Myiasis — MCQs
Following are larval control measures, except:
In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
Cutaneous larva migrans is due to ?
A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
Which of the following statements is not correct regarding sebaceous cyst?
Which of the following conditions is characterized by the sign of the groove?
A young female presents with a history of fever and a nodular lesion over the shin. Histopathology reveals foamy histiocytes with neutrophilic infiltration. There is no evidence of vasculitis. What is the most probable diagnosis?
A young tourist presents with an erythematous lesion on the cheek with central crusting after visiting a region endemic for a specific protozoal infection. What is the likely dermatological condition?
What is characteristic of donovanosis?
What is the treatment for Lucio phenomenon?
Myiasis Indian Medical PG Practice Questions and MCQs
Question 1: Following are larval control measures, except:
- A. DDT (Correct Answer)
- B. Gambusia
- C. Intermittent irrigation
- D. Paris green
Explanation: ***DDT*** - **DDT (dichlorodiphenyltrichloroethane)** is primarily classified as an **adulticide** in vector control programs, used mainly for **indoor residual spraying** to kill adult mosquitoes. - While DDT can kill larvae when applied to water, it is **not typically categorized as a larval control measure** in public health practice due to environmental concerns and its primary use against adult vectors. - Its mechanism involves interfering with the **nervous system** of insects, causing paralysis and death. *Paris green* - **Paris green** is a chemical compound historically used as a **larvicide**, particularly effective against **Anopheles larvae** in stagnant water. - It works as a **stomach poison** for larvae when ingested during feeding, making it a specific larval control agent. *Gambusia* - **Gambusia**, also known as **mosquitofish**, are small fish that feed on mosquito larvae, making them a **biological control measure** for larval populations. - They are often introduced into ponds, ditches, and other water bodies to naturally reduce larval numbers. *Intermittent irrigation* - **Intermittent irrigation** is an **environmental manipulation method** that involves draining and refilling water sources at regular intervals, effectively destroying **larval breeding sites**. - This method prevents larvae from completing their development cycle by eliminating the aquatic environment they depend on.
Question 2: In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
- A. Roundworm
- B. Pinworm
- C. Whipworm
- D. Hookworm (Correct Answer)
Explanation: ***Hookworm*** - **Hookworm infection** (Ancylostoma duodenale/Necator americanus) leads to chronic blood loss from the intestines, causing **microcytic hypochromic anemia** and **severe emaciation** due to persistent nutrient loss and malabsorption. - The combination of severe **anemia (Hb 5 g/dL)**, **emaciation**, and **edema** (due to **hypoalbuminemia**, a consequence of protein-losing enteropathy and poor nutrition) is highly characteristic of hookworm infestation in children. - The **discrete rash** on pressure points (knees, ankles, elbows) may represent **ground itch** (pruritic papulovesicular rash at larval penetration sites) or dermatitis secondary to malnutrition and edema. *Roundworm* - **Ascaris lumbricoides** can cause malnutrition and growth delays, but typically does not lead to the severe anemia and edema seen here unless there is a massive infestation leading to intestinal obstruction or biliary obstruction. - Its primary impact is often related to **nutrient competition** and mechanical obstruction, not significant blood loss. *Pinworm* - **Enterobius vermicularis** (pinworm) infection primarily causes **perianal itching**, especially at night. - It does not typically cause systemic symptoms like **severe anemia**, **emaciation**, or **edema**, as it does not feed on blood or cause significant nutrient malabsorption. *Whipworm* - **Trichuris trichiura** (whipworm) can cause chronic dysentery, **rectal prolapse**, and **anemia** in heavy infections due to blood loss. - While it can contribute to **growth retardation** and anemia, it is less likely to cause the profound emaciation and edema described compared to hookworm, especially with a hemoglobin level of 5 g/dL, which points strongly to major chronic blood loss.
Question 3: Cutaneous larva migrans is due to ?
- A. W.bancrofti
- B. B. Malayi
- C. D. medinensis
- D. Ancylostoma braziliense (Correct Answer)
Explanation: ***Ancylostoma braziliense*** - **Cutaneous larva migrans** is primarily caused by the larvae of **dog and cat hookworms**, especially *Ancylostoma braziliense*. - Humans become **accidental hosts** when these larvae penetrate the skin but cannot complete their life cycle, leading to **serpiginous tracks**. *W. bancrofti* - This parasite, **Wuchereria bancrofti**, is a filarial nematode that causes **lymphatic filariasis** (elephantiasis). - Its effects are characterized by **lymphedema** and **hydrocele**, not migrating skin lesions. *B. Malayi* - **Brugia malayi** is another filarial nematode responsible for **lymphatic filariasis** in humans, similar to *W. bancrofti*. - It primarily causes **swelling of the limbs** and scrotum, not cutaneous larva migrans. *D. medinensis* - **Dracunculus medinensis** is the parasite that causes **dracunculiasis**, also known as **Guinea worm disease**. - This infection is characterized by a **painful blister** and subsequent emergence of the adult worm, which is distinct from creeping eruptions.
Question 4: A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
- A. Loa loa
- B. Diphyllobothrium latum
- C. Dermatobia hominis (Correct Answer)
- D. Dracunculus medinensis
Explanation: ***Dermatobia hominis*** - The description of **cutaneous nodules** with a central pore from which a **moving larva** is observed, particularly after travel to a tropical region like Belize, is classic for **furuncular myiasis** caused by **Dermatobia hominis** larvae (human botfly). - The **"occasional stinging"** and **"dark exudate"** are characteristic symptoms of the larva burrowing in the skin and secreting waste products. *Loa loa* - **Loa loa** (African eye worm) is a filarial nematode that migrates through **subcutaneous tissues** and occasionally across the eye, causing **Calabar swellings**. - It does not present as a **furuncular lesion** with a visible central moving larva emerging from a pore. *Diphyllobothrium latum* - **Diphyllobothrium latum** is a **tapeworm** that infects the intestines and is acquired by consuming undercooked infected fish. - It causes gastrointestinal symptoms and can lead to **vitamin B12 deficiency**, but it does not produce **skin lesions with moving larvae**. *Dracunculus medinensis* - **Dracunculus medinensis** (guinea worm) infection typically results in a **painful blister** on the lower limbs, from which the female worm emerges to release larvae when exposed to water. - While it involves a skin lesion, the presentation of **multiple nodules with a central pore revealing a moving larva** is not consistent with **dracunculiasis**.
Question 5: Which of the following statements is not correct regarding sebaceous cyst?
- A. Found on hairy areas of the body
- B. Treatment is incision and drainage (Correct Answer)
- C. Not found on palms and soles
- D. It has a punctum
Explanation: ***Treatment is incision and drainage*** - The standard treatment for a sebaceous cyst (more accurately an **epidermoid cyst** or **pilar cyst**) is **surgical excision** of the entire cyst wall to prevent recurrence. - **Incision and drainage** only provides temporary relief by emptying the contents but leaves the cyst wall intact, leading to a high chance of the cyst refilling. *Found on hairy areas of the body* - This statement is generally correct as sebaceous cysts often arise from hair follicles and are common in **hair-bearing areas** like the scalp, face, neck, and trunk. - They occur due to the accumulation of **sebum** and keratin within a blocked or damaged sebaceous gland or hair follicle. *Not found on palms and soles* - This statement is correct because **palms and soles** generally **lack sebaceous glands** and hair follicles, hence sebaceous cysts are typically not found in these locations. - Cysts found in these areas are more likely to be **ganglion cysts** or other types of epidermal inclusion cysts. *It has a punctum* - This statement is often correct; many sebaceous cysts (especially epidermoid cysts) have a visible **central punctum** which represents the occluded pore from which the cyst originated. - This punctum is a **key diagnostic feature** and can sometimes exude a cheesy, foul-smelling material.
Question 6: Which of the following conditions is characterized by the sign of the groove?
- A. Lymphogranuloma venereum (Correct Answer)
- B. Granuloma inguinale
- C. Syphilis
- D. Chancroid
Explanation: **Explanation:** **Lymphogranuloma venereum (LGV)** is caused by the **L1, L2, and L3 serovars of *Chlamydia trachomatis***. The "Sign of the Groove" (Greenblatt’s sign) is a pathognomonic clinical finding in the secondary stage of LGV. It occurs when the inguinal and femoral lymph nodes enlarge simultaneously, separated by the rigid **inguinal ligament**. This creates a visible depression or "groove" between the two groups of inflamed lymph nodes. **Analysis of Incorrect Options:** * **B. Granuloma Inguinale (Donovanosis):** Caused by *Klebsiella granulomatis*. It presents with painless, beefy-red, velvety ulcers. It is characterized by "pseudobuboes" (subcutaneous granulation tissue) rather than true lymphadenopathy. * **C. Syphilis:** Primary syphilis presents with a painless, indurated "hard chancre." While it causes bilateral inguinal lymphadenopathy, the nodes are discrete, rubbery, and do not form a groove. * **D. Chancroid:** Caused by *Haemophilus ducreyi*. It presents with painful, soft ulcers and painful inflammatory buboes that are usually unilateral and may suppurate, but they do not form the characteristic groove sign. **High-Yield Clinical Pearls for NEET-PG:** * **Stages of LGV:** Primary (painless papule/ulcer), Secondary (Inguinal syndrome with the Groove sign), and Tertiary (Genito-anorectal syndrome/Elephantiasis). * **Diagnosis:** Frei test (historical), NAAT (current gold standard), and **Donovan bodies** (safety-pin appearance) are seen in Donovanosis, NOT LGV. * **Treatment:** Doxycycline (100 mg BID for 21 days) is the drug of choice for LGV.
Question 7: A young female presents with a history of fever and a nodular lesion over the shin. Histopathology reveals foamy histiocytes with neutrophilic infiltration. There is no evidence of vasculitis. What is the most probable diagnosis?
- A. Sweet's Syndrome
- B. Erythema nodosum (Correct Answer)
- C. Erythema nodosum leprosum
- D. Behcet's syndrome
Explanation: ### Explanation **Correct Answer: B. Erythema nodosum** **Why it is correct:** Erythema nodosum (EN) is the most common form of **septal panniculitis**. Clinically, it presents as tender, erythematous nodules typically located over the **pretibial area (shins)**, often accompanied by fever and malaise. Histopathologically, early lesions show edema and neutrophilic infiltration of the septa. As the lesion evolves, it is characterized by **Miescher’s radial granulomas**—small clusters of spindle-shaped or **foamy histiocytes** surrounding a central cleft. The absence of vasculitis is a hallmark feature that distinguishes EN from other forms of panniculitis. **Why the other options are incorrect:** * **A. Sweet’s Syndrome:** This is a neutrophilic dermatosis characterized by "juicy" erythematous plaques and high fever. Histology shows dense dermal neutrophilic infiltrate with papillary dermal edema, but it is not a primary panniculitis and does not typically present with foamy histiocytes in the septa. * **C. Erythema nodosum leprosum (ENL):** While ENL also presents with tender nodules and fever, it is a Type 2 Lepra reaction. Histologically, it is a **lobular panniculitis** and, crucially, it **must show evidence of vasculitis** (leukocytoclastic vasculitis) and the presence of *M. leprae* (AFB positive). * **D. Behcet’s syndrome:** While it can cause EN-like lesions, the systemic involvement (oral/genital ulcers, uveitis) and the characteristic histopathology (often showing vasculitis) do not fit the isolated description provided. **NEET-PG High-Yield Pearls:** * **Most common cause of EN:** Idiopathic (followed by Streptococcal infections, Sarcoidosis, and TB). * **Histopathology Key:** Septal panniculitis **without** vasculitis = Erythema Nodosum. * **Löfgren Syndrome:** Triad of EN, bilateral hilar lymphadenopathy, and arthritis (highly suggestive of Sarcoidosis). * **Miescher’s Radial Granulomas:** Pathognomonic histological finding for EN.
Question 8: A young tourist presents with an erythematous lesion on the cheek with central crusting after visiting a region endemic for a specific protozoal infection. What is the likely dermatological condition?
- A. Cutaneous Leishmaniasis (Correct Answer)
- B. Systemic Lupus Erythematosus
- C. Lupus vulgaris
- D. Chilblains
Explanation: ### Explanation **Correct Option: A. Cutaneous Leishmaniasis** Cutaneous Leishmaniasis (CL), often referred to as "Oriental Sore" or "Delhi Boil," is caused by the protozoan *Leishmania* species and transmitted by the bite of an infected **female sandfly (*Phlebotomus*)**. The classic presentation begins as a small erythematous papule at the inoculation site (usually exposed areas like the face), which evolves into a nodule and eventually develops **central crusting** or ulceration with a raised, indurated border. The history of travel to an endemic region is a crucial diagnostic clue. **Why Incorrect Options are Wrong:** * **B. Systemic Lupus Erythematosus (SLE):** Typically presents with a "malar rash" (butterfly distribution) that spares the nasolabial folds. It is an autoimmune condition, not associated with travel to protozoal endemic areas or central crusting. * **C. Lupus Vulgaris:** This is a chronic form of cutaneous tuberculosis. While it affects the face, it typically presents as "apple-jelly" nodules on diascopy and follows a very chronic, progressive course rather than an acute post-travel presentation. * **D. Chilblains (Pernio):** An inflammatory response to cold, damp conditions. It presents as itchy, purple-red bumps on fingers or toes, not as a crusted facial lesion following tropical travel. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Female Sandfly (*Phlebotomus*). * **Diagnosis:** Skin biopsy or slit-skin smear showing **LD bodies** (Leishman-Donovan bodies) within macrophages. * **Treatment of Choice:** Intralesional or systemic **Sodium Stibogluconate** (Pentavalent antimonials) or Miltefosine. * **Volcano Sign:** The appearance of a crusted ulcer with a central pit is often described as the "volcano sign."
Question 9: What is characteristic of donovanosis?
- A. Pseudolymphadenopathy (Correct Answer)
- B. Penicillin is used for treatment
- C. Painful ulcer
- D. Suppurative lymphadenopathy
Explanation: **Donovanosis (Granuloma Inguinale)** is a chronic, progressive bacterial infection caused by the intracellular Gram-negative organism *Klebsiella granulomatis*. ### **Explanation of the Correct Answer** **A. Pseudolymphadenopathy:** This is the hallmark of Donovanosis. Unlike other STIs, the infection does not typically involve the regional lymph nodes. Instead, the subcutaneous granulation tissue spreads along the inguinal folds, causing firm, non-tender swellings that mimic enlarged lymph nodes. These are called **"pseudobuboes."** ### **Why Other Options are Incorrect** * **B. Penicillin is used for treatment:** Penicillin is ineffective. The CDC-recommended first-line treatment is **Azithromycin** (1g weekly or 500mg daily for at least 3 weeks). * **C. Painful ulcer:** Donovanosis is classically **painless**. It presents as beefy-red, friable (bleeds easily on touch) ulcers with rolled-out edges. Pain only occurs if there is secondary bacterial superinfection. * **D. Suppurative lymphadenopathy:** This is characteristic of **Lymphogranuloma Venereum (LGV)** or **Chancroid**, where true fluctuant buboes form. Donovanosis lacks true lymph node involvement. ### **High-Yield Clinical Pearls for NEET-PG** * **Donovan Bodies:** Diagnosis is confirmed by seeing "safety-pin" appearing organisms within large macrophages on a Giemsa or Wright stain (crush smear). * **Clinical Appearance:** Often described as "beefy-red" granulation tissue with a "velvety" texture. * **Extragenital Involvement:** Can occur in the mouth, liver, or bone via autoinoculation or hematogenous spread. * **Mnemonic:** Remember the **"4 Ps"** of Donovanosis: **P**ainless, **P**rogressive, **P**seudobuboes, and **P**olymorphic (various clinical types like ulcerogranulomatous, hypertrophic, etc.).
Question 10: What is the treatment for Lucio phenomenon?
- A. Steroids
- B. Lenalidomide
- C. Clofazimine
- D. Exchange transfusion (Correct Answer)
Explanation: **Explanation:** **Lucio Phenomenon** is a rare, life-threatening variant of Type 2 Lepra Reaction (ENL) seen exclusively in patients with diffuse lepromatous leprosy (Lucio leprosy). It is characterized by necrotizing vasculitis of small vessels, leading to extensive, jagged, purpuric macules and large areas of skin necrosis. 1. **Why Exchange Transfusion is Correct:** The pathogenesis involves severe hypercoagulability, immune complex deposition, and massive bacterial load leading to vascular occlusion. **Exchange transfusion** (or plasmapheresis) is considered the treatment of choice in severe, life-threatening cases because it rapidly removes circulating immune complexes, inflammatory cytokines, and helps correct the underlying coagulopathy. 2. **Why Other Options are Incorrect:** * **Steroids (A):** While used in standard ENL, they are often insufficient as monotherapy for Lucio phenomenon due to the primary mechanism being thrombotic infarct rather than simple inflammation. * **Lenalidomide (B):** This is a derivative of Thalidomide. While Thalidomide is the drug of choice for standard ENL, it is notably **ineffective** in Lucio phenomenon. * **Clofazimine (C):** It has anti-inflammatory properties used in chronic ENL but acts too slowly to manage the acute, necrotic crisis of Lucio phenomenon. **Clinical Pearls for NEET-PG:** * **Geographic association:** Most common in Mexico and Central America. * **Clinical hallmark:** "Median-sized" necrotic ulcers with a jagged border. * **Histopathology:** Shows colonization of endothelial cells by *M. lepromatosis* or *M. leprae*, resulting in endothelial proliferation and thrombosis. * **Key distinction:** Unlike ENL, Lucio phenomenon typically lacks systemic symptoms like high fever in the early stages, focusing instead on cutaneous infarcts.
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