Complement inhibitors — MCQs

A 36-year-old woman comes to the emergency department because of an itchy lesion on her skin. The rash developed shortly after she took an antibiotic for a urinary tract infection. Her temperature is 37.5°C (99.3°F), pulse is 99/min, and blood pressure is 100/66 mm Hg. Physical examination shows swelling of the face and raised, erythematous plaques on her trunk and extremities. Which of the following is the most likely cause of this patient's current condition?

A 15-year-old boy is admitted to the emergency department with neck stiffness, maculopapular rash, fever, and a persistent headache. A blood culture shows encapsulated gram-negative diplococci. He has had this same infection before. Which of the following proteins is likely to be deficient in this patient?

A 25-year-old woman is being evaluated due to complaint of fatigue and voiding pink urine. The laboratory results are as follows: Hb 6.7 Red blood cell count 3.0 x 1012/L Leukocyte count 5,000/mm3 Platelets 170 x 109/L Reticulocyte count 6% Hematocrit 32% The physician thinks that the patient is suffering from an acquired mutation in hematopoietic stem cells, which is confirmed by flow cytometry analysis that revealed these cells are CD 55 and CD 59 negative. However, the physician is interested in knowing the corrected reticulocyte count before starting the patient on eculizumab. What value does the physician find after calculating the corrected reticulocyte count?

A previously healthy 39-year-old man comes to the physician because of a 1-month history of fatigue and red-colored urine. His vital signs are within normal limits. Physical examination shows pallor and jaundice. His platelet count is 90,000/mm3 and creatinine concentration is 1.0 mg/dL. A direct Coombs test is negative. Flow cytometry shows erythrocytes deficient in CD55 and CD59 surface antigens. This patient is at greatest risk for which of the following complications?

A 38-year-old woman comes to the physician for a follow-up examination. Two years ago, she was diagnosed with multiple sclerosis. Three weeks ago, she was admitted and treated for right lower leg weakness with high-dose methylprednisone for 5 days. She has had 4 exacerbations over the past 6 months. Current medications include interferon beta and a multivitamin. Her temperature is 37°C (98.6°F), pulse is 90/min, and blood pressure is 116/74 mm Hg. Examination shows pallor of the right optic disk. Neurologic examination shows no focal findings. She is anxious about the number of exacerbations and repeated hospitalizations. She is counseled about the second-line treatment options available to her. She consents to treatment with natalizumab. However, she has read online about its adverse effects and is concerned. This patient is at increased risk for which of the following complications?

A 28-year-old woman has a follow-up visit with her physician. She was diagnosed with allergic rhinitis and bronchial asthma at 11 years of age. Her regular controller medications include daily high-dose inhaled corticosteroids and montelukast, but she still needs to use a rescue inhaler 3–4 times a week following exercise. She also becomes breathless with moderate exertion. After a thorough evaluation, the physician explains that her medication dosages need to be increased. She declines taking oral corticosteroids daily due to concerns about side effects. The physician prescribes omalizumab, which is administered subcutaneously every 3 weeks. Which of the following best explains the mechanism of action of the new medication that has been added to the controller medications?

You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X?

A 38-year-old man presents to his physician with recurrent episodes of facial swelling and abdominal pain. He reports that these episodes started when he was approximately 16 years of age. His mother also has similar episodes of swelling accompanied by swelling of her extremities. The vital signs include: blood pressure 140/80 mm Hg, heart rate 74/min, respiratory rate 17/min, and temperature 36.6℃ (97.8℉). His physical examination is unremarkable. The laboratory work-up shows the following findings: Test Result Normal range C1 esterase inhibitor 22% > 60% Complement C4 level 9 mg/dL 14–40 mg/dL Complement C2 level 0.8 mg/dL 1.1–3.0 mg/dL Complement component 1q 17 mg/dL 12–22 mg/dL Which of the following anti-hypertensive medications is contraindicated in this patient?

A 35-year-old woman comes to the physician because of blurred vision for the past 2 months. During this period, she has also had difficulty chewing and swallowing. She reports that her symptoms worsen throughout the day and improve with rest. There is no personal or family history of serious illness. The patient works as a teacher and has had a great deal of stress lately. She does not smoke and drinks a glass of wine occasionally. She takes no medications. Her temperature is 37°C (98.6°F), pulse is 68/min, and blood pressure is 130/80 mm Hg. Physical examination shows bilateral ptosis and mask-like facies. Muscle strength is decreased in both lower extremities. The anti–acetylcholine receptor (AChR) antibody test is positive. Electromyography shows a decremental response following repetitive nerve stimulation. Which of the following is the most appropriate next step in the management of this patient?

A 28-year-old female presents to her primary care doctor complaining of new onset blurry vision. She first noticed her vision getting blurry toward the end of the day several days ago. Since then, she reports that her vision has been fine when she wakes up but gets worse throughout the day. She has also noticed that her eyelids have started to droop before she goes to bed. On exam, she has bilateral ptosis that is worse on the right. Administering edrophonium to this patient leads to an immediate improvement in her symptoms. Which of the following is most likely true about this patient’s condition?