Case-based MCQ

🇨🇦 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

🇨🇦 MCCQE1,2 | #Case_78 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 44-year-old black female has right upper quadrant abdominal pain that began as a sharp stabbing pain the night before. It has continued as a dull ache with brief periods of relief. She has experienced nausea the last 3 days without any change in bowel habits. There is no history of trauma. A medical and surgical history reveals nothing significant. On examination you note an obese female in mild distress. Her temperature is 38.3°C (101.0°F), her heart rate 96 beats/min, respirations 18/min, and blood pressure 122/84 mm Hg. The lungs are clear, and the heart is normal. She is not jaundiced. There is mild diffuse tenderness to palpation in the right upper quadrant with minimal guarding and no rebound tenderness. Ultrasonography of the right upper quadrant is nondiagnostic.Which one of the following diagnostic tests would be lmost useful for demonstrating an obstruction? a) Endoscopic retrograde cholangiopancreatography (ERCP) b) Colonoscopy c) A ventilation-perfusion lung scan d) Cholescintigraphy (HIDA scan) e) CT scan

🇨🇦 MCCQE1,2 | #Case_77 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Congenital diaphragmatic hernia is often seen on prenatal ultrasound. A diaphragmatic hernia is a defect in the hemidiaphragm that allows the abdominal contents into the thorax. It has the findings of respiratory distress, cyanosis, and scaphoid abdomen. Auscultation will show decreased breath sounds on the affected side. It occurs more often on the left side than the right.

🇨🇦 MCCQE1,2 | #Case_77 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 An infant is delivered at full term by a spontaneous vaginal delivery to a 30-year-old primigravida. At delivery, the infant is noted to have subcostal retractions and cyanosis despite good respiratory effort. The abdomen is scaphoid. On bag and mask ventilation, auscultation of the lungs reveals decreased breath sounds on the left, with heart sounds louder on the right. Which of the following is the most likely diagnosis? a) Dextrocardia with situs inversus b) Diaphragmatic hernia c) Pneumonia d) Pulmonary hypoplasia e) Spontaneous pneumothorax

🇨🇦 MCCQE1,2 | #Case_76 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation Autism is a pervasive condition affecting 7 out of 10,000 persons. Defined behaviorally as a syndrome consisting of abnormal development of social skills, sensorimotor deficits, and limitations in the use of interactive language, it is characterized by variable development, resulting in good skills in some areas and poor skills in others. No single cause has been linked to the development of autism. Studies have failed to show an association between any vaccine and the disorder. To date, no biologic markers are available to aid in the identification of patients with autism. Successful programs in the treatment of autism include behavioral modification strategies as well as programs emphasizing the development of social communication and early, active, and consistent family participation.

🇨🇦 MCCQE1,2 | #Case_76 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 For several months you have been evaluating a 2 1/2 year old male whose parents have numerous concerns. The patient has extreme difficulty mixing with other children, preferring to be alone. He is quite aloof around others, gesturing or pointing instead of using words. He also throws extreme tantrums for no apparent reason. The child does not respond to regular verbal cues and often simply ignores others when spoken to. His vocabulary is less than 10 words and he has never put two words together. Hearing screening tests and an EEG are normal.Which one of the following is true regarding this patient’s disorder? a) Pathologic parenting is most likely responsible for this etiology b) Immunizations, particularly MMR, may precipitate the disorder c) Biologic markers are useful for making the diagnosis d) The development of specific impairments is varied and unpredictable e) Behavioral modification programs are not helpful

🇨🇦 MCCQE1,2 | #Case_75 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation The development of hematoma after a thyroidectomy is a rare complication of the surgical procedure. Typically, a cervical hematoma is large, tense, firm, immobile anterior cervical swelling under the incision, which can be accompanied by respiratory distress and stridor. This complication presents in as much as 1.2 percent of patients post thyroidectomy. Once the diagnosis is suspected, the patient should be taken to the OR for exploration of the incision. There is no recommended diagnostic study or procedure prior to opening of the incision as it is an emergency. Also, the patient should be kept awake in order to allow airway protection. Once the incision is open, the blood can be evacuated, making intubation easier. ⚠ It would be inappropriate to waste time in obtaining an X-ray (choice A) or a CT scan (choice B). ⚠ Intubation (choice C) should not precede the exploration of the incision, nor should laryngoscopy (choice E). ✅Key point: Although rare, a hematoma after a thyroidectomy is a life threatening complication. It is vital to know that exploration of the wound should precede any other study or procedure.

🇨🇦 MCCQE1,2 | #Case_75 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 34-year-old woman underwent an uneventful subtotal thyroidectomy for Grave's disease. A few hours later, you are called by the nurse because the patient is complaining of difficulty breathing. When you see the patient you find her distressed and you can hear inspiratory stridor. There is a large, firm, tense, anterior swelling right under the surgical wound. What is the most appropriate next step in the management? a) Neck X-ray b) Neck CT scan c) Intubation d) Opening the incision in the OR e) Laringoscopy

🇨🇦 MCCQE1,2 | #Case_74 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation This patient has epididymo-orchitis. This condition is most often caused by coliform bacteria in men over the age of 35 (and in homosexual males). These organisms are effectively treated with ofloxacin. Those less than age 35 with this condition have a higher chance of having a sexually transmitted disease (STD) and would benefit from intramuscular ceftriaxone and oral doxycycline. However, these medications would not adequately cover coliform bacteria. Clindamycin and famciclovir would also be ineffective. Testicular torsion is another possible cause of testicular pain with a quick onset, and would require urgent urologic surgery consultation. However, in cases of torsion the examination usually reveals an elevated testicle and testicular ultrasonography would show decreased or absent blood flow on the affected side.

🇨🇦 MCCQE1,2 | #Case_74 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 50-year-old married male comes to your clinic complaining of right testicular pain that developed quickly over the last 24 hours. He reports no fever, dysuria, or urethral discharge. He is nauseous but has no emesis or diarrhea. His abdominal examination is benign but he has an enlarged, exquisitely tender right hemi-scrotum. A urinalysis is normal and his WBC count is 13 x 10^9/L. Testicular ultrasonography shows increased blood flow in the affected testicle and epididymis. Which one of the following would be the best treatment for this patient’s condition? a) Ceftriaxone (Rocephin), 250 mg intramuscularly once, plus doxycycline, 100 mg orally twice daily for 10 days, and treatment of all sexual partners b) Clindamycin (Cleocin), 300 mg orally 4 times daily for 7 days c) Famciclovir (Famvir), 250 mg orally 3 times daily for 7 days d) Ofloxacin (Floxin), 300 mg orally twice daily for 10-14 days e) Urgent urologic surgery consultation

🇨🇦 MCCQE1,2 | #Case_73 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ D 🔎 Explanation A perilymphatic fistula (choice D) between the middle and inner ear may be caused by barotrauma from scuba diving, as well as by direct blows, heavy weight bearing, and excessive straining (e.g., with sneezing or bowel movements.) This patient’s recent trip involved two of these potential factors. Most patients with fistulas find that their symptoms get worse with changes in altitude (elevators, airplanes, travel over mountain passes) or air pressure (weather changes). ⚠ Vestibular neuronitis (choice A) is a more sudden, unremitting syndrome. ⚠ Meniere’s disease (choice B) is manifested by episodes of vertigo, associated with hearing loss and often with nausea and vomiting. ⚠ Benign paroxysmal positional vertigo (choice C) is more likely in older individuals, and is associated with postural change. ⚠ Multiple sclerosis (choice E) requires symptoms in multiple areas and is not thought to be provoked by climate change.

🇨🇦 MCCQE1,2 | #Case_73 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 42-year-old African-Canadian male recently traveled to the Caribbean for a scuba diving trip. Since his return he has noted brief intermittent episodes of vertigo not associated with nausea or vomiting. He is concerned, however, because these episodes occurred after sneezing or coughing and then a couple of times after straining while lifting something. He has had no hearing loss, and no vertigo with positional changes such as bending over or turning over in bed. He does mention that it gets worse when he's taking the elevator. The most likely cause of this patient’s vertigo is: a) Vestibular neuronitis b) Meniere’s disease c) Benign paroxysmal positional vertigo d) A perilymphatic fistula e) Multiple sclerosis triggered by a rapid change in climate

🇨🇦 MCCQE1,2 | #Case_72 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ B 🔎 Explanation A subacute onset of fever with rigors and chills, non-productive cough, shortness of breath and pleuritic chest pain with findings of right middle lobe consolidation are consistent with community acquired pneumonia (CAP) (choice B). However, presence of erythema multiforme, low hemoglobin, agglutination on peripheral blood smear and hyponatremia point towards the diagnosis of (CAP) most likely due to mycoplasma pneumonia. Low hemoglobin is due to autoimmune hemolytic anemia due to formation of cold agglutinins. Whereas hyponatremia is due to syndrome of inappropriate ADH (SIADH) secretion associated with mycoplasma pneumomiae Community acquired pneumonia (CAP) is diagnosed outside of the hospital in ambulatory patients who are not residents of nursing homes or other long-term care facility. It may also be diagnosed in a previously ambulatory patients within 48 hours after admission. Most patients with CAP experience an acute or subacute onset of fever, cough with or without sputum production and dyspnea. Other common symptoms include night sweats, chills, rigors, chest discomfort, pleurisy, hemoptysis, fatigue, myalgias, anorexia, headache, and abdominal pain. Common physical findings include fever, tachypnea, tachycardia, and arterial oxygen desaturation. Chest examination often reveals inspiratory crackles and bronchial breath sounds with a dull percussion note. The clinical evaluation is < 50% sensitive compared to chest imaging for the diagnosis of CAP. In most patients, therefore, a chest radiograph is essential to the evaluation of CAP. ⚠ Legionnaires disease (choice A) is caused by Legionella pneumophila and is responsible for causing atypical pneumonias in both immunocompetent and immunocompromised individuals. Although the clinical picture mimics one of Legionnaires disease, lack of history of exposure to hot water tanks, cooling towers, and evaporative condensers of large air conditioning systems, such as those commonly found in hotels and large office buildings, makes it less likely to be the cause of this patient's disease. ⚠ Aspergilloma (choice C) is caused by Aspergillus fumigatus, a fungus. Upper lobes are frequently involved and fungal balls readily form in tuberculous cavities. Patients are usually asymptomatic with tumor-like opacity on chest X-ray. ⚠ Suppurative pneumonia (choice D) is characterized by cough with large amounts of sputum, sometimes fetid and blood stained. Moreover, there is high remittent pyrexia, digital clubbing (10 to 14 days) and presence of pleural rub in addition to the signs of consolidation in the chest X-ray. ⚠ Healthcare-associated pneumonia (choice E) is the development of pneumonia in a person who has spent at least 2 days in hospital with the last 90 days, or has attended hemodialysis unit, received intravenous antibiotics, or been a resident of a nursing home or other long-term care facility. As there is no such history, therefore health care associated pneumonia is less likely. ✅Key point: Community acquired pneumonia caused by Mycoplasma pneumoniae is one of the forms of atypical pneumonia characterized by erythema multiforme, hemolytic anemia and hyponatremia in addition to presentation of typical pneumonia.

🇨🇦 MCCQE1,2 | #Case_72 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 36-year-old female, housewife, got admitted with a six day history of fever with rigors and chills, non-productive cough, pleuritic chest pain on the right side, and increased shortness of breath. While examining her, she was found to be febrile with a temperature of 37.8°C, O2 sats were 89% on air and examination of chest revealed dull percussion note in right middle chest with inspiratory crackles and bronchial breath sounds. Moreover, she had a rash on the face, arms and legs resembling the rash of erythema multiforme. Investigations carried out were: Hemoglobin: 85 g/L White blood cell count: 6 x 109/L Platelets: 140 x 109/L Sodium: 126 mmol/l AST: 65 U/l ALT: 79 U/l Albumin: 36 g/l Peripheral blood film showed red cell agglutination Which of the following diagnosis is most consistent with the clinical picture described above? a) Legionnaires disease b) Community acquired pneumonia c) Aspergilloma d) Suppurative pneumonia e) Healthcare-associated pneumonia

🇨🇦 MCCQE1,2 | #Case_71 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Platelets are acute phase reactants and their number increases with infections and other inflammatory conditions (reactive thrombocytosis). As reported by Andrew and Schafer, only 8 out of 10,000 patients with incidental thrombocytosis were found to have high platelet counts a few weeks later. Therefore, given this patient's clinical scenario (incidental finding), platelet count should be repeated a few weeks later (choice E). ⚠ Bone marrow biopsy to rule out essential thrombocytosis (choice A) should be done only after reactive thrombocytosis is excluded. ⚠ There is no clear indication for lymph node biopsy (choice B) in this patient. The tender anterior cervical lymphadenopathy is most likely due to streptococcal pharyngitis and will usually subside in a few weeks. In addition, our patient did not have symptoms, signs or lab results suggestive of diseases associated with lymphadenopathy and thrombocytosis like myeloproliferative diseases. ⚠ Platelet retention test (choice C) is used to evaluate adhesiveness of platelets, which is known to be reduced in some diseases like Von Willebrand disease, uremia and thrombocytosis that accompany myeloproliferative diseases. Our patient, however, did not have any symptoms or signs suggestive of any of these diseases. Ruling out of reactive thrombocytosis is the priority in this patient. ⚠ Platelet release reaction (choice D) is used to evaluate ability of platelets to release their granules when activated. When platelets fail to release their granules, primary hemostasis is impaired and bleeding tendency might result. Our patient did not have bleeding tendency to suggest such an abnormality and ruling out reactive thrombocytosis is the priority in this patient. ✅Key point: Like ESR and CRP, platelets are acute phase reactants and platelet count can increase in response to infection. In presence of infection, reactive thrombocytosis should be excluded by repeating platelet count in four to six weeks before proceeding to any further investigation

🇨🇦 MCCQE1,2 | #Case_71 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 A 7-year-old girl presented with fever, sore throat and tender anterior lymphadenopathy. With appropriate work-up, the diagnosis of streptococcal pharyngitis was established. Because she had two attacks of otitis media in the past year, complete blood count (CBC) was performed. The only positive findings in the CBC were as follows: white cell count of 12.5 x 109/L, platelet count of 650 x 109/L and an erythrocyte sedimentation rate of 19 mm/hour. She was prescribed amoxicillin 40mg/kg. Regarding this patient's thrombocytosis, which of the following is the most appropriate next step in management? a) Order bone marrow biopsy b) Order lymph node biopsy c) Order platelet retention test d) Order platelet release reaction e) Repeat platelet count in four weeks

🇨🇦 MCCQE1,2 | #Case_70 | #answer 〰〰〰〰〰〰〰〰〰〰〰〰〰〰 ✅ E 🔎 Explanation Vertigo, the sense of movement of oneself or the environment or simple feeling of spinning, is caused by lesions of the peripheral (located in the bony labyrinth) or central components of the vestibular system (located in spinal cord, brain stem, cerebral cortex and cerebellum). Vertigo can be physiological and examples of this include vertigo with extreme head extension, height vertigo or vertigo following a spin. Pathological causes include benign paroxysmal positional vertigo, Meniere’s disease, vestibular neuritis, acoustic neuroma or vascular lesions of the above brain areas. Normally, projections from the peripheral components of the vestibular system to the cerebral cortex make us conscious of our head position and movement, projections to spinal cord helps us maintain postural stability and projections to the cerebellum modulate the vestibuloocular reflex (VOR) that controls visual stability during head movement. The efferent limb of the VOR is carried through the 3rd, 4th and 6th cranial nerves and is normal in peripheral lesions of the vestibular system. Thus, disappearance of nystagmus during visual fixation (choice E) is typical of nystagmus accompanying vertigo caused by peripheral lesions (Labyrinth lesions). Nystagmus accompanying vertigo caused by central lesions (lesions of brain stem or cerebellum) usually persists during visual fixation due to disruption of this efferent limb of the VOR. ⚠ Vertigo may be of acute onset (choice A) in both peripheral and central lesions. Whether onset is acute or chronic depends on the cause rather than site of lesion. Ischemia of the labyrinth (peripheral) or the brain stem or cerebellum (central) can lead to abrupt onset of vertigo. ⚠ Mild nature of vertigo (choice B) favours central rather than peripheral causes of vertigo. Vertigo due to peripheral causes is usually severe. ⚠ Absence of tinnitus (choice C) favours central rather than peripheral causes of vertigo. Vertigo is usually not accompanied by tinnitus when caused by central lesions. ⚠ Unidirectional nystagmus (choice D) can be associated with both central and peripheral causes of nystagmus. ✅Key point: Simple bedside tests can help differentiate between central and peripheral causes of nystagmus. For example, nystagmus that persists during visual fixation favours central over peripheral causes of vertigo.