Parasites/Fungi US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Parasites/Fungi. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Parasites/Fungi US Medical PG Question 1: A 22-year-old man presents with abdominal cramps and diarrhea over the last few weeks. He notes that several of his bowel movements have a small amount of blood. Past medical history is significant for an intermittent cough that has been persistent since returning from Mexico last month. The patient takes no current medications. On physical examination, there is diffuse tenderness to palpation. Which of the following medications is indicated for this patient’s condition?
- A. Pyrantel
- B. Praziquantel
- C. Albendazole
- D. Mebendazole
- E. Ivermectin (Correct Answer)
Parasites/Fungi Explanation: ***Ivermectin***
- This patient's symptoms (abdominal cramps, bloody diarrhea, persistent cough, recent travel to Mexico) are highly suggestive of **Strongyloidiasis**. **Ivermectin** is the drug of choice for this parasitic infection.
- Strongyloidiasis larvae can cause a **transient cough** as they migrate through the lungs, and adult worms in the intestines lead to gastrointestinal symptoms like **diarrhea** and abdominal pain.
*Pyrantel*
- **Pyrantel** is primarily effective against **pinworms**, **roundworms**, and **hookworms**, but not Strongyloides.
- It works by neuromuscular blockade, causing paralysis and expulsion of the worms.
*Praziquantel*
- **Praziquantel** is the drug of choice for treating **tapeworm** infections (e.g., Taenia species) and **schistosomiasis**.
- It acts by increasing the permeability of the worm's cells to calcium, leading to paralysis and death.
*Albendazole*
- **Albendazole** is a broad-spectrum anthelmintic effective against many intestinal nematodes, including **hookworm**, **roundworm**, and **whipworm**, and some tissue nematodes.
- While it has some activity against Strongyloides, **Ivermectin is generally preferred** due to higher efficacy and fewer side effects in many cases of strongyloidiasis.
*Mebendazole*
- **Mebendazole** is effective against various intestinal worms such as **pinworms**, **roundworms**, and **hookworms**.
- Its mechanism of action involves inhibiting microtubule synthesis, thereby impairing glucose uptake by the worms.
Parasites/Fungi US Medical PG Question 2: A scientist in Boston is studying a new blood test to detect Ab to the parainfluenza virus with increased sensitivity and specificity. So far, her best attempt at creating such an exam reached 82% sensitivity and 88% specificity. She is hoping to increase these numbers by at least 2 percent for each value. After several years of work, she believes that she has actually managed to reach a sensitivity and specificity even greater than what she had originally hoped for. She travels to South America to begin testing her newest blood test. She finds 2,000 patients who are willing to participate in her study. Of the 2,000 patients, 1,200 of them are known to be infected with the parainfluenza virus. The scientist tests these 1,200 patients’ blood and finds that only 120 of them tested negative with her new test. Of the following options, which describes the sensitivity of the test?
- A. 82%
- B. 86%
- C. 98%
- D. 90% (Correct Answer)
- E. 84%
Parasites/Fungi Explanation: ***90%***
- **Sensitivity** is calculated as the number of **true positives** divided by the total number of individuals with the disease (true positives + false negatives).
- In this scenario, there were 1200 infected patients (total diseased), and 120 of them tested negative (false negatives). Therefore, 1200 - 120 = 1080 patients tested positive (true positives). The sensitivity is 1080 / 1200 = 0.90, or **90%**.
*82%*
- This value was the **original sensitivity** of the test before the scientist improved it.
- The question states that the scientist believes she has achieved a sensitivity "even greater than what she had originally hoped for."
*86%*
- This value is not directly derivable from the given data for the new test's sensitivity.
- It might represent an intermediate calculation or an incorrect interpretation of the provided numbers.
*98%*
- This would imply only 24 false negatives out of 1200 true disease cases, which is not the case (120 false negatives).
- A sensitivity of 98% would be significantly higher than the calculated 90% and the initial stated values.
*84%*
- This value is not derived from the presented data regarding the new test's performance.
- It could be mistaken for an attempt to add 2% to the original 82% sensitivity, but the actual data from the new test should be used.
Parasites/Fungi US Medical PG Question 3: A family doctor in a rural area is treating a patient for dyspepsia. The patient had chronic heartburn and abdominal pain for the last 2 months and peptic ulcer disease due to a suspected H. pylori infection. For reasons relating to affordability and accessibility, the doctor decides to perform a diagnostic test in the office that is less invasive and more convenient. Which of the following is the most likely test used?
- A. Steiner's stain
- B. Culture of organisms from gastric specimen
- C. Stool antigen test (Correct Answer)
- D. Detection of the breakdown products of urea in biopsy
- E. Serology (ELISA testing)
Parasites/Fungi Explanation: ***Stool antigen test***
- This **non-invasive** and **cost-effective** test detects *H. pylori* antigens in stool, making it suitable for a rural setting with limited resources.
- It is highly sensitive and specific, useful for both initial diagnosis and confirming eradication after treatment.
*Steiner's stain*
- **Steiner's stain** (Steiner silver stain) is primarily used for histological visualization of *Legionella* species, and **not for** *H. pylori* detection in routine clinical practice.
- It requires an **endoscopic biopsy**, making it more invasive and costly than the stool antigen test.
*Culture of organisms from gastric specimen*
- This method requires an **endoscopic biopsy** and specialized culture facilities, which may not be available in a rural doctor's office.
- It is more expensive and time-consuming, and primarily used when **antibiotic resistance** is suspected.
*Detection of the breakdown products of urea in biopsy*
- This refers to the **rapid urease test** (e.g., CLOtest), which is performed on a **gastric biopsy** obtained during endoscopy.
- While quick, it is an **invasive procedure** requiring endoscopy, which contradicts the patient's and doctor's preferences for a less invasive test.
*Serology (ELISA testing)*
- **Serology** detects antibodies to *H. pylori* but cannot differentiate between **active infection** and **past exposure**.
- Its utility in monitoring eradication is limited, and it's generally not recommended as the primary diagnostic test due to its inability to confirm active infection.
Parasites/Fungi US Medical PG Question 4: A 45-year-old woman comes to the physician because of a 5-kg (11-lb) weight loss and difficulty swallowing. She is able to swallow liquids without difficulty but feels like solid foods get stuck in her throat. Physical examination shows taut skin and limited range of motion of the fingers. There are telangiectasias over the cheeks. An esophageal motility study shows absence of peristalsis in the lower two-thirds of the esophagus and decreased lower esophageal sphincter pressure. Further evaluation of this patient is most likely to show which of the following?
- A. Microcytic, pale red blood cells
- B. Budding yeasts on the oral mucosa
- C. Arteriolar wall thickening in the kidney (Correct Answer)
- D. Amyloid deposits in the liver
- E. Parasite nests in the myocardium
Parasites/Fungi Explanation: **Arteriolar wall thickening in the kidney**
* The patient's presentation is classic for **Systemic Sclerosis (Scleroderma)**: progressive dysphagia for solids, **taut skin** (cutaneous sclerosis), sclerodactyly (limited finger motion), **telangiectasias**, and esophageal dysmotility with absent peristalsis and decreased LES pressure.
* **Renal involvement** is a major systemic complication of scleroderma. **Scleroderma renal crisis** occurs in 10-15% of patients and involves proliferative vasculopathy with **arteriolar wall thickening** (particularly affecting afferent renal arterioles), leading to acute kidney injury and malignant hypertension.
* This histologic finding of **arterial intimal proliferation and medial thickening** is the hallmark of scleroderma renal crisis and would be seen on kidney biopsy.
*Microcytic, pale red blood cells*
* This finding suggests **iron deficiency anemia** from chronic GI bleeding or malabsorption.
* While patients with scleroderma can develop **esophageal dysmotility** leading to reflux and Barrett's esophagus, and intestinal involvement causing malabsorption, iron deficiency anemia is not the most direct or specific systemic complication expected with this presentation.
*Budding yeasts on the oral mucosa*
* This indicates **oral candidiasis (thrush)**, seen in immunosuppressed patients or those with esophageal dysmotility.
* While scleroderma patients with severe esophageal dysmotility can develop candida esophagitis, oral candidiasis is not a primary systemic manifestation of the disease itself and would be secondary to esophageal stasis.
*Amyloid deposits in the liver*
* **Amyloidosis** involves extracellular deposition of insoluble fibrillar proteins in various organs.
* The clinical presentation here (taut skin, telangiectasias, specific esophageal findings with decreased LES pressure) is characteristic of scleroderma, not amyloidosis. Amyloidosis typically presents with nephrotic syndrome, hepatomegaly, macroglossia, and cardiac involvement—different from this patient's features.
*Parasite nests in the myocardium*
* This describes **Chagas disease** (caused by *Trypanosoma cruzi*), which causes **megaesophagus** and cardiomyopathy.
* While Chagas can cause esophageal dysmotility, it presents with **dilated esophagus** (megaesophagus) rather than the scleroderma pattern, and lacks the characteristic **skin changes** (taut skin, telangiectasias) and **decreased LES pressure** seen in this patient.
Parasites/Fungi US Medical PG Question 5: A 46-year-old man comes to the physician because of a 1-week history of headache, muscle pain, and recurrent fever spikes that occur without a noticeable rhythm. Two weeks ago, he returned from a 5-week-long world trip during which he climbed several mountains in India, Africa, and Appalachia. Chemoprophylaxis with chloroquine was initiated one week prior to the trip. Physical examination shows jaundice. The spleen is palpated 2 cm below the left costal margin. His hemoglobin concentration is 10 g/dL. A photomicrograph of a peripheral blood smear is shown. Which of the following agents is the most likely cause of this patient's findings?
- A. Chikungunya virus
- B. Trypanosoma cruzi
- C. Leishmania donovani
- D. Plasmodium falciparum (Correct Answer)
- E. Trypanosoma brucei
Parasites/Fungi Explanation: **Plasmodium falciparum**
- The image shows **multiple ring forms** and **applique forms** within red blood cells, which are characteristic of *Plasmodium falciparum* malaria. The clinical presentation of **headache, muscle pain, recurrent fever spikes without a noticeable rhythm, jaundice, splenomegaly, and anemia (Hb 10 g/dL)** in a traveler returning from India and Africa is highly consistent with malaria, especially given the chloroquine chemoprophylaxis which is often ineffective against chloroquine-resistant strains of *P. falciparum*.
- *P. falciparum* can cause severe disease, including **anemia** due to red blood cell destruction and **jaundice** due to hemolysis and liver involvement, and is notorious for its **irregular fever patterns** early in the infection cycle.
*Chikungunya virus*
- Chikungunya typically presents with **high fever, severe polyarthralgia**, and rash, but does not cause the parasitemia or specific red blood cell morphology seen in the image.
- While present in endemic regions like India and Africa, it does not lead to **anemia, splenomegaly, or jaundice** to the extent seen in this patient, nor does it appear on a blood smear as intracellular parasites.
*Trypanosoma cruzi*
- *Trypanosoma cruzi* causes **Chagas disease**, which is endemic to **Central and South America**, not India or Africa.
- While it can be found in blood smears during the acute phase (trypomastigotes), its morphology differs significantly from the ring forms seen, and the overall clinical picture of **fever, jaundice, and marked splenomegaly with characteristic RBC parasites** does not fit Chagas disease.
*Leishmania donovani*
- *Leishmania donovani* causes **visceral leishmaniasis (kala-azar)**, characterized by **prolonged fever, splenomegaly, hepatomegaly, pancytopenia**, and weight loss.
- While present in India and Africa, the parasites (**amastigotes**) are typically found within **macrophages** in bone marrow, spleen, or liver aspirates, not as ring forms within red blood cells on a peripheral blood smear.
*Trypanosoma brucei*
- *Trypanosoma brucei* causes **African sleeping sickness**, which involves **fever, headache, joint pain, neurological symptoms**, and lymphadenopathy (Winterbottom's sign).
- The parasites (trypomastigotes) are observed extracellularly in the blood, lymph, or CSF, and have a distinct **elongated, flagellated morphology** that is completely different from the intracellular ring forms seen in the provided image.
More Parasites/Fungi US Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
