Cutaneous Amebiasis — MCQs
Amoebic liver abscess can be diagnosed by demonstrating-
Flask-shaped ulcers in the intestine are caused by which of the following?
Amoebic liver abscess most commonly affects which part of the liver?
During water analysis in a hostel, amoebic cysts were seen. The best step to manage it is:
A 6-year-old child is brought with high fever with rigors for 5 days with pain in right hypochondrium. On examination, the patient is anicteric and tenderness is noted in right upper quadrant. What is the best investigation for this case?
Which of the following is the most characteristic diagnostic feature of the trophozoites of Entamoeba histolytica?
Characteristic of amebiasis is:
The most common site for amoebiasis is:
All are used in the treatment of amoebic liver abscess except:
Adult scabies is characterized by which of the following?
Cutaneous Amebiasis Indian Medical PG Practice Questions and MCQs
Question 1: Amoebic liver abscess can be diagnosed by demonstrating-
- A. Trophozoites in the pus (Correct Answer)
- B. Trophozoites in the feces
- C. Cysts in the pus
- D. Cysts in the liver
Explanation: ***Trophozoites in the pus*** - **Amoebic liver abscesses** are caused by the invasive **trophozoite stage** of *Entamoeba histolytica*. - Demonstrating **trophozoites** in the characteristic **'anchovy paste' pus** aspirated from the abscess cavity is diagnostic. *Cysts in the pus* - **Cysts** are the **infective stage** of *Entamoeba histolytica* and are typically found in the **feces**, not in an abscess. - Cysts are responsible for transmission and survival outside the host, but they do not cause invasive disease. *Cysts in the liver* - The disease in the liver is caused by **trophozoites**, which invade the intestinal wall and then spread to the liver. - **Cysts** are never found within the liver parenchyma or abscesses. *Trophozoites in the feces* - While **trophozoites** can be found in the feces during acute amoebic dysentery, their presence alone does not confirm a liver abscess. - Furthermore, **trophozoites** are fragile and often difficult to detect in stool samples, especially once the stool has cooled.
Question 2: Flask-shaped ulcers in the intestine are caused by which of the following?
- A. TB
- B. Giardia
- C. Entamoeba histolytica (Correct Answer)
- D. Typhoid
Explanation: ***Entamoeba histolytica*** - *Entamoeba histolytica* is a protozoan that causes **amoebiasis**, which is characterized by **flask-shaped (bottle-shaped) ulcers** in the colon - this is the **pathognomonic feature** of intestinal amoebiasis. - The trophozoites invade the intestinal mucosa and submucosa, creating a **narrow neck at the mucosal surface** and a **wider base in the submucosa**, giving them their unique flask-like appearance. - These ulcers are most commonly found in the **cecum and ascending colon**. *TB* - Intestinal tuberculosis typically causes **transverse ulcers** (perpendicular to the bowel axis) due to lymphatic spread and caseous necrosis, often in the ileocecal region. - These ulcers are usually associated with **granulomas** and acid-fast bacilli, which are histologically distinct from flask-shaped ulcers. *Giardia* - *Giardia lamblia* (or *intestinalis*) is a flagellate that causes **giardiasis**, primarily adhering to the small intestinal villi and causing malabsorption and diarrhea. - It is **non-invasive** and does not penetrate the intestinal wall or cause ulcer formation; its pathology is mainly due to **mucosal inflammation** and villous blunting. *Typhoid* - Typhoid fever, caused by *Salmonella Typhi*, commonly leads to **longitudinal ulcers** (parallel to the bowel axis) in the **Peyer's patches** of the ileum due to bacterial invasion and necrosis of lymphoid tissue. - These ulcers may perforate but do not present with the flask-shaped morphology characteristic of amoebiasis.
Question 3: Amoebic liver abscess most commonly affects which part of the liver?
- A. Right lobe of liver (Correct Answer)
- B. Left lobe of liver
- C. Portal vein
- D. Right pleural cavity
Explanation: ***Right lobe of liver*** - The **right lobe** of the liver [1] is supplied by a larger proportion of blood from the superior mesenteric and splenic veins, making it more susceptible to parasitic emboli from the bowel. - Due to its larger size and more direct blood supply from the **portal vein**, the right lobe is the most common site (approximately 80-90%) for amoebic liver abscess formation [1]. *Left lobe of liver* - While it can be affected, the **left lobe** is less commonly involved in amoebic liver abscesses compared to the right lobe. - Its blood supply directly from the **portal vein** is less direct and abundant for parasitic entry than that of the right lobe. *Portal vein* - The **portal vein** is the route of entry for *Entamoeba histolytica* cysts from the intestines to the liver, but it is not the site where an abscess forms. - Abscesses form in the **liver parenchyma** [1] after the trophozoites travel via the portal venules and elicit an inflammatory response. *Right pleural cavity* - The **right pleural cavity** is a potential site for complications of a ruptured amoebic liver abscess, leading to **pleural effusion** or **empyema**. - However, it is not the primary site where the amoebic liver abscess itself develops, as it is outside the liver.
Question 4: During water analysis in a hostel, amoebic cysts were seen. The best step to manage it is:
- A. UV Rays
- B. Boiling (Correct Answer)
- C. Chlorination
- D. Iodine
Explanation: **Boiling** - Boiling water at 100°C for at least one minute is highly effective in **killing amoebic cysts**, including *Entamoeba histolytica*, by denaturing their proteins and disrupting their structure. - This method ensures the **destruction of viable cysts**, preventing waterborne transmission of amoebiasis among hostel residents. *UV Rays* - While UV radiation can inactivate many microorganisms, its effectiveness against **amoebic cysts** can be inconsistent, as cysts are more resistant than bacteria or viruses. - The efficacy depends on the **dose and turbidity of the water**, which can shield cysts from UV light. *Chlorination* - **Amoebic cysts are highly resistant to standard chlorine levels** typically used in water disinfection. - Significantly higher doses and longer contact times of chlorine would be required to kill cysts, which may not be practical or safe for drinking water due to the formation of **disinfection byproducts**. *Iodine* - Iodine can kill some pathogens, but its efficacy against **amoebic cysts is variable and often insufficient** at concentrations safe for consumption. - It may not reliably kill all cysts, especially at **lower temperatures or shorter contact times**.
Question 5: A 6-year-old child is brought with high fever with rigors for 5 days with pain in right hypochondrium. On examination, the patient is anicteric and tenderness is noted in right upper quadrant. What is the best investigation for this case?
- A. SGOT/LFT
- B. CECT
- C. Serology
- D. USG (Correct Answer)
Explanation: ***USG*** - A **ultrasound** is the preferred initial investigation, especially in children, for evaluating abdominal pain in the **right hypochondrium** with fever. - It can effectively identify common causes like **cholecystitis**, **hepatitis**, or **liver abscess**, which fit the clinical presentation. *SGOT/LFT* - **Liver function tests (LFTs)** like SGOT/AST and SGPT/ALT provide information about liver inflammation or damage but do not help localize the pathology. - They are useful for assessing liver function but are not the primary diagnostic tool to identify the cause of the pain or fever. *CECT* - **Contrast-enhanced computed tomography (CECT)** is a more advanced imaging technique, often used after initial screening or when ultrasound findings are inconclusive. - It involves radiation exposure and contrast risks, making it less suitable as a first-line investigation for a child with these symptoms. *Serology* - **Serological tests** detect antibodies or antigens related to specific infections (e.g., viral hepatitis) but do not provide immediate anatomical information. - While they can confirm an infectious cause, they cannot identify the source of the pain or rule out other non-infectious pathologies immediately.
Question 6: Which of the following is the most characteristic diagnostic feature of the trophozoites of Entamoeba histolytica?
- A. Shows erythrophagocytosis (Correct Answer)
- B. Has a central karyosome
- C. Nuclear membrane with chromatin
- D. Presence of bacteria outside the cell
Explanation: ***Shows erythrophagocytosis*** - The presence of **engulfed red blood cells** within the cytoplasm (**erythrophagocytosis**) is the **pathognomonic and most diagnostic feature** of **Entamoeba histolytica** trophozoites. - This indicates the amoeba's invasive nature and its ability to damage host tissues, leading to symptoms like **dysentery**. - This feature distinguishes it from non-pathogenic amoebae like *E. dispar* and *E. coli*. *Has a central karyosome* - **Entamoeba histolytica** does have a **small, dot-like, centrally located karyosome** within its nucleus. - However, this feature alone is **not diagnostic** as it is shared with *E. dispar*, which is morphologically identical but non-pathogenic. - Differentiation requires molecular methods or identification of erythrophagocytosis. *Nuclear membrane with chromatin* - **Entamoeba histolytica** trophozoites do have **fine, uniform peripheral chromatin** along the nuclear membrane. - While this is a correct morphological feature, it is **not pathognomonic** and is also present in *E. dispar*. - This helps differentiate from *E. coli* (which has coarse, clumped chromatin) but not from other *Entamoeba* species. *Presence of bacteria outside the cell* - The presence of bacteria outside the cell is an **environmental factor**, not a morphological feature of the trophozoite. - **Entamoeba histolytica** rarely ingests bacteria, preferring red blood cells and host tissue. - In contrast, non-pathogenic *E. coli* commonly ingests bacteria, which can be a distinguishing feature.
Question 7: Characteristic of amebiasis is:
- A. Ulcers with raised margins
- B. Skip lesion
- C. Flask shaped ulcer (Correct Answer)
- D. Longitudinal ulcer
Explanation: ***Flask shaped ulcer*** - The "flask-shaped" ulcer is a **pathognomonic lesion** of intestinal amebiasis, caused by the ***Entamoeba histolytica*** trophozoites invading the colonic mucosa [1]. - This characteristic shape results from the **pinpoint entry** through the mucosa, followed by **lateral extension** and undermining of the submucosa [1]. *Ulcers with raised margins* - Ulcers with **raised, heaped-up margins** are more characteristic of **malignant lesions**, such as neoplastic ulcers in the gastrointestinal tract. - While some inflammatory ulcers can have raised edges, the *distinct* flask shape is specific to amebiasis. *Skip lesion* - **Skip lesions** are discontinuous areas of inflammation, with sections of normal tissue in between affected areas. - This pattern is a hallmark finding in **Crohn's disease**, a type of inflammatory bowel disease, and is not typical of amebic colitis. *Longitudinal ulcer* - **Longitudinal ulcers** (ulcers that run along the length of the bowel) are commonly seen in **inflammatory bowel diseases**, particularly **Crohn's disease**. - They are often associated with fissures and deep ulcerations along the mesenteric border, distinct from the flask shape of amebic ulcers. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Alimentary System Disease, pp. 364-365.
Question 8: The most common site for amoebiasis is:
- A. Sigmoid colon
- B. Transverse colon
- C. Caecum (Correct Answer)
- D. Liver
Explanation: ***Caecum*** - The **caecum** is the most common site for intestinal amoebiasis because it provides an ideal environment for the **trophozoites** of *Entamoeba histolytica* to embed and colonize [1]. - The slower transit time and abundant bacterial flora in the caecum contribute to its susceptibility to **amoebic invasion and ulceration**. *Sigmoid colon* - While the sigmoid colon can be affected by amoebiasis, leading to symptoms like **dysentery**, it is not the initial or most frequent site of colonization [1]. - Involvement of the sigmoid colon typically indicates more widespread or severe intestinal infection. *Transverse colon* - The transverse colon can also be involved in amoebiasis, especially in cases of extensive disease, but it is less commonly the primary site compared to the caecum. - Symptoms related to transverse colon involvement are often diffuse and can include **abdominal pain** and **tenderness**. *Liver* - The **liver** is the most common site for **extraintestinal amoebiasis**, leading to an **amoebic liver abscess** [1]. - However, the question asks for the most common site for amoebiasis in general, implying initial infection, which is typically in the intestine (specifically the caecum).
Question 9: All are used in the treatment of amoebic liver abscess except:
- A. Diloxanide furoate (Correct Answer)
- B. Metronidazole
- C. Emetine
- D. Chloroquine
Explanation: ***Diloxanide furoate*** - This drug is primarily a **luminal amebicide**, meaning it acts in the intestines to eliminate cysts and trophozoites and is used to treat **asymptomatic cyst carriers**. - It is not effective against **extraintestinal forms** of amebiasis, such as an **amebic liver abscess**, where trophozoites are found in tissues. *Metronidazole* - **Metronidazole** is the drug of choice for treating **amebic liver abscess** and other **extraintestinal amebiasis** due to its excellent tissue penetration and amebicidal activity. - It effectively kills **trophozoites** in the liver and other tissues, leading to resolution of the abscess. *Emetine* - **Emetine** (or its derivative, dehydroemetine) is a potent **tissue amebicide** and can be used in the treatment of **amebic liver abscess**, especially when metronidazole is contraindicated or ineffective. - However, its use is limited by significant **cardiotoxicity**, requiring careful monitoring. *Chloroquine* - **Chloroquine** possesses some **amebicidal activity**, particularly against trophozoites in the liver, making it useful as an adjunct or alternative in the treatment of **amebic liver abscess**. - It is often used in combination with other amebicides or in cases where metronidazole alone is insufficient.
Question 10: Adult scabies is characterized by which of the following?
- A. Involvement of palms and soles (Correct Answer)
- B. Involvement of the face
- C. Involvement of the anterior abdomen
- D. All of the above
Explanation: **Explanation:** Scabies is a contagious skin infestation caused by the mite *Sarcoptes scabiei var. hominis*. The distribution of lesions is the most critical diagnostic feature in NEET-PG questions. **1. Why Option A is Correct:** In **adult scabies**, the "Circle of Hebra" defines the classic distribution. This includes the interdigital spaces, wrists, elbows, axillae, periumbilical area, and genitalia. While traditionally taught that palms and soles are spared in adults compared to infants, modern clinical dermatology (and standard textbooks like IADVL) recognizes that **palms and soles** are frequently involved in adults, especially in cases of high mite burden or crusted scabies. Among the given options, it is the most characteristic site of involvement. **2. Why Options B and C are Incorrect:** * **Option B (Face):** The face and scalp are characteristically **spared** in adult scabies. This is because adults have a higher density of sebaceous glands; the sebum is thought to be inhibitory to the mites. Facial involvement is a hallmark of **infantile scabies** or **crusted (Norwegian) scabies**. * **Option C (Anterior Abdomen):** While the periumbilical area is involved, "anterior abdomen" is too broad and less specific than the involvement of the palms/soles or the web spaces. **Clinical Pearls for NEET-PG:** * **Infantile Scabies:** Unlike adults, infants show involvement of the **face, scalp, palms, and soles** with common secondary vesicopustules. * **Pathognomonic Sign:** The **Burrow** (a S-shaped track) is the clinical hallmark, most commonly found on the finger webs and wrists. * **Nocturnal Pruritus:** Itching is worst at night due to a Type IV hypersensitivity reaction to the mite, its eggs, and scybala (feces). * **Treatment of Choice:** Topical **Permethrin (5%)** is the gold standard. Oral Ivermectin (200 µg/kg) is an alternative or adjunct for crusted scabies.
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