Case-based MCQ

🇨🇦 MCCQE1,2 | #Case_88 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 74-year-old man presents to his primary care physician complaining of dyspnea and cough with blood-tinged sputum for the past several weeks. He has diabetes and elevated cholesterol. Medications include a sulfonylurea and a statin. The patient has a 50 pack-year smoking history and a family history of hypertension. On examination, vital signs are withinnormal limits; abdominal striae and moon facies are noted, along with a trucal fat distribution. X-ray of the chest reveals a single central nodule, and follow-up CT again demonstrates the nodule and multiple solid hepatic masses. Which of the following is the most likely diagnosis? a) Adenocarcinoma of the lung b) Carcinoma metastatic to the lung c) Large cell carcinoma of the lung d) Small cell carcinoma of the lung e) Squamous cell carcinoma of the lung

🇨🇦 MCCQE1,2 | #Case_87 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation The child is presenting with symptoms of Reye syndrome, which is an acute encephalopathy associated with high ammonia levels. It most commonly occurs in young children after a viral illness. Administration of aspirin increases the risk of developing this disorder. The vomiting is characteristic.

🇨🇦 MCCQE1,2 | #Case_87 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 4-year-old boy develops a headache, cough, myalgia and a fever. He has been a healthy child with all immunizations up to date. He is given a decongestant and an aspirin for his symptoms with some relief. However, 3 days later, he is brought back by his parents because of persistent vomiting and irritability. On physical examination, he is found to be semicomatose, becoming combative on stimulation. Which of the following levels should be measured to aid in the diagnosis of this patient? a) Serum ammonia level b) Serum blood urea nitrogen level c) Serum calcium level d) Serum opiate level e) Serum sodium level

🇨🇦 MCCQE1,2 | #Case_86 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation This patient most likely experienced a simple febrile seizure. Most febrile seizures last less than 10 minutes, are generalized and nonfocal, and do not recur within 24 hours. These simple febrile seizures do not require evaluation beyond determining and treating the source of the fever and educating parents. ⚠ There is no need for neuroimaging studies in a case of simple febrile seizure. ⚠ There is no need for an EEG in the case of a simple febrile seizure with a negative family history, normal neurologic exam, and normal development. ⚠ Although anticonvulsant medications are sometimes used for recurrent episodes of febrile seizures, the initial simple febrile seizure does not warrant treatment with anticonvulsant drugs. ⚠ A lumbar puncture is not indicated in this patient unless the physical exam revealed symptoms suggestive of meningitis or encephalitis. In this case, the examination is normal except for the otitis media, the source of the fever.

🇨🇦 MCCQE1,2 | #Case_86 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 2-year-old boy presents to the emergency department for evaluation following a witnessed seizure. The seizure was described as generalized, lasting less than 10 minutes with a short postictal period. The child has no history of seizures, no family history of seizures, and no history of head injury. His exam currently is normal, except for a red, bulging right tympanic membrane and a temperature of 39°C. What is the most appropriate management for this patient? a) He should be sent for an urgent CT scan of the head b) He should be given antibiotics and antipyretics and observed at home c) He should be admitted to the hospital and an EEG should be performed d) He should be started on phenobarbital and sent home e) A lumbar puncture and blood cultures should be obtained and anticonvulsants started in the hospital

🇨🇦 MCCQE1,2 | #Case_85 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Tics are abnormal movements or vocalizations involving one or more muscles; resulting in blinking of eye, nose sniffing, coughing, neck twitching or jerking, abnormal phonation, and jerking of limbs. Unlike seizures, the tics are suppressible for some time with conscious effort. When both motor and phonic tics are present for more than a year, as in this patient, the condition is described as Tourette syndrome (TS).TS is a genetic neurological condition and is often associated with attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). Over half of the patients with TS also have significant obsessive-compulsive symptoms, and approximately 30% meet the diagnostic criteria for OCD (choice D). The pattern of co-morbidity indicates that the TS gene may be responsible for a spectrum of disorders, including OCD and ADHD. ⚠ Autism (choice A) is a neuro-developmental disorder of impaired social interaction and communication, and of restricted and repetitive behavior. The movements in autism are purposeful and repetitive unlike in TS. ⚠ Bipolar disorder (choice B), also known as manic-depressive disorder, is a mood disorder characterized by changes in mood, energy and activity levels affecting ability to carry out daily tasks. It is not known to be present with TS. ⚠ Chorea (choice C) is a state of excessive, spontaneous movements, irregular, non-repetitive, randomly distributed and abrupt in character. TS does not have an association with chorea. ⚠ Schizophrenia (choice E) is a thought disorder characterized by abnormal social behavior due to failure to recognize what is real. Thought is not affected in TS and TS is not associated with schizophrenia. 🔖 Key point: In Tourette syndrome, trying to suppress the tics produce anxiety and tension that can only be relieved by allowing the tics to occur, whereas In OCD, the repetitive compulsive behaviors are performed to relieve anxiety caused by an obsession. Neuroimaging studies suggest that both disorders involve defect in the basal-ganglia thalamo-cortical pathways, explaining the co-morbidity.

🇨🇦 MCCQE1,2 | #Case_85 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 15-year-old boy is brought by his parents with a complaint of involuntary excessive blinking and twitching of hand muscles that has increased in frequency in the last 2 months and is interfering with preparation for his exams. Involuntary blinking (almost daily) and occasional repetitive vocalizations have been present since he was seven years old. He can suppress the movements sometimes if he tries hard. The episodes are not associated with loss of consciousness.Electroencephalography is normal.Which one of the following conditions is the most common comorbidity associated with the disorder? a) Autism b) Bipolar disorder c) Chorea d) Obsessive compulsive disorder e) Schizophrenia

🇨🇦 MCCQE1,2 | #Case_84 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation The first rule of thumb in your clinical practice: DO NOT HARM! A solid mass arising from the testicle in a young adult is likely to be malignant! Surgical referral for high inguinal orchiectomy should be warranted. A biopsy of a suspicious mass of the testicle is contraindicated because it can result in spillage of cancer cells, which can spread through lymphatics and blood vessels.Reassurance or follow up in a case suspected to have cancer is never appropriate.Never take biopsy from a suspicious solid testicular mass!

🇨🇦 MCCQE1,2 | #Case_84 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 25 year old male patient presents to your clinic complaining of heaviness in his scrotum. His past medical history is unremarkable. He does not smoke or drink alcohol. His family history is noncontributory. Physical exam is normal except for a painless, hard mass in his right testicle.You order a testicular ultrasound which reveals a solid mass arising from the right testicle 2x2 cm. What should you do next? a) Fine needle aspiration b) Reassurance c) Repeat the ultrasound after 6 months d) Surgery e) Trans-scrotal biopsy

🇨🇦 MCCQE1,2 | #Case_83 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation Guidelines have been established for the management of anticoagulation during invasive procedures. Patients with lone atrial fibrillation without previous thromboembolic events are at low risk (<1% annualized thrombotic risk) for a thrombotic event in the absence of anticoagulation. They can be safely managed with cessation of warfarin 3-4 days preoperatively, and resumption of warfarin postoperatively when the surgeon indicates it is safe to do so. If the operative procedure is associated with a high risk of thrombosis, then prophylactic, rather than therapeutic, doses of unfractionated or low-molecular-weight heparin can be used as a postoperative bridge to restarting warfarin. Patients at high risk for a thrombotic event in the absence of anticoagulation, such as those with prosthetic heart valves, should be managed by stopping warfarin 3-4 days preoperatively, beginning fully therapeutic doses of low-molecular weight heparin or intravenous unfractionated heparin when the INR decreases below the therapeutic range, stopping therapy briefly for surgery, and then resuming the heparin bridge postoperatively until warfarin is resumed. Dental procedures do not generally require interruption of anticoagulation therapy with warfarin.

🇨🇦 MCCQE1,2 | #Case_83 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 73-year-old black male being treated with warfarin (Coumadin) for chronic atrial fibrillation has been scheduled by his podiatrist for a bunionectomy. He has no history of a previous thromboembolic event, and his most recent INR was 2.5. The patient consults you regarding the preoperative and postoperative management of his anticoagulation.You plan to stop his regular daily warfarin dose 3-4 days prior to his scheduled operation and restart it the day after. Which one of the following would be most appropriate during the 4-5 days he is not taking his regular warfarin? a) No additional medication b) Aspirin, 81-325 mg/day orally c) Half of his usual daily warfarin dose d) Low-molecular-weight heparin injections once or twice a day e) Admission to the hospital for treatment with intravenous heparin

🇨🇦 MCCQE1,2 | #Case_82 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Leukoplakia is a white keratotic lesion seen on mucous membranes. Irritation from various mechanical and chemical stimuli, including alcohol, favors development of the lesion. A definitive diagnosis of leukoplakia is made when any aetiological cause, e.g. tobacco, C. albicans, mechanical irritation, has been excluded and histopathologic examination (choice E) has not disclosed any other specific disorder. Leukoplakia can occur in any area of the mouth and usually exhibits benign hyperkeratosis on biopsy. ⚠ On long-term follow-up (choice A), 2%-6% of these lesions will have undergone malignant transformation into squamous cell carcinoma. ⚠ An idiosyncratic reaction to propranolol (choice B) is unlikely in this patient. ⚠ Oral nystatin (choice C) would not be appropriate treatment, as this lesion is not typical of oral candidiasis. Candidal lesions are usually multiple and spread quickly when left untreated. ⚠ A fluorescent antinuclear antibody test (choice D) is also not indicated, as the oral lesions of lupus erythematosus are typically irregular, erosive, and necrotic

🇨🇦 MCCQE1,2 | #Case_82 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 45-year-old white male consults you because of a painless, circular, 1-cm white spot inside his mouth, which he noticed 3 days ago. You are treating him with propranolol for hypertension, and you know him to be a heavy alcohol user. After a careful physical examination, your tentative diagnosis is leukoplakia of the buccal mucosa. You elect to observe the lesion at that time. On the patient’s return, the lesion is still present and unchanged in appearance. The best course of management at this time is to: a) reassure the patient and continue to observe b) discontinue propranolol c) treat with oral nystatin d) order a fluorescent antinuclear antibody test e) perform a biopsy of the lesion

🇨🇦 MCCQE1,2 | #Case_81 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Erysipelas, most commonly caused by group A beta-hemolytic Streptococci, is the most likely diagnosis of this patient. The characteristic finding of erysipelas is a sharply demarcated, erythematous, edematous tender skin lesion with raised borders. It is frequently seen in diabetics where a tinea pedis infection is the usual portal of entry of the infection.Staphylococcus aureus is a rare cause of erysipelas. Remember that staph aureus are coagulase positive organisms that secrete coagulase enzyme which limits the spread of the infection in the dermis. Dermatophytes are the cause of the toe web infection and not the erysipelas. Actinomyces israelii is the causative agent of cervicofacial infections characterized by the sinuses discharging sulphur granules.Clostridium perfringens is the causative agent of gas gangrene

🇨🇦 MCCQE1,2 | #Case_81 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 60-year-old diabetic male presents to the ED with fever and painful swelling of his right leg that began few hours ago. He is taking metformin and glyburide for his diabetes since he was diagnosed 5 years ago and admits to medication non-compliance. Vital signs are within normal limits except for a fever of 39°C. Examination of the leg shows raised borders of a well-demarcated area of erythema that is warm and extremely painful to touch. Cracks in the skin of the toe webs are noted on the examination of his feet. Which of the following is the most likely causative organism for the patient’s condition? a) Actinomyces israeili b) Clostridium perfringens c) Dermatophytes d) Staphylococcus aureus e) Streptococcus pyogenes (group A)

🇨🇦 MCCQE1,2 | #Case_80 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ A 🔎 Explanation Aldosterone, a hormone produced and secreted by the adrenal glands, signals the kidneys to excrete less sodium and more potassium. Hyperaldosteronism can be caused by a tumor (usually a noncancerous adenoma) in the adrenal gland (a condition called Conn's syndrome), although sometimes both glands are involved and are overactive. Sometimes hyperaldosteronism is a response to certain diseases, such as very high blood pressure (hypertension) or narrowing of one of the arteries to the kidneys.The amount of salt in the diet and medications, such as over-the-counter pain relievers of the non-steroid class (such as Motrin and Advil), diuretics (water pills), beta blockers, steroids,angiotensin-converting enzyme (ACE) inhibitors, and oral contraceptives can affect the test results. You should ask your patient to stop taking some of his medicines for 2 weeks before the test. ✅ Screening test: Random plasma aldosterone/plasma renin activity (PRA) ratio - Because this ratio is fairly constant over many physiologic conditions, it can be used as a screening test. Normal values are less than 270 when aldosterone concentration is expressed in pmol/L, or are less than 10 when aldosterone concentration is expressed in ng/dL. ✅ Confirmatory test: The 24-hour urinary aldosterone (U-Aldo) excretion test is one of the most useful confirmatory diagnostic tools

🇨🇦 MCCQE1,2 | #Case_80 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 You are asked to see a 48-year-old male patient because of persistent hypertension despite taking metoprolol, enalapril and nifedipine. There is no history of palpitations or flushing, and the patient does not use any nonsteroidal anti-inflammatory drugs. Blood pressure in your office was found to be elevated at 160/110 mmHg. Recent laboratory testing shows sodium: 146 mmol/L; potassium: 2.4 mmol/L and creatinine: 85 µmol/L. There is no proteinuria on urinalysis. Which one of the following is the most appropriate test to arrange at this time? a) Random plasma aldosterone/plasma renin activity ratio b) 24-hour urine collection for catecholamines and creatinine c) 24-hour ambulatory blood pressure monitor d) 24-hour urine collection for cortisol e) Nuclear medicine captopril renal scan

🇨🇦 MCCQE1,2 | #Case_79 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation Gut-associated lymphoid tissue plays a role in HIV replication. Immune cells in the GI tract (choice B) are organized into distinct immune inductive sites, considered as sites of T cell education, and immune effector sites, where T cells neutralize foreign antigens - both microbial and nonmicrobial. Immune inductive sites are comprised of Peyer’s patches (PPs) and mesenteric lymph nodes (MLNs). Peyer’s patches have the anatomic appearance of secondary lymphoid organs, with clearly defined T- and B-cell-dependent areas. These have been shown to be the sites of early seeding and establishment of the proviral reservoir. This reservoir contributes to the difficulty of controlling the infection, and efforts to reduce the levels of HIV provirus through sustained antiretroviral therapy. ⚠ The percentage of mucosal CD4+ cells that coexpress CCR5 and CXCR4 chemokine receptors is substantially greater in the gastrointestinal tract than that seen in the blood (choice A). Although the portal of entry for HIV infection is typically through direct blood inoculation or exposure of the virus to genital mucosal surfaces, the GI tract contains a large amount of lymphoid tissue, making this an ideal site for HIV replication. HIV replicates in activated T cells and activated T cells migrate to the lymph nodes. As such, much of the viral replication occurs outside of the peripheral blood, even though serum viral load is still a useful surrogate marker of viral replication. ⚠ Exposure of the virus to genital mucosal surfaces (choice C) is a significant portal of entry for HIV, but is not the most ideal site for viral replication. ⚠ The dorsal root ganglion (choice D) is the ideal site for HSV-2. It is contracted via contact with the mucosal and abraded skin surfaces. Following contact, viral replication ensues and infection of either sensory or autonomic nerve endings may occur. Virus, or most likely the nucleocapsid, is transported intraaxonally to the nerve cell bodies in ganglia. HSV-2 prefers the sensory nerve cells in the genital region and thus lies latent in the dorsal root ganglia located in the lower part of the back. ⚠ Studies of T-cell-replication kinetics have revealed that untreated HIV infection is characterized by rapid T-cell turnover but a defect in T-cell replication from the thymus (choice E). Several of the HIV proteins directly affect T-cell function, either by disrupting cell cycling or down-regulating the CD4 molecule. Direct cytotoxic effects of viral replication are likely not the primary cause of CD4 T-cell loss; a significant bystander effect is likely secondary to T-cell apoptosis as part of immune hyperactivation in response to the chronic infection. ✅Key point: The most ideal site for HIV replication is the gastrointestinal tract.

🇨🇦 MCCQE1,2 | #Case_79 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 39-year-old homosexual man, who was diagnosed with HIV 2 years ago, presents for his annual physical exam. He currently has no complaints of any new symptoms except fatigue, which he has had for quite some time.This is how he got diagnosed 2 years ago: he had presented with a 4 day history of fever, sore throat, lymphadenopathy, and malaise. He also had a mild diffuse headache. After ruling out infectious mononucleosis and learning of the patient’s risk factors, the physician had done HIV serology that came out positive. The patient has not been on antiretroviral therapy. He has not presented with any opportunistic infection up to date. Today his temperature is 37.8°C respiratory rate 18/min, his heart rate 90/min, and his blood pressure 120/75 mmHg. WBC count: 5.3x109/L Hematocrit 0.37 Platelet count 220 x109/L CD4+ count 0.295 x109/L Serum HIV viral load 100 copies/mL It is assessed that he may still be in the asymptomatic stage of HIV infection. However, it is also noted that viral replication is clearly ongoing as his CD4+ count is declining. Which of the following is the most ideal site for HIV replication? a) Peripheral blood b) Gastrointestinal tract c) Genital mucosal surfaces d) Dorsal root ganglion e) Thymus

🇨🇦 MCCQE1,2 | #Case_78 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation This patient has signs and symptoms that are highly suggestive of gallbladder disease, specifically acute cholecystitis. Cardiac, colonic, pulmonary, and hepatic disorders can all produce a similar clinical picture, but the case as presented favors a gallbladder problem. Nuclear imaging is the most useful test for demonstrating an obstructed cystic duct, the cause for acute cholecystitis in most patients. Right upper quadrant abdominal ultrasonography may show the presence of gallstones or a thickened gallbladder wall, but these findings can occur in chronic cholecystitis and may not account for the current clinical scenario. ⚠ ERCP is not indicated until a diagnosis is established. ⚠ CT scan, colonoscopy and a ventilation-perfusion lung scan would not be beneficial unless the most likely diagnosis of gallstone cholecystitis is eliminated