Infectious Diseases Practice Questions

Q: Which of the following is a chronic complication of malaria?

Both nephrotic syndrome and splenomegaly. The correct answer is Both nephrotic syndrome and splenomegaly because chronic or repeated exposure to malaria parasites leads to persistent immune activation and structural organ changes. 1. Nephrotic Syndrome: This is a classic chronic complication specifically associated with Plasmodium malariae. It results from the deposition of immune complexes in the glomerular basement membrane (Quartan Malarial Nephropathy). Unlike the acute kidney injury seen in P. falciparum, this is a chronic, progressive condition that often responds poorly to antimalarial therapy. 2. Splenomegaly: Chronic or recurrent malaria leads to persistent congestion and hyperplasia of the reticuloendothelial system [1]. A specific chronic manifestation is Hyperreactive Malarial Splenomegaly (HMS), formerly known as Tropical Splenomegaly Syndrome. It is characterized by massive splenomegaly, high titers of anti-malarial antibodies, and hypergammaglobulinemia (IgM). Why other options are incorrect: * Pneumonia: While pulmonary edema and ARDS are severe acute complications of P. falciparum malaria, pneumonia is typically a secondary bacterial superinfection rather than a direct chronic complication of the malaria parasite itself. High-Yield Clinical Pearls for NEET-PG: * HMS Treatment: Long-term antimalarial chemoprophylaxis (e.g., Proguanil or Chloroquine) is the treatment of choice for Hyperreactive Malarial Splenomegaly. * Blackwater Fever: An acute complication involving massive intravascular hemolysis and hemoglobinuria, usually associated with P. falciparum and quinine use. * Recrudescence vs. Relapse: P. falciparum causes recrudescence (sub-optimal treatment) [1], while P. vivax and P. ovale cause relapse due to hypnozoites in the liver [1].

Q: A 71-year-old man presents with low-grade fever, generalized malaise, and a feeling of being run-down. He has experienced weight loss and exhibits stigmata of chronic illness. There is no history of occupational exposure. On physical examination, vital signs are: pulse 110 bpm; temperature 99°F; respirations 19/min; blood pressure 90/60 mm Hg. The patient is frail and appears cachectic with temporal wasting. Other aspects of his physical exam are unremarkable. Laboratory data: Hb 10 g/dL; Hct 30%; MCV 90 fL; WBCs 3000/uL; differential normal; BUN 19 mg/dL; creatinine 1.0 mg/dL; sodium 129 mEq/L; potassium 5.0 mEq/L; ABGs (RA): pH 7.42, PCO2 35 mm Hg, PO2 58 mm Hg. Spirometry: FVC 60% of predicted; FEV1 60% of predicted. PPD skin test is negative (0 mm); induced sputum for AFB smear is negative. Chest radiograph is shown. What is the most likely diagnosis?

Miliary TB. ***Miliary TB*** - **Constitutional symptoms** (low-grade fever, malaise, weight loss, cachexia) in an elderly patient with **negative PPD** due to **anergy** (common in disseminated TB) strongly suggests miliary tuberculosis. - **Hyponatremia** (129 mEq/L) suggests **SIADH**, **hypoxemia** (PO2 58 mm Hg), and the classic **miliary pattern** on chest X-ray with diffuse **1-3 mm nodules** are characteristic findings. *Silicosis* - Requires significant **occupational exposure** to silica dust (mining, sandblasting), which is explicitly absent in this case. - Typically presents with **upper lobe fibrosis** and **eggshell calcification** of hilar lymph nodes, not miliary nodules. *Metastatic thyroid carcinoma* - Would typically show **larger, irregular nodules** rather than the uniform **miliary pattern** seen in this case. - Usually associated with a **known primary thyroid malignancy** and **thyroid function abnormalities**. *Sarcoidosis* - More common in **younger patients** (20-40 years) and often presents with **bilateral hilar lymphadenopathy**. - Typically shows **larger nodules** and **upper lobe predominance**, unlike the diffuse miliary pattern described here.

Q: Which of the following statements about cysticercosis is true?

Human cysticercosis is transmitted by the ingestion of ova. Cysticercosis is a systemic parasitic infection caused by the larval stage (*Cysticercus cellulosae*) of the pork tapeworm, **Taenia solium** [1]. **1. Why Option C is correct:** Human cysticercosis occurs when a human acts as an **accidental intermediate host**. This happens via the **ingestion of T. solium eggs (ova)** through contaminated food or water (fecal-oral route) or via autoinfection [1], [2]. Once ingested, the eggs hatch in the intestine, releasing oncospheres that migrate to tissues (brain, muscles, eyes) to form cysticerci. **2. Why other options are incorrect:** * **Option A:** *Echinococcus granulosus* causes Hydatid disease, not cysticercosis [1]. * **Option B:** In the life cycle of *T. solium*, **man is the definitive host** only for the adult tapeworm (intestinal taeniasis, acquired by eating undercooked pork containing cysticerci) [1], [2]. However, for **cysticercosis**, man acts as the intermediate host. * **Option D:** The treatment of choice for neurocysticercosis (NCC) involves **Albendazole** (preferred) or Praziquantel, often administered with corticosteroids to reduce inflammation. Levamisole is an anthelmintic used primarily for Ascariasis. **High-Yield Clinical Pearls for NEET-PG:** * **Neurocysticercosis (NCC):** The most common cause of adult-onset seizures in developing countries. * **Imaging:** CT/MRI shows the "starry sky" appearance (multiple calcified cysts) or a "hole-with-dot" appearance (scolex within the cyst). * **Key Distinction:** Ingesting **larvae** (in pork) leads to **Taeniasis** (intestinal); ingesting **eggs** (fecal-oral) leads to **Cysticercosis** (tissue) [1], [2].

Q: A young butcher cuts his forearm with a knife. Over the next week, he notices swelling, redness, and warmth at the site. Four days later, he presents to the emergency department with fever, shaking chills, and severe lower back pain. Physical examination reveals a temperature of 39.4 C (102.9 F), swelling in his forearm with an area of central softness, and tenderness to pressure over his lower spine. Laboratory data show a leukocyte count of 14,000/mm3 with 81% polymorphonuclear leukocytes. Blood cultures grew a gram-positive cocci in clusters on blood agar; colonies show a yellow pigment, and the organism is positive on mannitol/salt agar. The organism is catalase and coagulase positive. Which of the following is the most likely pathogen?

Staphylococcus aureus. ### Explanation **1. Why Staphylococcus aureus is Correct:** The clinical presentation describes a classic case of **Staphylococcus aureus** skin and soft tissue infection (SSTI) leading to hematogenous spread [1]. The patient’s occupation (butcher) increases the risk of skin trauma. The subsequent development of fever, chills, and spinal tenderness suggests **vertebral osteomyelitis** via hematogenous seeding [1]. The laboratory findings are definitive for *S. aureus*: * **Morphology:** Gram-positive cocci in clusters. * **Biochemical tests:** Catalase positive (differentiates from Streptococcus) and **Coagulase positive** (differentiates from Coagulase-negative Staphylococci like *S. epidermidis*) [1]. * **Culture:** Yellow pigment (hence the name *aureus*) and growth on **Mannitol Salt Agar (MSA)**, where it ferments mannitol to produce yellow colonies. **2. Why the Other Options are Incorrect:** * **Bacteroides fragilis (A):** An anaerobic Gram-negative rod, typically associated with intra-abdominal infections, not primary skin trauma in a butcher. * **Clostridium perfringens (B):** An anaerobic Gram-positive rod that causes gas gangrene (crepitus on exam). It does not present as cocci in clusters or grow on MSA. * **Escherichia coli (C):** A Gram-negative rod. While it can cause osteomyelitis (especially post-UTI), it would not be catalase/coagulase positive or show the described Gram stain morphology. **3. Clinical Pearls for NEET-PG:** * **S. aureus** is the most common cause of **acute osteomyelitis** and **pyogenic spinal infections** in adults. * **Mannitol Salt Agar** is both selective (high salt inhibits most bacteria) and differential (only *S. aureus* ferments mannitol) for this pathogen. * In intravenous drug users (IVDU), *S. aureus* is the most common cause of **tricuspid valve endocarditis**, which can also lead to hematogenous seeding of the spine [1].

Q: Which of the following is NOT seen in acute HIV syndrome?

Pneumonia. Explanation: Acute HIV Syndrome (Acute Retroviral Syndrome) occurs 2 to 4 weeks after initial infection, representing a burst of viral replication and a robust host immune response. It typically presents as a mononucleosis-like illness [1]. Why Option A (Pneumonia) is the correct answer: Pneumonia is **not** a feature of Acute HIV Syndrome. Pneumonia in HIV patients (such as *Pneumocystis jirovecii* or bacterial pneumonia) is an **opportunistic infection** that typically occurs during the advanced stage (AIDS), when the CD4+ T-cell count has significantly declined (usually 70% of cases), typically involving the axillary, cervical, and occipital nodes [1]. * **C & D. Myelopathy and Encephalitis:** Neurological manifestations occur in about 10–15% of patients during the acute phase. These include aseptic meningitis, encephalitis, peripheral neuropathy, and transverse myelopathy, caused by the direct neurotropic nature of the virus during primary seeding [1]. High-Yield Clinical Pearls for NEET-PG: * **Most common symptom:** Fever (96%), followed by lymphadenopathy and pharyngitis [1]. * **Dermatological finding:** A maculopapular rash involving the trunk and face is characteristic [1]. * **Laboratory findings:** High viral load (HIV-RNA), negative or indeterminate ELISA/Western Blot (the "window period"), and a high CD8+ T-cell count. * **Diagnosis:** Best confirmed by **HIV-RNA levels (NAT)** or **p24 antigen assay**.

Question 1

Which of the following is a chronic complication of malaria?

Accepted Answer

Both nephrotic syndrome and splenomegaly

Answer

Pneumonia

Answer

Nephrotic syndrome

Answer

Splenomegaly

Question 2

Serology of a young man shows HBsAg, but HBeAg is negative with normal levels of AST and ALT. He is asymptomatic. What is the next line of management?

Accepted Answer

Wait and watch

Answer

Antiviral therapy

Answer

Immunoglobulins

Answer

Liver transplant

Question 3

A 71-year-old man presents with low-grade fever, generalized malaise, and a feeling of being run-down. He has experienced weight loss and exhibits stigmata of chronic illness. There is no history of occupational exposure. On physical examination, vital signs are: pulse 110 bpm; temperature 99°F; respirations 19/min; blood pressure 90/60 mm Hg. The patient is frail and appears cachectic with temporal wasting. Other aspects of his physical exam are unremarkable. Laboratory data: Hb 10 g/dL; Hct 30%; MCV 90 fL; WBCs 3000/uL; differential normal; BUN 19 mg/dL; creatinine 1.0 mg/dL; sodium 129 mEq/L; potassium 5.0 mEq/L; ABGs (RA): pH 7.42, PCO2 35 mm Hg, PO2 58 mm Hg. Spirometry: FVC 60% of predicted; FEV1 60% of predicted. PPD skin test is negative (0 mm); induced sputum for AFB smear is negative. Chest radiograph is shown. What is the most likely diagnosis?

Accepted Answer

Miliary TB

Answer

Silicosis

Answer

Metastatic thyroid carcinoma

Answer

Sarcoidosis

Question 4

Which of the following is NOT a feature of dengue hemorrhagic fever?

Accepted Answer

Narrow pulse pressure

Answer

Thrombocytopenia

Answer

Elevated hematocrit

Answer

Positive tourniquet test

Question 5

Which of the following statements about cysticercosis is true?

Accepted Answer

Human cysticercosis is transmitted by the ingestion of ova

Answer

The causative agent is Echinococcus granulosus

Answer

The definitive host is man

Answer

Levamisole is the treatment of choice

Question 6

What is the increased risk factor for developing tuberculosis (TB) in a patient with a positive Mantoux test?

Accepted Answer

Adrenal steroid therapy

Answer

Human Immunodeficiency Virus (HIV) infection

Answer

Diabetes Mellitus (DM)

Answer

All the above

Question 7

A patient with an 8 cm x 8 cm abscess in the right lobe of the liver was treated with multiple aspirations and systemic amebicide. A cavity remains in the right lobe, which is now empty. A seven-day course of luminal amebicides has been completed. What is the recommended follow-up plan?

Accepted Answer

Ultrasound (USG) weekly for 1 month, followed by monthly USG until 1 year

Answer

Stool examination only

Answer

Ultrasound (USG) weekly for 3 months, followed by CT scan at 3 months

Answer

Ultrasound (USG) or CT scan monthly, and stool examination weekly

Question 8

A young butcher cuts his forearm with a knife. Over the next week, he notices swelling, redness, and warmth at the site. Four days later, he presents to the emergency department with fever, shaking chills, and severe lower back pain. Physical examination reveals a temperature of 39.4 C (102.9 F), swelling in his forearm with an area of central softness, and tenderness to pressure over his lower spine. Laboratory data show a leukocyte count of 14,000/mm3 with 81% polymorphonuclear leukocytes. Blood cultures grew a gram-positive cocci in clusters on blood agar; colonies show a yellow pigment, and the organism is positive on mannitol/salt agar. The organism is catalase and coagulase positive. Which of the following is the most likely pathogen?

Accepted Answer

Staphylococcus aureus

Answer

Bacteroides fragilis

Answer

Clostridium perfringens

Answer

Escherichia coli

Question 9

Which of the following is NOT seen in acute HIV syndrome?

Accepted Answer

Pneumonia

Answer

Lymphadenopathy

Answer

Myelopathy

Answer

Encephalitis

Question 10

Which of the following is NOT essential when managing a febrile neutropenic patient?

Accepted Answer

White cell infusion

Answer

Repeated hand washing by hospital personnel

Answer

Prophylactic antibiotics

Answer

Colony-stimulating factor for macrophages

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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