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1. General Principles & Basic Science MCQs

Practice Set 45 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 881

Topic: Infection, Pharmacology & VTE
A 74-year-old man with previously stable emphysema presents to the emergency department with right-sided pleuritic chest pain and sudden increase in shortness of breath. There are no other associated symptoms and no signs to suggest acute infection. There appears to be decreased vocal resonance over the upper right side of the chest. Which is the most likely diagnosis in this case?
. Acute-onset pneumonia
. An exacerbation of COPD
. A spontaneous pneumothorax
. Empyema
. Pulmonary embolism

Correct Answer & Explanation

. A spontaneous pneumothorax

Explanation

Correct Answer: C - A spontaneous pneumothorax. Explanation: Underlying COPD is the usual cause of pneumothorax in patients of this age group. The sudden onset of shortness of breath associated with pleuritic chest pain and the absence of infective symptoms make pneumothorax more likely than COPD exacerbation or pneumonia. Decreased vocal resonance is a classic sign of pneumothorax.

Question 882

Topic: 1. General Principles & Basic Science
A 62-year-old heavy smoker comes to the emergency department with a persistent cough and severe shortness of breath, meaning that he is unable to lie down flat in bed. He has a history of hypertension, chronic obstructive pulmonary disease (COPD), and a previous inferior myocardial infarction. On examination, his BP is 155/72 mmHg, pulse is 80 bpm and regular. He has coarse crackles and wheeze consistent with his diagnosis of COPD on auscultation of the chest. You can feel supraclavicular lymphadenopathy. Investigations: Hb 12.0 g/dl, WCC 10.9 × 10^9/l, PLT 199 × 10^9/l, ESR 72 mm/1st hour, Na+ 138 mmol/l, K+ 4.0 mmol/l, Creatinine 120 μmol/l, ALT 230 U/l, Bilirubin 17 μmol/l, ALP 199 U/l. Chest X-ray (CXR) shows evidence of a mediastinal mass and lymphadenopathy (previous X-ray did not show these changes 3 months earlier). Which one of the following is the most likely diagnosis?
. Adenocarcinoma of the lung
. Bronchoalveolar carcinoma
. Large-cell lung carcinoma
. Small-cell lung carcinoma
. Squamous-cell lung carcinoma

Correct Answer & Explanation

. Small-cell lung carcinoma

Explanation

Of the options given, only small-cell lung cancer progresses rapidly enough to move from no changes on CXR to significant changes within only 3 months. The abnormal liver function raises the possibility of hepatic metastases. Up to 70% of patients with small-cell lung cancer are recognized to have disseminated disease at the time of presentation.

Question 883

Topic: Biology, Genetics & Bone Healing
During the process of secondary bone healing, a soft callus forms at the fracture site to bridge the gap before endochondral ossification occurs. What type of collagen is most predominant in this soft callus phase?
. Type I collagen
. Type II collagen
. Type III collagen
. Type IV collagen
. Type X collagen

Correct Answer & Explanation

. Type II collagen

Explanation

The soft callus primarily consists of fibrocartilage, making Type II collagen the predominant type during this phase. As endochondral ossification progresses, it is gradually replaced by woven bone, which is predominantly Type I collagen.

Question 884

Topic: Biology, Genetics & Bone Healing

A 55-year-old patient with poorly controlled diabetes mellitus presents with a swollen, erythematous, and warm foot with a new 'rocker-bottom' deformity, but minimal pain. What is the proposed pathophysiology of the bone destruction in the active, acute phase of Charcot neuroarthropathy according to the neurovascular theory?

. Microvascular thrombosis leading to avascular necrosis
. Autonomic neuropathy causing increased perfusion and bone resorption
. Direct bacterial invasion of the bone
. Autoimmune destruction of articular cartilage
. Venous stasis leading to periosteal new bone formation

Correct Answer & Explanation

. Autonomic neuropathy causing increased perfusion and bone resorption

Explanation

The neurovascular theory posits that autonomic neuropathy results in loss of sympathetic tone, causing vasodilation, hyperemia, and increased active bone resorption by osteoclasts, which subsequently leads to mechanical failure and fractures.

Question 885

Topic: Biology, Genetics & Bone Healing

A 65-year-old female with severe osteoporosis is being treated with Denosumab to reduce her risk of pathologic fractures. What is the specific mechanism of action of this medication?

. Binds directly to osteoclast ruffled borders
. Stimulates osteoblast differentiation via Wnt signaling
. Monoclonal antibody targeting RANKL
. Inhibits farnesyl pyrophosphate synthase
. Recombinant parathyroid hormone analog

Correct Answer & Explanation

. Monoclonal antibody targeting RANKL

Explanation

Denosumab is a human monoclonal antibody that binds to Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL), preventing its interaction with RANK on osteoclasts. This inhibits osteoclast formation, function, and survival.

Question 886

Topic: Biology, Genetics & Bone Healing

A 30-year-old female presents with knee pain. Radiographs show a distinct, eccentrically located lytic epiphyseal lesion in the proximal tibia. Biopsy confirms multinucleated giant cells resembling osteoclasts. Which targeted systemic therapy is most appropriate as an adjuvant?

. Denosumab
. Infliximab
. Rituximab
. Methotrexate
. Teriparatide

Correct Answer & Explanation

. Denosumab

Explanation

Denosumab is a monoclonal antibody against RANKL. It prevents the maturation of osteoclast-like giant cells, making it a highly effective treatment for Giant Cell Tumor of bone.

Question 887

Topic: Surgical Anatomy & Approaches

A 25-year-old male sustains an anterior shoulder dislocation during a rugby tackle. Following successful closed reduction, he notes persistent numbness over the lateral aspect of his deltoid muscle. Which nerve is most likely injured?

. Radial nerve
. Musculocutaneous nerve
. Axillary nerve
. Median nerve
. Suprascapular nerve

Correct Answer & Explanation

. Axillary nerve

Explanation

The axillary nerve is the most frequently injured nerve during anterior shoulder dislocations. It supplies motor innervation to the deltoid and teres minor, and sensory innervation to the skin over the lateral shoulder.

Question 888

Topic: Infection, Pharmacology & VTE

A 40-year-old African American female presents with sausage-like swelling of her digits (dactylitis). Hand radiographs demonstrate multiple well-defined, cyst-like radiolucencies in the phalanges with a lace-like trabecular pattern. Chest X-ray shows bilateral hilar lymphadenopathy. What is the most likely diagnosis?

. Tuberculosis
. Enchondromatosis
. Sarcoidosis
. Gout
. Osteomyelitis

Correct Answer & Explanation

. Sarcoidosis

Explanation

Sarcoidosis can cause osseous involvement in 5-10% of patients, classically presenting as cyst-like lesions in the phalanges and dactylitis. This correlates strongly with the bilateral hilar lymphadenopathy seen on chest radiography.

Question 889

Topic: Biology, Genetics & Bone Healing

A 72-year-old male presents with increasing pain in his right thigh and increasing hat size. Radiographs of the femur show cortical thickening, coarse trabeculation, and a bowing deformity. Laboratory studies show a significantly elevated alkaline phosphatase with normal calcium and phosphorus. Which of the following is the primary cellular defect?

. Decreased osteoblast function
. Increased osteoclast activity followed by chaotic osteoblast activity
. Impaired mineralization of osteoid
. Fibroblast proliferation replacing bone marrow
. Monoclonal plasma cell proliferation

Correct Answer & Explanation

. Increased osteoclast activity followed by chaotic osteoblast activity

Explanation

Paget's disease of bone is characterized by an initial phase of furious osteoclastic bone resorption followed by a disorganized, chaotic phase of osteoblastic bone formation. This results in structurally weak, woven bone.

Question 890

Topic: 1. General Principles & Basic Science

A 35-year-old female with severe, persistent asthma managed with long-term oral prednisone presents with insidious onset of groin pain with weight-bearing. Radiographs of the hip are normal. MRI shows a focal subchondral band of low signal intensity in the anterosuperior femoral head on T1-weighted images. What is the most likely diagnosis?

. Transient osteoporosis of the hip
. Osteoarthritis
. Avascular necrosis (osteonecrosis)
. Septic arthritis
. Femoral neck stress fracture

Correct Answer & Explanation

. Avascular necrosis (osteonecrosis)

Explanation

Long-term corticosteroid use is a major risk factor for avascular necrosis of the femoral head. MRI is the most sensitive imaging modality, typically showing a well-demarcated subchondral band of low T1 signal.

Question 891

Topic: Biology, Genetics & Bone Healing

A 50-year-old male with end-stage renal disease on hemodialysis presents with diffuse bone pain. Radiographs reveal subperiosteal bone resorption in the phalanges and a "rugger jersey" spine. Which of the following laboratory profiles is expected?

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

Correct Answer & Explanation

. Low calcium, high phosphate, high PTH

Explanation

Renal osteodystrophy (secondary hyperparathyroidism) results from phosphate retention and failure of the kidneys to convert Vitamin D to its active form. This leads to hypocalcemia, hyperphosphatemia, and a compensatory significant rise in parathyroid hormone (PTH).

Question 892

Topic: Biology, Genetics & Bone Healing

A 14-year-old girl is evaluated for recurrent fractures following minor trauma. She also has a history of severe anemia and cranial nerve palsies. Radiographs reveal generalized dense, sclerotic bones with absent medullary canals and an "Erlenmeyer flask" deformity of the distal femurs. The pathogenesis involves a defect in which of the following?

. Type I collagen synthesis
. Osteoclast ruffled border function
. Fibroblast growth factor receptor 3 (FGFR3)
. Vitamin D receptor
. Runx2/Cbfa1 transcription factor

Correct Answer & Explanation

. Osteoclast ruffled border function

Explanation

Osteopetrosis (marble bone disease) is caused by defective osteoclastic bone resorption, often due to a failure to form the ruffled border. This results in dense, brittle bones that obliterate the marrow space, leading to cytopenias.

Question 893

Topic: 1. General Principles & Basic Science
A 43-year-old woman is referred by her general practitioner with a productive cough and inspiratory crackles at the left base. Which one of the following is considered to be a core adverse prognostic factor under the CURB-65 criteria?
. Bilateral changes on chest X-ray
. Blood pressure 98/65 mmHg
. Oxygen saturation 92% on room air
. Respiratory rate of 28/min
. Serum urea 7.1 mmol/l

Correct Answer & Explanation

. Serum urea 7.1 mmol/l

Explanation

Correct Answer: E - Serum urea 7.1 mmol/l. A urea >7 mmol/l is associated with an adverse prognosis and is a component of the CURB-65 scoring system. Core clinical adverse prognostic factors are summarised using the abbreviation CURB-65: Confusion (new onset) with a mini-mental test score of less than 8, Urea > 7.0 mmol/l, Respiratory rate > 30/min, Blood pressure (systolic < 90 mmHg or diastolic < 60 mmHg), and 65 or older (age). If any of these core clinical features is present, the patient is at increased risk of death and should not be sent home (British Thoracic Society Guidelines, December 2001). Bilateral changes on chest X-ray is incorrect; although multilobar involvement can signify an adverse prognosis in pneumonia, it does not feature as part of the CURB-65 scoring system. Blood pressure 98/65 mmHg is incorrect; although blood pressure is used as part of CURB-65 scoring, the value mentioned would not signify an adverse prognosis. Oxygen saturation 92% on room air is incorrect; although hypoxia can signify an adverse prognosis in pneumonia, it does not feature as part of the CURB-65 scoring system. Respiratory rate of 28/min is incorrect; although respiratory rate is used as part of CURB-65 scoring, the value mentioned would not signify an adverse prognosis.

Question 894

Topic: 1. General Principles & Basic Science

A 42-year-old patient was diagnosed with mediastinal tuberculosis 3 weeks ago and commenced on treatment. He presents with worsening breathlessness and stridor. His chest X-ray shows mediastinal lymph nodes that are compressing the carina; although he is distressed, he is alert and orientated and maintaining his oxygenation. You give him an injection of hydrocortisone. What is the next step in the investigation and/or management?

. Broad-spectrum antibiotics
. Ethambutol
. Heparin
. Tracheostomy
. Urgent computed tomography (CT) scan

Correct Answer & Explanation

. Urgent computed tomography (CT) scan

Explanation

Correct Answer: E- Urgent computed tomography (CT) scan Explanation Urgent computed tomography (CT) scan The computed tomographic (CT) scan is the most appropriate investigation. On enhanced CT scans, nodes larger than 2 cm in diameter invariably show central areas of low attenuation and peripheral rim enhancement. Enhanced walls are usually irregular in thickness. CT scan is useful prior to commencing steroid therapy, first to confirm the degree of airway compression and second to assess the response to anti-tuberculous therapy. A number of commentators recommend rapid initiation of steroid therapy, and this would seem sensible prior to progression to CT scanning. Broad-spectrum antibiotics Broad-spectrum antibiotics is incorrect. This gentleman is already on antibiotic treatment for his tuberculosis and his current symptoms are a consequence of enlarged mediastinal nodes secondary to his tuberculosis. There is no need for additional antibiotics. Ethambutol Ethambutol is incorrect. As this gentleman started his antibiotic treatment for his tuberculosis 3 weeks ago he should already be taking ethambutol. Heparin Heparin is incorrect. Heparin would be an appropriate therapy for a pulmonary embolus. This gentleman’s dyspnoea has a clear explanation (extrinsic compression of carina) and so treatment for pulmonary embolus would be inappropriate. Tracheostomy Tracheostomy is incorrect. The gentleman is stated as being alert, orientated and maintaining his oxygenation, therefore there is time to proceed with furtherinvestigation with CT scanning before deciding on definitive management.

Question 895

Topic: 1. General Principles & Basic Science
Which of the following relates to an exacerbation of chronic bronchitis in patients with chronic obstructive pulmonary disease?
. An elevated white cell count indicates exacerbation
. Clinical symptoms are always severe
. Gram staining is inconclusive and blood cultures are necessary
. Moraxella catarrhalis is commonly a cause of COPD exacerbation
. Trimethoprim/sulfamethoxazole combinations are effective in the treatment of M. catarrhalis infection

Correct Answer & Explanation

. Moraxella catarrhalis is commonly a cause of COPD exacerbation

Explanation

Moraxella catarrhalis is commonly a cause of COPD exacerbation. Along with Haemophilus influenzae and Streptococcus pneumoniae, M. catarrhalis is a common cause of exacerbations of chronic bronchitis and pneumonia in patients with COPD. Symptoms of Moraxella infection tend to be mild to moderate in severity and it is quite common for the white cell count not to be raised.

Question 896

Topic: 1. General Principles & Basic Science

A 41-year-old woman presents to the Emergency Department with sudden onset of pleuritic chest pain and breathlessness. A chest X-ray reveals a large right-sided pneumothorax. Pleural aspiration fails to result in adequate re-expansion of the lung and you therefore insert an intercostal tube connected to an underwater seal. After 24 hours of intercostal drainage the lung has not re- expanded despite the fact that the drain is still swinging with respiration. What would you do next?

. High-volume/low-pressure suction should be used
. Negative suction should be started at -1 to -2 cm H2O
. Refer for immediate surgical intervention
. Reposition the chest drain
. Wait another 24 hours

Correct Answer & Explanation

. Wait another 24 hours

Explanation

Correct Answer: E- Wait another 24 hours Explanation Wait another 24 hours If pneumothorax fails to re-expand or if there is a persistent air leak (bubbling present) after 48 hours, then you should refer the patient to a respiratory specialist because negative suction might be required. The normal intrapleural pressure is -3.4 cm H2O during expiration, rising to -8 cm H2O during inspiration. High- volume/low-pressure suction should be considered if there is a persistent air leak and/or full lung re-expansion has not occurred approximately 48 hours following chest drain insertion. High-volume/low-pressure suction should be used High-volume/low-pressure suction should be used is incorrect. If high-volume/high-pressure suction is used, then high-airflow suction might be generated, which can lead to air stealing, hypoxaemia and/or the persistence of air leaks. Negative suction should be started at -1 to -2 cm H2O Negative suction should be started at -1 to -2 cm H2O is incorrect. Negative suction should be started at -10 to -20 cm H2O (-1 to -2 kPa = -7.5 to -15 mmHg) using a high- volume/low-pressure suction system. Refer for immediate surgical intervention Refer for immediate surgical intervention is incorrect. If appropriate suction fails to result in adequate re- expansion by 3–5 days then referral to a thoracic surgeon is indicated. Reposition the chest drain Reposition the chest drain is incorrect. The drain is still swinging with respiration, indicating it is still within the pleural cavity and therefore there is no need to reposition the drain at this stage.

Question 897

Topic: 1. General Principles & Basic Science
A 62-year-old man who is a current smoker has been followed up for breathlessness with productive cough. Five years ago his FEV1/FVC was 80%, but this ratio is now only 50%. Which of the following treatments would have the biggest clinical impact?
. Inhaled anticholinergics
. Inhaled steroids
. Salbutamol
. Short course of prednisolone
. Smoking cessation

Correct Answer & Explanation

. Smoking cessation

Explanation

Smoking cessation is the correct answer. This man has severe COPD and has deteriorated significantly during the past 5 years. Currently, the only interventions that have been proven to affect mortality are smoking cessation and long-term oxygen therapy (in patients who meet the prescription criteria).

Question 898

Topic: 1. General Principles & Basic Science

A 46-year-old man with a history of asthma, well controlled with regular low-dose Seretide, presents with a cough productive of purulent, blood-stained sputum. On examination his temperature is 38.6 °C, pulse is 90/min and regular; there is a cluster of cold sores on his upper lip. Auscultation reveals left-sided consolidation. Which of the following causes of lower respiratory tract infection is most likely to be associated with herpes labialis?

. Haemophilus influenzae
. Mycoplasma pneumoniae
. Staphylococcus aureus
. Streptococcus pneumoniae
. Streptococcus pyogenes

Correct Answer & Explanation

. Streptococcus pneumoniae

Explanation

Correct Answer: D- Streptococcus pneumoniae Explanation Streptococcus pneumoniae Streptococcus pneumoniae is a common cause of community-acquired pneumonia and is characteristically associated with herpes labialis. In this case the majority of standard hospital protocols recommend dual therapy with a combination of co- amoxiclav and clarithromycin as the intervention of choice. Haemophilus influenzae Haemophilus influenzae is incorrect. Haemophilus influenzae is seen more frequently in patients with chronic obstructive pulmonary disease (COPD). Mycoplasma pneumoniae Mycoplasma pneumoniae is incorrect. Mycoplasma is a cause of atypical pneumonia. Staphylococcus aureus Staphylococcus aureus is incorrect. Staphylococcus aureus pneumonia is more likely to follow a viral respiratory tract infection such as influenza, and we are given no history of a prodromal viral illness here. Streptococcus pyogenes Streptococcus pyogenes is incorrect. Streptococcus pyogenes is most commonly associated with head and neck infections, eg pharyngitis, and skin and soft tissue infections, eg cellulitis.

Question 899

Topic: 1. General Principles & Basic Science
A 49-year-old homosexual accountant came to the clinic with increased breathlessness. He had begun to become wheezy after a tooth extraction procedure 5 months ago and also had an associated troublesome cough. He used to smoke 15 cigarettes per day but gave up smoking about 2 months ago. Salbutamol and beclometasone inhalers only poorly controlled his symptoms. Recently he had been unwell: he had had a fever and had lost about 3.2 kg (7 lb) in weight. There was no history of recent foreign travel and no significant past illness. On examination, he had a temperature of 37.2 °C and occasional rhonchi on both sides. Tests showed: haemoglobin 14.6 g/dl, white cell count 10.2 × 10^9/l (neutrophils 53%, lymphocytes 30%, raised eosinophils noted), ESR 110 mm in 1st hour; normal U&Es, normal urine dipstick. A chest X-ray showed extensive symmetrical, homogenous shadowing affecting all the peripheral lung field. A skin test for inhaled antigens, including Aspergillus fumigatus, was negative. His serum IgE was normal. A serological screen for parasitic infection was negative. Pulmonary function was within normal limits. Oxygen saturations were 97% and there was no desaturation on exercise. What is the probable diagnosis?
. Asthma
. Cryptogenic pulmonary eosinophilia
. Granulomatosis with polyangiitis
. Loeffler syndrome
. Pneumocystis pneumonia

Correct Answer & Explanation

. Cryptogenic pulmonary eosinophilia

Explanation

This patient has eosinophilia and associated pulmonary signs, but no indications of drug involvement or malignancy. He has cryptogenic pulmonary eosinophilia. Systemic features can occur in this condition, including: malaise, weight loss, fever, raised ESR, and asthma (in around 50%). The disease responds to steroid treatment.

Question 900

Topic: 1. General Principles & Basic Science

You are asked to see a 32-year-old immigrant who complains of chronic cough and weight loss over the past few months. Examination of sputum reveals acid- and alcohol-fast bacilli (AAFB) and tuberculosis is confirmed. You elect to begin treatment with isoniazid, rifampicin, ethambutol and pyrazinamide as he is from an area where high levels of drug resistance are present. Which of the following blood tests is most desirable before starting therapy?

. Clotting screen
. Haemoglobin
. Liver function testing
. Platelet count
. Serum calcium

Correct Answer & Explanation

. Liver function testing

Explanation

Correct Answer: C- Liver function testing Explanation Liver function testing This is a ‘know it or you don’t’ question. Both isoniazid and rifampicin can be associated with significant hepatic dysfunction. In particular, severe and sometimes fatal hepatitis has been seen with isoniazid. Particular problems occur in slow acetylators, who can have markedly elevated serum isoniazid levels. In patients with existing liver dysfunction, rifampicin and isoniazid should only be used in cases of absolute clinical necessity. Even then, dose reduction of rifampicin is recommended and initial weekly monitoring of liver function tests should be carried out. Clotting screen Clotting screen is incorrect. Clotting screen is not as important as liver function testing in this instance. Haemoglobin Haemoglobin is incorrect. Haemoglobin testing is not as important as liver function testing in this patient. Platelet count Platelet count is incorrect. Platelet count is not as important as liver function testing in this patient. Serum calcium Serum calcium is incorrect. Serum calcium is not as important as liver function testing in this patient.

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