Infectious Diseases Practice Questions

Q: Which of the following conditions are associated with Hepatitis C Virus (HCV)?

Scleroderma. **Explanation:** Hepatitis C Virus (HCV) is unique among viral hepatitides for its strong association with various **extrahepatic manifestations**. **1. Why Scleroderma is the Correct Answer:** While HCV is classically associated with several autoimmune and rheumatological conditions, **Scleroderma (Systemic Sclerosis) is NOT typically associated with HCV.** In the context of this specific question (likely a "Which of the following is NOT associated" or "Except" style question common in NEET-PG), Scleroderma stands out as the outlier. Most literature focuses on HCV's link to Sjögren’s syndrome or Lichen Planus rather than Scleroderma. **2. Analysis of Other Options:** * **Cryoglobulinemia (Option C):** This is the **most common** extrahepatic manifestation of HCV. Specifically, **Mixed Cryoglobulinemia (Type II and III)** occurs in up to 50% of HCV patients, leading to vasculitis, glomerulonephritis, and palpable purpura. * **Anti-LKM-1 antibody (Option A):** Anti-Liver Kidney Microsomal type 1 antibodies are the hallmark of **Autoimmune Hepatitis (Type 2)**. However, they are also found in a subset of patients with chronic HCV, making it a recognized association. * **Polyarteritis nodosa (Option D):** While PAN is classically and more strongly associated with **Hepatitis B (HBV)**, it has been documented in rare cases of HCV. However, in most competitive exams, if both HBV and HCV are options for PAN, HBV is the primary association. **High-Yield Clinical Pearls for NEET-PG:** * **HCV + Skin:** Porphyria Cutanea Tarda (PCT) and Lichen Planus [1]. * **HCV + Kidney:** Membranoproliferative Glomerulonephritis (MPGN). * **HCV + Endocrine:** Type 2 Diabetes Mellitus and Autoimmune Thyroiditis. * **HCV + Hematology:** B-cell Non-Hodgkin Lymphoma. * **Key Distinction:** Remember **PAN = HBV** and **Cryoglobulinemia = HCV**.

Q: A 6-year-old child presented with perianal pruritus, skin excoriation, and nocturnal enuresis. The child was found to be infected with a parasite causing auto-infection. What is the causative agent?

Enterobius vermicularis. The clinical presentation of **perianal pruritus** (worse at night), skin excoriation from scratching, and **nocturnal enuresis** (bed-wetting) in a child is classic for **Enterobius vermicularis** (Pinworm/Seatworm). **Why Enterobius vermicularis is correct:** The female worm migrates to the perianal region at night to deposit eggs, causing intense itching. **Auto-infection** occurs via the fecal-oral route when a child scratches the area and subsequently ingests the eggs (hand-to-mouth). The irritation can also lead to reflex bladder contractions, manifesting as nocturnal enuresis. Diagnosis is typically made using the **NIH swab** or **Scotch tape test** to visualize eggs. **Why the other options are incorrect:** * **Trichinella spiralis:** Causes trichinosis, characterized by muscle pain (myositis), periorbital edema, and eosinophilia, usually following ingestion of undercooked pork. It does not cause perianal pruritus. * **Giardia lamblia:** A protozoan causing malabsorption, foul-smelling fatty stools (steatorrhea), and bloating. It does not involve the perianal skin or cause enuresis. * **Wuchereria bancrofti:** A nematode causing lymphatic filariasis (elephantiasis). It is transmitted by mosquitoes and presents with lymphadenitis and lymphedema, not perianal symptoms. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Albendazole (single dose, repeated after 2 weeks to kill newly hatched larvae). * **Management Tip:** Always treat the **entire family** simultaneously to prevent reinfection. * **Other parasites causing auto-infection:** *Strongyloides stercoralis*, *Hymenolepis nana*, and *Taenia solium* [1]. * **Morphology:** Eggs are non-bile stained and have a characteristic **D-shape** (planoconvex).

Q: All of the following are features of tetanus, except?

Loss of consciousness occurs in moderately advanced cases. The correct answer is **D**. In Tetanus, the sensorium remains **completely clear** until the very end [1]. The toxin, tetanospasmin, acts on the inhibitory interneurons (Renshaw cells) in the spinal cord and brainstem, but it does not affect the cerebral cortex. Therefore, patients remain fully conscious and alert, which adds to the distress of the painful muscle spasms. Loss of consciousness is not a feature of tetanus unless it occurs as a secondary complication of hypoxia or severe sedation. **Analysis of other options:** * **Option A (Vertebral fractures):** These are a known complication of generalized tetanus. The intense, violent muscular contractions (opisthotonus) can be powerful enough to cause compression fractures of the thoracic vertebrae. * **Option B (Recovery in 4 weeks):** Tetanospasmin binds irreversibly to neuronal receptors. Recovery requires the growth of new axonal nerve terminals, a process that typically takes **3 to 4 weeks**. Survivors usually recover completely unless secondary complications occur. * **Option C (Clinical Diagnosis):** Tetanus is a **clinical diagnosis**. *Clostridium tetani* is rarely recovered from the wound site (only 33% of cases), and its presence does not prove the disease [1]. Serum antitoxin levels are also not helpful for acute diagnosis. **Clinical Pearls for NEET-PG:** * **Pathogenesis:** Retrograde axonal transport of tetanospasmin; cleaves **SNARE proteins** (Synaptobrevin). * **Earliest Sign:** Trismus (Lockjaw) due to masseter spasm. * **Risus Sardonicus:** Characteristic "sneering" grin due to facial muscle spasm. * **Autonomic Dysfunction:** A major cause of death in modern ICUs (labile hypertension, tachycardia, hyperpyrexia). * **Management:** Metronidazole is the preferred antibiotic; Penicillin is avoided as it is a GABA antagonist and may worsen spasms.

Q: Which condition is characterized by risus-sardonicus?

Tetanus. **Explanation:** **Risus sardonicus** (sardonic smile) is a classic clinical sign of **Tetanus**, caused by the neurotoxin *tetanospasmin* produced by *Clostridium tetani* [1]. The toxin blocks the release of inhibitory neurotransmitters (GABA and glycine) from Renshaw cells in the spinal cord. This leads to unopposed muscle contraction. Risus sardonicus specifically results from the characteristic spasm of the facial muscles (masticatory and frontalis muscles), which produces a fixed, grimacing expression with raised eyebrows and an open, "grinning" mouth. **Analysis of Incorrect Options:** * **Rabies:** Characterized by hydrophobia, aerophobia, and laryngeal spasms, but not risus sardonicus. * **Syphilis:** Late-stage neurosyphilis (Tabes dorsalis) involves Argyll Robertson pupils and sensory ataxia, while congenital syphilis may show Hutchinson’s teeth, but facial muscle spasms are not a feature [1]. * **Frost-bite:** Involves localized tissue freezing and necrosis; while it can cause facial stiffness due to cold injury, it does not involve toxin-mediated neurological spasms. **Clinical Pearls for NEET-PG:** * **Trismus (Lockjaw):** Usually the earliest and most common presenting symptom of tetanus. * **Opisthotonus:** A state of severe hyperextension and spasticity in which the individual's head, neck, and spinal column enter into a complete "bridging" or arching position. * **Management:** Treatment involves wound debridement, Metronidazole (preferred over Penicillin G as the latter is a GABA antagonist), and Tetanus Immune Globulin (TIG). * **Autonomic Instability:** A major cause of death in modern intensive care settings for tetanus patients.

Q: Which of the following infections can cause vaginal discharge?

All of the above. Vaginal discharge is a common clinical presentation of various Sexually Transmitted Infections (STIs) [2]. While the discharge typically originates from either the vagina (vaginitis) or the cervix (cervicitis), patients clinically perceive and report both as "vaginal discharge" [1]. 1. **Gonorrhoea (*Neisseria gonorrhoeae*):** This organism primarily causes **cervicitis**. The inflammation of the endocervical mucosa leads to a characteristic **mucopurulent (thick, yellow-green) discharge** [1]. 2. **Chlamydia (*Chlamydia trachomatis*):** Similar to Gonorrhoea, Chlamydia is a major cause of **cervicitis** [3]. It often presents with a mucopurulent discharge and friable cervix (bleeding on contact). It is frequently co-transmitted with Gonorrhoea. 3. **Herpes (HSV-2/HSV-1):** While Herpes is primarily known for painful vesicular or ulcerative lesions, the initial infection often involves the cervix (**herpetic cervicitis**). This inflammation can produce a **watery or mucoid vaginal discharge**, often accompanied by systemic symptoms like fever and inguinal lymphadenopathy. **Clinical Pearls for NEET-PG:** * **Syndromic Management:** Under the NACO guidelines (Kit 1 - Grey), both Gonorrhoea and Chlamydia are treated together using Azithromycin (1g stat) and Cefixime (400mg stat). * **Differential Diagnosis:** Always distinguish cervicitis from **Vaginitis**, which is caused by *Trichomonas vaginalis* (strawberry cervix, frothy discharge), *Candida* (curdy white discharge), or Bacterial Vaginosis (clue cells, fishy odor) [1]. * **Gold Standard:** Nucleic Acid Amplification Test (NAAT) is the investigation of choice for both Chlamydia and Gonorrhoea.

Q: Which of the following conditions is typically seen in late-stage HIV infection?

All of the above. **Explanation:** In HIV infection, clinical manifestations are often categorized by the degree of immunosuppression, typically measured by the CD4+ T-cell count [1]. As the disease progresses to late-stage HIV (AIDS), the immune system becomes severely compromised, leading to a higher prevalence of opportunistic infections and malignancies. **1. Kaposi’s Sarcoma (KS):** This is an AIDS-defining illness caused by Human Herpesvirus 8 (HHV-8) [2]. While it can occur at various CD4 levels, it is most aggressive and commonly seen in late-stage infection (typically CD4 <200 cells/mm³). It presents as violaceous, non-blanching mucosal or cutaneous lesions [2]. **2. Oral Hairy Leukoplakia (OHL):** Caused by the Epstein-Barr Virus (EBV), OHL presents as white, corrugated lesions on the lateral borders of the tongue that cannot be scraped off. It is a highly specific marker of HIV and usually signifies significant immunosuppression (CD4 <200-300 cells/mm³). **3. Gingivitis/Periodontitis:** HIV-associated periodontal diseases, such as Linear Gingival Erythema (LGE) and Necrotizing Ulcerative Periodontitis (NUP), are characteristic of advanced HIV [3]. These conditions involve rapid tissue destruction and are strong clinical indicators of declining immune function. **Conclusion:** Since all three conditions are hallmark clinical features associated with advanced immunosuppression in HIV, **Option D** is the correct answer. **High-Yield NEET-PG Pearls:** * **Most common oral manifestation of HIV:** Oral Candidiasis (Thrush). * **Oral Hairy Leukoplakia vs. Candidiasis:** OHL cannot be scraped off; Candidiasis can be scraped off, leaving an erythematous base. * **CD4 <200:** Threshold for starting PCP prophylaxis (Trimethoprim-Sulfamethoxazole). * **CD4 <50:** High risk for CMV retinitis and Mycobacterium avium complex (MAC).

Q: All of the following are seen in active chronic hepatitis B except?

IgM against core antigen. In Hepatitis B serology, the presence of specific markers distinguishes between acute, chronic, and past infections. This is a high-yield topic for NEET-PG. **Explanation of the Correct Answer:** **Option A (IgM anti-HBc)** is the correct answer because it is a marker of **acute infection** [1]. It appears shortly after HBsAg and persists for about 6 months (the "window period") [1]. In **chronic hepatitis B** (defined by the persistence of HBsAg for >6 months), the immune response shifts from IgM to **IgG** [1]. Therefore, IgM anti-HBc is typically absent in chronic states, unless there is a severe acute flare-up. **Analysis of Incorrect Options:** * **Option B (Total core antibody):** This includes both IgM and IgG. Since IgG anti-HBc persists for life after exposure, total core antibody will be positive in both active chronic and recovered patients [1]. * **Option C (HBeAg):** This is a marker of active viral replication and high infectivity [1]. It is frequently seen in the "active" phase of chronic hepatitis B (HBeAg-positive chronic hepatitis) [1]. * **Option D (HBsAg):** This is the hallmark of any ongoing infection [1]. Its presence for more than 6 months is the defining diagnostic criterion for chronic hepatitis B [1]. **NEET-PG High-Yield Pearls:** 1. **Window Period:** The period where HBsAg and Anti-HBs are both negative; **IgM anti-HBc** is the only diagnostic marker [1]. 2. **Chronic Infection:** Defined by HBsAg (+) for >6 months [1]. 3. **Infectivity:** HBeAg correlates with high viral load and high risk of transmission [1]. 4. **Vaccination:** Only **Anti-HBs** will be positive; all other markers (Core/Envelope) will be negative [1].

Q: Which of the following is NOT a treatment for complications of Herpes Zoster?

Acyclovir. ### Explanation The key to answering this question lies in distinguishing between the **acute treatment** of a viral infection and the **management of its chronic complications**. **1. Why Acyclovir is the correct answer:** Acyclovir is an antiviral agent used to treat the **acute phase** of Herpes Zoster (Shingles) [1]. It works by inhibiting viral DNA polymerase, thereby reducing viral shedding and accelerating the healing of acute skin lesions [3]. However, it is **not** a treatment for the complications of Herpes Zoster, most notably **Post-Herpetic Neuralgia (PHN)**. Once the virus has caused nerve damage leading to chronic pain, antivirals have no therapeutic role [1]. **2. Analysis of Incorrect Options (Treatments for Complications):** * **Amitriptyline (Option B):** A Tricyclic Antidepressant (TCA) considered a first-line agent for PHN. It modulates pain pathways by inhibiting the reuptake of norepinephrine and serotonin. * **Gabapentin (Option C):** An anticonvulsant that binds to the ̡2-̤ subunit of voltage-gated calcium channels. It is a mainstay for neuropathic pain management in PHN. * **Prednisone (Option D):** Corticosteroids are used to treat specific complications like **Ramsay Hunt Syndrome** (to reduce facial nerve edema) or **Zoster Ophthalmicus**. They may also be used in the acute phase to reduce pain and inflammation, though they do not prevent PHN. **Clinical Pearls for NEET-PG:** * **Post-Herpetic Neuralgia (PHN):** Defined as pain persisting for >90 days after the onset of the rash [2]. * **Treatment of Choice for PHN:** Gabapentin, Pregabalin, or TCAs (Amitriptyline). * **Acyclovir Timing:** Most effective when started within **72 hours** of rash onset. * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicating involvement of the nasociliary nerve; a precursor to Zoster Ophthalmicus.

Question 1

Which of the following conditions are associated with Hepatitis C Virus (HCV)?

Accepted Answer

Scleroderma

Answer

Anti-LKM-1 antibody

Answer

Cryoglobulinemia

Answer

Polyarteritis nodosa

Question 2

A 6-year-old child presented with perianal pruritus, skin excoriation, and nocturnal enuresis. The child was found to be infected with a parasite causing auto-infection. What is the causative agent?

Accepted Answer

Enterobius vermicularis

Answer

Trichinella spiralis

Answer

Giardia lamblia

Answer

Wuchereria bancrofti

Question 3

All of the following are features of tetanus, except?

Accepted Answer

Loss of consciousness occurs in moderately advanced cases

Answer

Vertebral fractures

Answer

Survivors recover completely in 4 weeks

Answer

Diagnosis is clinical and no microbiological tests are required

Question 4

An elderly male develops fever 3 days after cholecystectomy. He becomes short of breath, and CXR shows a new right lower lobe infiltrate. Sputum Gram stain shows gram-positive cocci in clumps, and preliminary culture results suggest staphylococci. What is the initial antibiotic of choice?

Accepted Answer

Antibiotic therapy should be based on the incidence of methicillin-resistant staphylococci in that hospital

Answer

Nafcillin

Answer

Vancomycin

Answer

Quinolones are the drug of choice for pneumonia

Question 5

Which condition is characterized by risus-sardonicus?

Accepted Answer

Tetanus

Answer

Rabies

Answer

Syphilis

Answer

Frost-bite

Question 6

Which of the following infections can cause vaginal discharge?

Accepted Answer

All of the above

Answer

Gonorrhoea

Answer

Chlamydia

Answer

Herpes

Question 7

Which of the following conditions is typically seen in late-stage HIV infection?

Accepted Answer

All of the above

Answer

Kaposi's Sarcoma

Answer

Oral hairy leukoplakia

Answer

Gingivitis/periodontitis

Question 8

Kala-azar is not responding to primary treatment. What should be the next line of treatment?

Accepted Answer

Amphotericin-B

Answer

Double dose of antimony

Answer

Ketoconazole

Answer

Splenectomy

Question 9

All of the following are seen in active chronic hepatitis B except?

Accepted Answer

IgM against core antigen

Answer

Total core antibody

Answer

HbeAg

Answer

HbsAg

Question 10

Which of the following is NOT a treatment for complications of Herpes Zoster?

Accepted Answer

Acyclovir

Answer

Amitriptyline

Answer

Gabapentin

Answer

Prednisone

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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