Infectious Diseases Practice Questions

Q: Ablett classification is used for grading which of the following conditions?

Tetanus. **Explanation:** The **Ablett Classification** is the standard clinical tool used to grade the severity of **Tetanus**. It categorizes the disease based on the presence and intensity of symptoms such as trismus (lockjaw), muscle spasms, and autonomic dysfunction. * **Grade I (Mild):** Mild trismus, general spasticity, no respiratory distress, and no spasms. * **Grade II (Moderate):** Moderate trismus, rigid muscles, and brief, mild spasms. * **Grade III (Severe):** Severe trismus, generalized rigidity, and frequent, prolonged spasms with respiratory distress. * **Grade IV (Very Severe):** All features of Grade III plus severe **autonomic instability** (hypertension, tachycardia, or arrhythmia). **Why other options are incorrect:** * **Hidradenitis suppurativa:** Graded using the **Hurley Staging System** (Stage I-III). * **Pyogenic abscess:** These are typically described by anatomical location or etiology rather than a specific eponymized grading system like Ablett. * **Pyogenic granuloma:** This is a benign vascular tumor of the skin or mucous membranes; it does not have a formal severity classification system used in clinical practice. **NEET-PG High-Yield Pearls:** * **Tetanus Toxin:** *Tetanospasmin* acts by blocking the release of inhibitory neurotransmitters (**GABA and Glycine**) from Renshaw cells in the spinal cord. * **First Sign:** Trismus (lockjaw) is the most common presenting symptom. * **Risus Sardonicus:** A characteristic "sneering" facial expression due to facial muscle spasms. * **Management:** The priority is maintaining the airway, administering Metronidazole (preferred over Penicillin), and giving Human Tetanus Immunoglobulin (HTIG).

Q: What is the most common chronic viral illness?

Hepatitis C. **Explanation:** The correct answer is **Hepatitis C (HCV)**. The question asks for the most common **chronic** viral illness, referring to the rate of chronicity following an acute infection. **1. Why Hepatitis C is correct:** Hepatitis C is notorious for its high propensity to persist in the body [1]. Approximately **75%–85%** of individuals infected with HCV fail to clear the virus and progress to chronic infection [1]. This high rate of chronicity occurs because the virus frequently undergoes genetic mutations (due to lack of proofreading by its RNA polymerase), allowing it to evade the host's immune response. **2. Why the other options are incorrect:** * **Hepatitis A:** This is an enterically transmitted virus (fecal-oral route) that causes only acute hepatitis. It **never** causes chronic infection. * **Hepatitis B (HBV):** While HBV is a major cause of chronic liver disease globally, the risk of chronicity depends on the age of acquisition. In adults, only **5%–10%** of cases become chronic [1]. Although the absolute number of people with chronic HBV is high, the *rate* of chronicity per infection is significantly lower than HCV [1]. * **Hepatitis D (HDV):** HDV is a defective virus that requires the presence of HBsAg to replicate. While it can cause severe chronic disease (especially in superinfections), it is far less common than HCV in the general population. **High-Yield NEET-PG Pearls:** * **Highest Chronicity Rate:** Hepatitis C (~80%). * **Most Common Cause of Post-Transfusion Hepatitis:** Hepatitis C (historically, before screening). * **Age and HBV Chronicity:** In neonates, HBV chronicity is **90%**, whereas in adults, it is **<10%** [1]. * **HCV Screening:** The first-line test is Anti-HCV antibodies; the confirmatory test is HCV-RNA (PCR) [1]. * **Treatment:** HCV is now considered "curable" with Direct-Acting Antivirals (DAAs) like Sofosbuvir.

Q: Which of the following is NOT a major feature of AIDS?

Cough lasting longer than 1 month. This question is based on the **WHO Case Definition for AIDS Surveillance**, which categorizes clinical signs into Major and Minor criteria. [1] ### **Explanation of the Correct Answer** **D. Cough lasting longer than 1 month** is the correct answer because it is classified as a **Minor Sign**, not a major feature. [1] While respiratory infections (like *Pneumocystis jirovecii* or Tuberculosis) are common in AIDS patients, a chronic cough is considered a non-specific symptom that requires further investigation but does not carry the same diagnostic weight as the major signs in the surveillance definition. [1] ### **Analysis of Incorrect Options (Major Signs)** The WHO clinical criteria for AIDS in adults require at least **two major signs** associated with at least **one minor sign**. The major signs include: * **A. Fever lasting >1 month:** Persistent or intermittent pyrexia is a hallmark of advanced HIV/AIDS. [1] * **B. Diarrhea lasting >1 month:** Chronic diarrhea (often due to Cryptosporidium or CMV) is a primary indicator of the wasting syndrome. [1] * **C. Weight loss >10% of body weight:** Also known as "Slim Disease," involuntary profound weight loss is a cardinal major feature. [1] ### **Clinical Pearls for NEET-PG** * **Minor Signs of AIDS:** Persistent cough (>1 month), generalized pruritic dermatitis, recurrent herpes zoster, oropharyngeal candidiasis, and generalized lymphadenopathy. [1] * **The "Slim Disease":** In Africa, AIDS was historically referred to as Slim Disease due to the triad of fever, diarrhea, and massive weight loss. [1] * **Exception:** The presence of **Generalized Kaposi Sarcoma** or **Cryptococcal Meningitis** is sufficient by itself for the diagnosis of AIDS under these criteria. * **CD4 Count:** Remember that regardless of clinical signs, a **CD4 count <200 cells/mm³** is the laboratory definition of AIDS.

Q: Acalculous cholecystitis can be seen in all the following conditions except?

Malaria. Acalculous cholecystitis (AC) refers to acute inflammation of the gallbladder in the absence of gallstones. It typically occurs in critically ill patients or as a complication of specific systemic infections [1]. **Why Malaria is the correct answer:** While Malaria (especially *P. falciparum*) can cause multi-organ dysfunction, including jaundice and hepatomegaly, **acalculous cholecystitis is not a recognized or typical complication of Malaria.** Jaundice in malaria is primarily pre-hepatic (hemolysis) or hepatocellular, rather than obstructive or related to gallbladder wall inflammation. **Analysis of incorrect options:** * **Enteric Fever (Typhoid):** The gallbladder is a primary site for *Salmonella typhi* colonization. It can cause acute acalculous cholecystitis during the illness or lead to a chronic carrier state. * **Dengue Hemorrhagic Fever (DHF):** Gallbladder wall thickening and acalculous cholecystitis are well-documented in DHF. It is often used as a marker of plasma leakage and disease severity. * **Leptospirosis:** This zoonosis can cause vasculitis and localized inflammation leading to acalculous cholecystitis, particularly in the pediatric population or severe cases (Weil’s disease). **High-Yield Clinical Pearls for NEET-PG:** 1. **Risk Factors for AC:** Major trauma, burns, prolonged fasting (TPN), post-cardiac surgery, and sepsis [1]. 2. **Pathogenesis:** Primarily involves gallbladder stasis and ischemia rather than stone obstruction. 3. **Imaging:** Ultrasound is the initial investigation of choice; look for gallbladder wall thickening (>4mm), pericholecystic fluid, and a positive **sonographic Murphy’s sign** in the absence of stones. 4. **Other Infectious Causes:** HIV (CMV/Cryptosporidium), Cholera, and Brucellosis.

Q: Which of the following is NOT involved in leprosy?

Central Nervous System (CNS). **Explanation:** The correct answer is **A. Central Nervous System (CNS)**. **Why CNS is not involved:** *Mycobacterium leprae* has a unique predilection for cooler areas of the body. The organism thrives at temperatures between **30°C and 33°C**. The Central Nervous System (brain and spinal cord) is protected by the blood-brain barrier and maintains a core body temperature of approximately **37°C**, which is inhibitory to the growth and survival of *M. leprae*. Therefore, leprosy characteristically spares the CNS. **Why the other options are involved:** * **Skin (C):** This is the most common site of involvement [1]. Lesions range from hypopigmented patches in Tuberculoid leprosy to diffuse infiltration and nodules (lepromas) in Lepromatous leprosy. * **Testis (B):** The testes are located outside the body cavity to maintain a lower temperature, making them a prime target. Involvement can lead to orchitis, testicular atrophy, and subsequent sterility or gynecomastia [1]. * **Cornea (D):** The anterior segment of the eye is cooler than the posterior segment. Leprosy frequently affects the cornea (keratitis), iris, and ciliary body, potentially leading to blindness [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Target Tissues:** *M. leprae* primarily affects the skin, peripheral nerves (especially the ulnar, common peroneal, and posterior tibial), anterior chamber of the eye, upper respiratory tract mucosa, and testes [1]. * **Nerve Involvement:** It is the most common cause of peripheral neuropathy worldwide. * **Immune Response:** The clinical spectrum depends on the host’s **Cell-Mediated Immunity (CMI)**; strong CMI leads to Tuberculoid (TT), while weak CMI leads to Lepromatous (LL) leprosy [1]. * **Cardinal Signs:** Hypopigmented patches with loss of sensation, thickened peripheral nerves, and a positive slit-skin smear [1].

Q: In the serological testing for HIV infection, an early positive ELISA is primarily due to the detection of which of the following?

P24 antigen. **Explanation:** The correct answer is **D. P24 antigen**. **1. Why P24 antigen is correct:** The p24 protein is a structural component of the HIV viral capsid [1]. During the early stages of infection (the "window period"), there is a massive burst of viral replication before the body has time to mount a measurable antibody response. The **p24 antigen** becomes detectable in the serum as early as **1 to 3 weeks** after exposure. Modern **4th generation ELISA kits** (the current gold standard for screening) are designed to detect both the p24 antigen and HIV-1/2 antibodies simultaneously. This significantly narrows the window period compared to older tests [1]. **2. Why the other options are incorrect:** * **A & B (p24 and gp120 antibodies):** Antibodies against HIV proteins (like p24, gp120, or gp41) typically take **3 to 12 weeks** to reach detectable levels (seroconversion) [1]. Therefore, they are not the "earliest" markers in a positive ELISA. * **C (gp120 antigen):** While gp120 is a major envelope glycoprotein, it is not the primary antigen targeted in standard diagnostic ELISA screening. The p24 antigen is produced in much higher quantities and is the established marker for early detection. **Clinical Pearls for NEET-PG:** * **Window Period:** The time between infection and the point when a test can detect the virus. 4th Gen ELISA reduces this to ~14 days. * **Order of appearance of markers:** HIV-RNA (by PCR) → p24 Antigen → HIV Antibodies. * **Confirmatory Test:** While ELISA is for screening, the **Western Blot** (detecting antibodies to p24, gp41, and gp120/160) was historically the confirmatory test [1], though it is now being replaced by HIV-1/HIV-2 antibody differentiation immunoassays. * **Best initial test for a neonate born to an HIV+ mother:** HIV-DNA PCR (because maternal IgG antibodies cross the placenta, making ELISA unreliable).

Question 1

Ablett classification is used for grading which of the following conditions?

Accepted Answer

Tetanus

Answer

Hidradenitis suppurativa

Answer

Pyogenic abscess

Answer

Pyogenic granuloma

Question 2

What is the most common chronic viral illness?

Accepted Answer

Hepatitis C

Answer

Hepatitis A

Answer

Hepatitis B

Answer

Hepatitis D

Question 3

Which of the following is NOT a major feature of AIDS?

Accepted Answer

Cough lasting longer than 1 month

Answer

Fever lasting longer than 1 month

Answer

Diarrhea lasting longer than 1 month

Answer

Loss of more than 10% of body weight

Question 4

A 35-year-old HIV-positive man presents with a 6-month history of progressive memory loss and incontinence. He is currently on zidovudine and a protease inhibitor. Examination reveals deficits in cognitive and fine motor control functions. His CD4 cell count is 25/mm
3. MRI studies show moderate brain atrophy with no focal lesions. Lumbar puncture shows no cerebrospinal fluid abnormalities. What is the most likely diagnosis?

Accepted Answer

HIV encephalitis

Answer

CMV encephalitis

Answer

Cryptococcal meningoencephalitis

Answer

HIV myelopathy

Question 5

Which variant of immunoblastic lymphoma is primarily seen in HIV patients?

Accepted Answer

Primary Effusion Lymphoma

Answer

Centroblastic Lymphoma

Answer

Anaplastic Lymphoma

Answer

Any of the Above

Question 6

Acalculous cholecystitis can be seen in all the following conditions except?

Accepted Answer

Malaria

Answer

Enteric fever

Answer

Dengue hemorrhagic fever

Answer

Leptospirosis

Question 7

Which of the following is NOT involved in leprosy?

Accepted Answer

Central Nervous System (CNS)

Answer

Testis

Answer

Skin

Answer

Cornea

Question 8

In which of the following conditions is the pneumococcal vaccine indicated?

Accepted Answer

HIV infection

Answer

Patients who have undergone splenectomy

Answer

Sickle cell anemia

Answer

Corticosteroid therapy

Question 9

A 35-year-old man presents with an 18 kg weight loss over the preceding 4 months. He reports no dieting, but experiences abdominal pain, nausea, and diarrhea. He also has a chronic cough. Sputum studies reveal Pneumocystis carinii, and esophagogastroduodenoscopy with biopsy shows Candida and Herpes in the esophagus. Which group of viruses is the causative agent of this patient's underlying disease?

Accepted Answer

Retroviridae

Answer

Caliciviridae

Answer

Coronaviridae

Answer

Flaviviridae

Question 10

In the serological testing for HIV infection, an early positive ELISA is primarily due to the detection of which of the following?

Accepted Answer

P24 antigen

Answer

P24 antibody

Answer

Gp 120 antibody

Answer

Gp 120 antigen

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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