biology, Genetics & Bone Healing
An 80-year-old male complains of progressive bilateral hearing loss. A lateral skull radiograph demonstrates mixed radiolucent and radiopaque areas with marked thickening of the calvarium. What is the classic descriptive term for this radiographic appearance?
. Salt and pepper skull
. Hair-on-end appearance
. Cotton wool appearance
. Punched-out lytic lesions

Correct Answer & Explanation

. Cotton wool appearance

Explanation

The 'cotton wool' skull is the classic radiographic finding in the mixed osteolytic-osteosclerotic phase of Paget's disease. The patient's hearing loss is due to cranial nerve VIII compression from bony overgrowth in the temporal bone.

Question 9127

Topic: Infection, Pharmacology & VTE

A 58-year-old male hospitalized for severe COPD exacerbation develops acute, intense swelling and erythema in his left knee. Synovial fluid analysis confirms acute gout. He has Stage 4 chronic kidney disease (eGFR 20 mL/min). What is the safest acute treatment option?

. Oral indomethacin
. Intravenous colchicine
. Intra-articular or systemic corticosteroids
. Initiation of oral allopurinol

Correct Answer & Explanation

. Intra-articular or systemic corticosteroids

Explanation

In patients with severe chronic kidney disease, NSAIDs are contraindicated due to nephrotoxicity, and colchicine clearance is dangerously impaired. Intra-articular or systemic corticosteroids are the safest and most effective option for acute gout flares in this demographic.

Question 9128

Topic: Biology, Genetics & Bone Healing

A patient with symptomatic Paget's disease is started on zoledronic acid. What is the specific cellular mechanism of action of this medication?

. It inhibits farnesyl pyrophosphate synthase in the mevalonate pathway of osteoclasts
. It stimulates osteoprotegerin (OPG) production by osteoblasts
. It binds competitively to RANK-ligand, preventing osteoclast activation
. It inhibits osteoblast differentiation and collagen synthesis

Correct Answer & Explanation

. It inhibits farnesyl pyrophosphate synthase in the mevalonate pathway of osteoclasts

Explanation

Nitrogen-containing bisphosphonates, such as zoledronic acid, act by inhibiting farnesyl pyrophosphate synthase in the mevalonate pathway. This disrupts essential intracellular signaling in osteoclasts, leading to cytoskeletal dysfunction and apoptosis.

Question 9129

Topic: Biology, Genetics & Bone Healing

A 50-year-old female is incidentally diagnosed with asymptomatic primary hyperparathyroidism during routine labs. Which of the following is considered an accepted criterion for recommending parathyroidectomy in this asymptomatic patient?

. Serum calcium > 0.5 mg/dL above the upper limit of normal
. A dual-energy x-ray absorptiometry (DEXA) T-score < -2.5 at any site
. Age greater than 60 years
. 24-hour urine calcium < 100 mg

Correct Answer & Explanation

. A dual-energy x-ray absorptiometry (DEXA) T-score < -2.5 at any site

Explanation

According to the consensus guidelines, indications for parathyroidectomy in asymptomatic primary hyperparathyroidism include age < 50 years, serum calcium > 1.0 mg/dL above normal, T-score < -2.5 (osteoporosis), and reduced creatinine clearance (< 60 mL/min).

Question 9130

Topic: Biology, Genetics & Bone Healing

A bone biopsy is obtained from a thickened, clinically warm tibia in a 70-year-old male to rule out malignancy.

If this lesion represents the classic underlying metabolic disease, what is the histological hallmark expected on biopsy?

. Osteoid seams with completely absent mineralization
. A 'mosaic' pattern of lamellar bone with prominent, haphazard cement lines
. Replacement of marrow with spindle cells, giant cells, and hemosiderin
. Extensive avascular necrosis with empty osteocyte lacunae

Correct Answer & Explanation

. A 'mosaic' pattern of lamellar bone with prominent, haphazard cement lines

Explanation

The histologic hallmark of Paget's disease is a 'mosaic' or 'jigsaw puzzle' pattern of lamellar bone. This results from chaotic, rapid cycles of bone resorption and formation, creating haphazardly arranged, prominent cement lines.

Question 9131

Topic: 1. General Principles & Basic Science

A 45-year-old male presents with an acutely painful, swollen, and erythematous first metatarsophalangeal joint.

Synovial fluid aspiration is performed. Under compensated polarized light microscopy, what crystal characteristics confirm the suspected diagnosis?

. Rhomboid-shaped, weakly positively birefringent
. Needle-shaped, strongly negatively birefringent
. Envelope-shaped, positively birefringent
. Bipyramidal, non-birefringent
. Square-shaped, negatively birefringent

Correct Answer & Explanation

. Needle-shaped, strongly negatively birefringent

Explanation

The clinical presentation is classic for acute gout (podagra). Gout is caused by monosodium urate crystals, which appear needle-shaped and strongly negatively birefringent (yellow when parallel to the compensator axis).

Question 9132

Topic: Biology, Genetics & Bone Healing

A 70-year-old female with active polyostotic Paget's disease requires an elective total hip arthroplasty for severe secondary osteoarthritis. To minimize intraoperative blood loss, which of the following is the most appropriate preoperative medical intervention?

. Preoperative administration of intravenous bisphosphonates 2 to 3 months prior to surgery
. Preoperative administration of denosumab 1 week prior to surgery
. Administration of high-dose corticosteroids 48 hours prior to surgery
. Initiation of teriparatide therapy 4 weeks prior to surgery
. No specific preoperative medical management is indicated

Correct Answer & Explanation

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

Explanation

Total joint arthroplasty in active Paget's disease is associated with massive blood loss due to hypervascularity of the bone. Pretreatment with bisphosphonates for 2 to 3 months preoperatively reduces disease activity, vascularity, and subsequent blood loss.

Question 9133

Topic: 1. General Principles & Basic Science

Which of the following radiographic features is considered pathognomonic for chronic tophaceous gout?

. Subchondral cysts with joint space narrowing and osteophytes
. Pencil-in-cup deformity of the distal interphalangeal joints
. Punched-out periarticular erosions with overhanging sclerotic margins
. Chondrocalcinosis of the articular cartilage and menisci
. Juxta-articular osteopenia with marginal erosions

Correct Answer & Explanation

. Punched-out periarticular erosions with overhanging sclerotic margins

Explanation

Chronic gout is characterized radiographically by 'punched-out' periarticular lytic lesions with overhanging sclerotic margins (Martel sign). The joint space is often preserved until late in the disease process.

Question 9134

Topic: Biology, Genetics & Bone Healing

Paget's disease of bone progresses through three distinct pathophysiological phases. Which cellular mechanism initiates the primary lytic phase of the disease?

. Intense and unregulated osteoblastic bone formation
. Apoptosis of osteocytes leading to empty lacunae
. Massive recruitment and overactivity of abnormal multinucleated osteoclasts
. Infiltration of the marrow space by plasma cells
. Defective mineralization of osteoid by osteoblasts

Correct Answer & Explanation

. Massive recruitment and overactivity of abnormal multinucleated osteoclasts

Explanation

The initial phase of Paget's disease is the lytic phase, characterized by profound, unregulated bone resorption driven by abnormal, enlarged, and multinucleated osteoclasts. This is followed by a mixed phase and finally a sclerotic phase.

Question 9135

Topic: 1. General Principles & Basic Science

A 55-year-old female presents with lethargy, abdominal pain, and bone pain. Laboratory evaluation reveals elevated serum parathyroid hormone (PTH). Which set of additional laboratory findings confirms the diagnosis of primary hyperparathyroidism?

. Elevated serum calcium, decreased serum phosphorus
. Decreased serum calcium, elevated serum phosphorus
. Normal serum calcium, elevated serum phosphorus
. Elevated serum calcium, elevated serum phosphorus
. Decreased serum calcium, decreased serum phosphorus

Correct Answer & Explanation

. Elevated serum calcium, decreased serum phosphorus

Explanation

Primary hyperparathyroidism is typically caused by a parathyroid adenoma. It classically presents with elevated PTH, leading to hypercalcemia and hypophosphatemia due to increased bone resorption and renal calcium retention/phosphorus excretion.

Question 9136

Topic: 1. General Principles & Basic Science

A 52-year-old man with recurrent gout attacks is prescribed a medication for long-term management to prevent future flares. The prescribed medication works by inhibiting xanthine oxidase. What is this medication?

. Probenecid
. Colchicine
. Indomethacin
. Allopurinol
. Pegloticase

Correct Answer & Explanation

. Allopurinol

Explanation

Allopurinol is a first-line urate-lowering therapy for chronic gout that functions by inhibiting xanthine oxidase, thereby decreasing uric acid production. Colchicine and indomethacin are used for acute flares, while probenecid increases renal uric acid excretion.

Question 9137

Topic: Biology, Genetics & Bone Healing

In a patient suspected of having Paget's disease, what is the most sensitive imaging modality for identifying the extent of polyostotic skeletal involvement?

. Computed Tomography (CT) without contrast
. Magnetic Resonance Imaging (MRI) with gadolinium
. Technetium-99m bone scintigraphy
. Positron Emission Tomography (PET)
. Skeletal survey with plain radiographs

Correct Answer & Explanation

. Technetium-99m bone scintigraphy

Explanation

A Technetium-99m bone scan is highly sensitive for detecting active bone lesions in Paget's disease and is the imaging study of choice to determine the full extent of skeletal involvement. It shows intense, homogeneously increased uptake in affected bones.

Question 9138

Topic: Infection, Pharmacology & VTE

A 60-year-old male with an acute gout flare in his knee has a medical history significant for stage 4 chronic kidney disease and a recent bleeding gastric ulcer. Which is the safest and most appropriate acute treatment option for his knee?

. High-dose oral ibuprofen
. Oral colchicine
. Oral probenecid
. Intra-articular corticosteroid injection
. Oral indomethacin

Correct Answer & Explanation

. Intra-articular corticosteroid injection

Explanation

NSAIDs and colchicine are generally contraindicated or require extreme caution in patients with severe chronic kidney disease or active peptic ulcer disease. An intra-articular corticosteroid injection provides effective localized relief with minimal systemic risk.

Question 9139

Topic: Biomechanics & Biomaterials

A 60-year-old man presents with chronic pain and swelling in his left big toe. Radiographs show a well-defined periarticular erosion with an 'overhanging margin' and preserved joint space.

What is the primary composition of the crystalline deposit responsible for this lesion?

. Calcium pyrophosphate dihydrate
. Monosodium urate
. Basic calcium phosphate
. Cholesterol
. Calcium hydroxyapatite

Correct Answer & Explanation

. Monosodium urate

Explanation

The classic 'rat-bite' erosions with overhanging sclerotic margins and preserved joint space are hallmark radiographic findings of gout. Gout is caused by the deposition of monosodium urate crystals.

Question 9140

Topic: 1. General Principles & Basic Science

A 55-year-old woman is evaluated for generalized bone pain and recurrent nephrolithiasis. Dual-energy x-ray absorptiometry reveals severe cortical bone loss. Her laboratory profile will most likely show which of the following?

. Decreased calcium, increased phosphorus, increased PTH
. Increased calcium, decreased phosphorus, increased PTH
. Normal calcium, normal phosphorus, increased alkaline phosphatase
. Increased calcium, increased phosphorus, decreased PTH
. Decreased calcium, decreased phosphorus, increased PTH

Correct Answer & Explanation

. Increased calcium, decreased phosphorus, increased PTH

Explanation

Primary hyperparathyroidism, usually caused by a parathyroid adenoma, is characterized by hypercalcemia, hypophosphatemia, and elevated parathyroid hormone (PTH) levels. PTH stimulates osteoclastic bone resorption, preferentially affecting cortical bone.

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