Infectious Diseases Practice Questions

Q: Fulminant Hepatitis E is typically seen in which demographic group?

Pregnant women. **Explanation:** Hepatitis E Virus (HEV) is a single-stranded RNA virus primarily transmitted via the fecal-oral route. While it usually causes a self-limiting illness in the general population, it is notorious for causing **Fulminant Hepatic Failure (FHF)** in **pregnant women**, particularly during the second and third trimesters. **1. Why Pregnant Women?** The mortality rate for HEV in the general population is low (0.5–4%), but in pregnant women, it skyrockets to **15–25%**. The exact pathogenesis is multifactorial, involving a shift in the Th1/Th2 cytokine balance, high levels of progesterone and estrogen (which may promote viral replication), and a diminished cell-mediated immune response. This leads to rapid hepatic necrosis and liver failure. **2. Analysis of Incorrect Options:** * **Infants:** While infants can contract HEV, they do not show a specific predisposition to fulminant failure compared to the high-risk profile of pregnancy. * **Adolescents:** In this age group, HEV is typically subclinical or presents as a mild, self-limiting icteric hepatitis. * **Malnourished males:** While malnutrition can worsen the prognosis of any infectious disease, there is no specific epidemiological link between malnourishment in males and the fulminant presentation of HEV. **3. NEET-PG High-Yield Pearls:** * **Virus Family:** Hepeviridae (Non-enveloped RNA virus). * **Genotypes:** Genotypes 1 and 2 are associated with waterborne epidemics in humans; Genotypes 3 and 4 are zoonotic (pork/deer meat). * **Chronic HEV:** Can occur in **immunocompromised** patients (e.g., organ transplant recipients), usually associated with Genotype 3. * **Extra-hepatic manifestations:** Guillain-Barré syndrome and Neuralgic amyotrophy. * **Prophylaxis:** The Hecolin vaccine is available in some countries (China) but not yet globally widespread.

Q: A young male presents with cough. The provided chest X-ray shows no known cardiac abnormality. Which of the following is most likely to be true about the patient?

The patient is likely to be immunocompromised.. ***The patient is likely to be immunocompromised.*** - The chest X-ray likely shows **bilateral perihilar interstitial infiltrates** with a **normal cardiac silhouette**, which is classic for **PCP (Pneumocystis jirovecii pneumonia)**. - PCP is an **opportunistic infection** that predominantly affects **immunocompromised patients**, particularly those with **HIV/AIDS** or other causes of severe immunosuppression. *Raised ACE levels are likely.* - Elevated **ACE levels** are typically associated with **sarcoidosis**, which would show bilateral hilar lymphadenopathy rather than interstitial infiltrates. - The **normal cardiac silhouette** and clinical presentation do not support sarcoidosis as the primary diagnosis. *Cold agglutinins will be positive.* - **Cold agglutinins** are characteristic of **Mycoplasma pneumoniae** infection, which typically causes unilateral lower lobe pneumonia. - The bilateral perihilar pattern seen here is not consistent with **typical Mycoplasma pneumonia** presentation. *Occupational history will provide an important clue to the diagnosis.* - **Occupational lung diseases** like **pneumoconiosis** typically develop over years of exposure and show different radiological patterns. - The acute presentation with cough and bilateral perihilar infiltrates is more consistent with an **infectious process** rather than occupational lung disease.

Q: What is the first sign of tetanus?

Trismus. Explanation: Tetanus is caused by the neurotoxin tetanospasmin, produced by Clostridium tetani. The toxin acts by blocking the release of inhibitory neurotransmitters (GABA and glycine) from Renshaw cells in the spinal cord, leading to unchecked muscle spasms [1]. Why Trismus is the correct answer: In generalized tetanus, the most common and classic presenting symptom is Trismus (lockjaw). This is due to the masseter muscle being highly sensitive to the toxin, leading to its involuntary contraction. This prevents the patient from opening their mouth fully and is considered the hallmark initial sign [1]. Analysis of Incorrect Options: * A. Dysphagia: While common, difficulty swallowing usually occurs shortly after the onset of trismus as the toxin affects the pharyngeal muscles. * B. Neck stiffness: This is a frequent early sign but typically follows trismus. It contributes to the later development of "Risus Sardonicus" (a characteristic grimace). * C. Back pain: This occurs as the disease progresses to involve the long muscles of the trunk, eventually leading to Opisthotonus (a backward arching of the head, neck, and spine). High-Yield Clinical Pearls for NEET-PG: * Risus Sardonicus: The characteristic facial expression caused by spasms of the facial muscles. * Opisthotonus: The bridge-like arching of the body due to extensor spasm. * Autonomic Instability: The most common cause of death in modern intensive care settings (labile BP, tachycardia, sweating). * Diagnosis: Purely clinical; wound cultures are positive in only ~30% of cases. * Management: Neutralize unbound toxin with Human Tetanus Immune Globulin (HTIG) and use Metronidazole as the preferred antibiotic.

Q: What is a common cause of P.F?

Thrombocytopenia. **Explanation:** In the context of Malaria (specifically *Plasmodium falciparum*), **Thrombocytopenia** is the most common hematological abnormality, occurring in up to 60-80% of cases. **Why Thrombocytopenia is the correct answer:** The reduction in platelet count in *P. falciparum* (P.f) malaria is multifactorial. Key mechanisms include: 1. **Splenic Sequestration:** Increased pooling of platelets in the spleen. 2. **Immune-mediated Destruction:** Production of anti-platelet IgG antibodies that lead to platelet lysis. 3. **Platelet Activation:** Direct interaction between the parasite and platelets, leading to premature removal from circulation. While it is a hallmark of the infection, it is rarely associated with spontaneous bleeding unless counts drop severely. **Analysis of Incorrect Options:** * **B. DIC:** While DIC is a severe complication of cerebral malaria or "Algid malaria," it is far less common than simple thrombocytopenia. * **C. Hemolysis:** Although malaria causes obligatory hemolysis of infected RBCs, it is a clinical feature/process rather than the most characteristic laboratory finding used to distinguish the severity of P.f in common MCQ contexts compared to the frequency of low platelets. * **D. Hematemesis:** This is a rare presentation usually associated with severe coagulopathy or portal hypertension, not a common feature of P.f. **NEET-PG High-Yield Pearls:** * **Most common cause of death in P.f:** Cerebral Malaria. * **Blackwater Fever:** Severe intravascular hemolysis leading to hemoglobinuria, caused by P.f (often associated with irregular Quinine use). * **Maurer’s Dots:** Coarse granulations seen in RBCs infected with *P. falciparum*. * **Double Infection:** P.f is the only species where multiple parasites are commonly seen within a single RBC (Accole or Applique forms).

Q: A young man presents with a history of 6 kg weight loss in 3 months and on examination is found to have generalized lymph node enlargement. Which of the following is the LEAST likely diagnosis?

Chronic malaria. **Explanation:** The clinical presentation of significant weight loss (6 kg in 3 months) and **generalized lymphadenopathy** (enlargement of two or more non-contiguous lymph node stations) suggests a systemic chronic infection or malignancy [1]. **Why Chronic Malaria is the correct (least likely) answer:** Malaria typically presents with fever, anemia, and **splenomegaly**. While "Tropical Splenomegaly Syndrome" (Hyperreactive Malarial Splenomegaly) can occur in chronic cases, it does **not** typically cause generalized lymphadenopathy or profound weight loss. Lymph node enlargement is not a characteristic feature of the *Plasmodium* life cycle in humans. **Analysis of Incorrect Options:** * **HIV-AIDS:** Persistent Generalized Lymphadenopathy (PGL) is a hallmark of early symptomatic HIV [3]. Significant weight loss (Wasting Syndrome) is a defining feature of progression to AIDS [3]. * **Lymphoma:** Both Hodgkin and Non-Hodgkin Lymphomas are classic causes of generalized lymphadenopathy [2]. "B-symptoms," including significant unexplained weight loss (>10% in 6 months), are key diagnostic criteria [2]. * **Disseminated Tuberculosis:** In endemic regions like India, TB is a leading cause of generalized lymphadenopathy (miliary or disseminated TB) [1]. It is almost always accompanied by constitutional symptoms like weight loss and night sweats [1]. **NEET-PG Clinical Pearls:** * **Definition:** Generalized lymphadenopathy involves $\ge$ 2 non-contiguous node stations. * **Mnemonic for Generalized Lymphadenopathy (MIAMI):** **M**alignancy, **I**nfectious (HIV, EBV, TB), **A**utoimmune (SLE, RA), **M**iscellaneous (Sarcoidosis), **I**atrogenic (Phenytoin) [2]. * **Weight Loss:** In NEET-PG questions, "Weight loss + Lymphadenopathy" should first trigger thoughts of **TB, HIV, or Malignancy.**

Q: The tourniquet test is considered positive if the number of petechiae exceeds which threshold per square inch?

20 petechiae per square inch. **Explanation:** The **Tourniquet Test** (also known as the Hess test) is a clinical diagnostic tool used to assess capillary fragility and is a key component of the WHO case definition for **Dengue Hemorrhagic Fever (DHF)**. **Why Option D is correct:** The test is performed by inflating a blood pressure cuff to a point midway between the systolic and diastolic blood pressure for 5 minutes. After deflating the cuff and waiting 2 minutes for skin color to return to normal, the petechiae are counted within a 1-square-inch (2.5 cm x 2.5 cm) area. A result is considered **positive** if there are **20 or more petechiae per square inch**. This indicates increased capillary permeability and fragility, often seen in the setting of thrombocytopenia or vascular dysfunction associated with Dengue. **Why other options are incorrect:** * **Options A, B, and C (50, 40, 30 petechiae):** These thresholds are significantly higher than the standardized WHO criteria. Using these values would result in a high false-negative rate, failing to identify patients at risk for plasma leakage and hemorrhagic complications. **NEET-PG High-Yield Pearls:** * **Dengue Classification:** The tourniquet test is a marker of "Dengue with warning signs" according to the 2009 WHO classification. * **Sensitivity:** While specific, the test may be negative during the early febrile phase or in patients with profound shock. * **Differential Diagnosis:** Besides Dengue, a positive test can be seen in ITP, Vitamin C deficiency (Scurvy), and Scarlet Fever. * **Calculation Tip:** The pressure used is the **Mean Arterial Pressure (MAP)** or simply the midpoint: $(SBP + DBP) / 2$.

Question 1

Fulminant Hepatitis E is typically seen in which demographic group?

Accepted Answer

Pregnant women

Answer

Infants

Answer

Adolescents

Answer

Malnourished males

Question 2

A young male presents with cough. The provided chest X-ray shows no known cardiac abnormality. Which of the following is most likely to be true about the patient?

Accepted Answer

The patient is likely to be immunocompromised.

Answer

Raised ACE levels are likely.

Answer

Cold agglutinins will be positive.

Answer

Occupational history will provide an important clue to the diagnosis.

Question 3

What is the first sign of tetanus?

Accepted Answer

Trismus

Answer

Dysphagia

Answer

Neck stiffness

Answer

Back pain

Question 4

A 30-year-old male with a past history of otitis media and mastoiditis presented with severe throbbing headache, high-grade fever, nausea, vomiting, confusion, and gait disturbance. On examination, he was febrile, ataxic with nystagmus, and there was no neck rigidity. MRI brain with contrast revealed a brain abscess. Which of the following is the likely site of the brain abscess?

Accepted Answer

Cerebellum

Answer

Temporal lobe

Answer

Frontal lobe

Answer

Midbrain

Question 5

A patient with HIV is positive, with a viral load of 750,000 copies of HIV RNA/ml and a total CD4 count of 50. This patient is at an increased risk for several infectious diseases. For which of the following diseases does this patient have no added risk compared to an immunocompetent host?

Accepted Answer

Pneumocystis pneumonia

Answer

Mycobacterial disease

Answer

Kaposi's sarcoma

Answer

Pneumococcal pneumonia

Question 6

What is a common cause of P.F?

Accepted Answer

Thrombocytopenia

Answer

Disseminated Intravascular Coagulation (DIC)

Answer

Hemolysis

Answer

Hematemesis

Question 7

A young man presents with a history of 6 kg weight loss in 3 months and on examination is found to have generalized lymph node enlargement. Which of the following is the LEAST likely diagnosis?

Accepted Answer

Chronic malaria

Answer

HIV-AIDS

Answer

Lymphoma

Answer

Disseminated tuberculosis

Question 8

A 68-year-old woman develops new symptoms of burning when voiding. She has no fever, chills, or back discomfort. Her urinalysis reveals numerous white cells and bacteria. Which of the following medical comorbidities is most likely to coexist in this patient?

Accepted Answer

diabetes mellitus

Answer

anemia

Answer

exercise

Answer

influenza

Question 9

The tourniquet test is considered positive if the number of petechiae exceeds which threshold per square inch?

Accepted Answer

20 petechiae per square inch

Answer

50 petechiae per square inch

Answer

40 petechiae per square inch

Answer

30 petechiae per square inch

Question 10

Which of the following statements about Pneumocystis pneumonia is true?

Accepted Answer

The drug of choice is Trimethoprim-Sulfamethoxazole (Cotrimoxazole).

Answer

The causative organism is a protozoan.

Answer

The most common radiological appearance is a bat wing distribution of infiltrates with pneumocysts in peripheral fields.

Answer

Steroids have no role in the therapy of Pneumocystis pneumonia.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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