Leishmania species US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Leishmania species. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Leishmania species US Medical PG Question 1: A 32-year-old woman presents to your office with abdominal pain and bloating over the last month. She also complains of intermittent, copious, non-bloody diarrhea over the same time. Last month, she had a cough that has since improved but has not completely resolved. She has no sick contacts and has not left the country recently. She denies any myalgias, itching, or rashes. Physical and laboratory evaluations are unremarkable. Examination of her stool reveals the causative organism. This organism is most likely transmitted to the human host through which of the following routes?
- A. Insect bite
- B. Penetration of skin (Correct Answer)
- C. Sexual contact
- D. Inhalation
- E. Animal bite
Leishmania species Explanation: ***Penetration of skin***
- The symptoms of **abdominal pain**, **bloating**, **intermittent copious non-bloody diarrhea**, and a recent **cough** are highly suggestive of a **hookworm infection**.
- Hookworm larvae (filariform larvae) primarily penetrate the skin, usually through bare feet, as their mode of entry into the human host.
*Insect bite*
- Although some parasitic infections are transmitted by insect bites (e.g., malaria, Chagas disease), hookworms are not transmitted this way.
- **Insect-borne diseases** typically present with different clinical manifestations or geographical associations.
*Sexual contact*
- **Sexually transmitted infections** involve direct contact of mucous membranes or body fluids during sexual activity.
- Hookworm infection transmission through sexual contact is not a recognized route.
*Inhalation*
- **Inhalation** is a route of transmission for respiratory pathogens (e.g., influenza, tuberculosis) or certain fungal infections, but not for hookworms.
- While hookworm larvae migrate through the lungs, the initial infection pathway is not via inhalation.
*Animal bite*
- **Animal bites** transmit diseases like rabies or certain bacterial infections, but not parasitic hookworms.
- Hookworm infection does not result from direct contact with an animal's saliva or puncture wound.
Leishmania species US Medical PG Question 2: A 48-year-old man comes to the physician because of a hypopigmented skin lesion on his finger. He first noticed it 4 weeks ago after cutting his finger with a knife while preparing food. He did not feel the cut. For the past week, he has also had fever, fatigue, and malaise. He has not traveled outside the country since he immigrated from India to join his family in the United States 2 years ago. His temperature is 38.7°C (101.7°F). Physical examination shows a small, healing laceration on the dorsal aspect of the left index finger and an overlying well-defined, hypopigmented macule with raised borders. Sensation to pinprick and light touch is decreased over this area. Which of the following is the most likely causal pathogen of this patient's condition?
- A. Epidermophyton floccosum
- B. Mycobacterium leprae (Correct Answer)
- C. Malassezia furfur
- D. Pseudomonas aeruginosa
- E. Leishmania donovani
Leishmania species Explanation: ***Mycobacterium leprae***
- The patient's history of immigration from **India**, a country endemic for leprosy, coupled with the **hypopigmented, anesthetic skin lesion** with raised borders, is classic for **leprosy** (Hansen's disease).
- The diminished sensation to pinprick and light touch in the affected area points to **nerve involvement**, a hallmark of *Mycobacterium leprae* infection.
*Epidermophyton floccosum*
- This fungus primarily causes **tinea infections** (ringworm), such as athlete's foot and jock itch.
- While it can cause skin lesions, they are typically **erythematous** and scaly, not hypopigmented with sensory loss.
*Malassezia furfur*
- This yeast is responsible for **tinea versicolor**, characterized by **hypopigmented or hyperpigmented patches** that typically scale.
- However, it does not cause **nerve damage** or accompanying sensory loss, and systemic symptoms like fever and malaise are not typical.
*Pseudomonas aeruginosa*
- This bacterium can cause various opportunistic infections, including skin infections like **ecthyma gangrenosum** or **folliculitis** in immunocompromised patients.
- *Pseudomonas* infections are usually painful, often associated with a characteristic **grape-like odor**, and do not typically present with chronic, anesthetic, hypopigmented lesions.
*Leishmania donovani*
- This parasite causes **visceral leishmaniasis** (kala-azar), which presents with fever, weight loss, hepatosplenomegaly, and **hyperpigmentation of the skin** (darkening), not hypopigmentation.
- It does not cause localized anesthetic skin lesions like those described in the patient.
Leishmania species US Medical PG Question 3: A 28-year-old woman comes to the emergency department for a rash that began 3 days ago. She has low-grade fever and muscle aches. She has no history of serious illness and takes no medications. She has had 5 male sexual partners over the past year and uses condoms inconsistently. Her temperature is 38.1°C (100.6° F), pulse is 85/min, and blood pressure is 126/89 mm Hg. Examination shows a diffuse maculopapular rash that includes the palms and soles. The remainder of the examination shows no abnormalities. A venereal disease research laboratory (VDRL) test is positive. Which of the following is the next appropriate step in management?
- A. Intravenous penicillin G
- B. Dark field microscopy
- C. Treponemal culture
- D. Oral doxycycline
- E. Fluorescent treponemal antibody absorption test (Correct Answer)
Leishmania species Explanation: ***Fluorescent treponemal antibody absorption test***
- A positive **VDRL** (a non-treponemal test) should be confirmed with a **treponemal-specific test** like the **fluorescent treponemal antibody absorption (FTA-ABS)** test or **Treponema pallidum particle agglutination (TPPA)** assay to definitively diagnose syphilis.
- This confirmatory step helps differentiate true syphilis from false-positive VDRL results, which can occur in autoimmune diseases (SLE, antiphospholipid syndrome), other infections (malaria, mononucleosis), pregnancy, or recent vaccination.
- While this patient's presentation is highly suggestive of **secondary syphilis** (diffuse maculopapular rash involving palms and soles, fever, myalgias, positive VDRL), confirmatory testing is the standard next step before initiating treatment.
- Note: In some clinical settings with classic secondary syphilis, immediate treatment may be initiated, but confirmatory testing remains the most appropriate next diagnostic step.
*Intravenous penicillin G*
- IV aqueous penicillin G is the treatment for **neurosyphilis**, not uncomplicated secondary syphilis.
- **Secondary syphilis** is treated with **intramuscular benzathine penicillin G 2.4 million units** as a single dose.
- Treatment should follow confirmed diagnosis with treponemal-specific testing.
*Dark field microscopy*
- This technique visualizes spirochetes directly from **primary lesions** (chancres) or moist secondary lesions (condyloma lata, mucous patches).
- It is not practical for this patient who has a diffuse maculopapular rash without obvious mucosal or genital lesions.
- Dark-field microscopy requires specialized equipment and expertise not readily available in most emergency departments.
*Treponemal culture*
- **Treponema pallidum** cannot be cultured on artificial media because it is an **obligate pathogen** that requires living host cells.
- Culture is not a diagnostic option for syphilis.
*Oral doxycycline*
- **Doxycycline 100 mg twice daily for 14 days** is an alternative treatment for early syphilis in **penicillin-allergic patients**.
- Treatment should only be initiated after diagnosis is confirmed with treponemal-specific testing.
- This is not the next appropriate step; confirmatory testing comes first.
Leishmania species US Medical PG Question 4: During a humanitarian medical mission in rural Vietnam, a medical resident encounters a 50-year-old man with a year-long history of a pruritic rash on his upper body and face, along with numbness and tingling sensation of both of his palms. He mostly works on his family’s rice farm, where he also takes care of livestock. A physical examination revealed multiple erythematous macules and papules on the face, arms, chest, and back, as well as thinning of the eyebrows and loss of some eyelashes. Additional findings include hypopigmented macules around the elbows, which are insensitive to light touch, temperature, and pinprick. The grip strength is slightly diminished bilaterally with the conservation of both bicipital reflexes. What is the most likely diagnosis?
- A. Leprosy (Correct Answer)
- B. Sporotrichosis
- C. Tinea corporis
- D. Scrofula
- E. Cutaneous leishmaniasis
Leishmania species Explanation: ***Leprosy***
- The combination of a **chronic pruritic rash**, **sensory loss** (numbness, tingling, insensitivity to touch/temperature/pinprick) in hypopigmented macules, **thinning eyebrows**, and **loss of eyelashes (madarosis)** points strongly to leprosy.
- The patient's long-term exposure in a rural, livestock-intensive environment in Vietnam is consistent with areas where **leprosy (Hansen's disease)** is endemic.
- **Peripheral neuropathy** with motor involvement (diminished grip strength) and preserved reflexes is characteristic.
*Sporotrichosis*
- Typically presents as **subcutaneous nodules** or ulcers, often in a **lymphocutaneous pattern**, following a puncture wound.
- While it can occur in agricultural workers, it doesn't usually cause widespread pruritic macules/papules, nerve involvement, or loss of eyebrows/eyelashes.
*Tinea corporis*
- Characterized by **annular, scaly, erythematous patches** with central clearing, often itchy.
- It does not cause sensory deficits, thinning of eyebrows/eyelashes, or hypopigmented, anesthetic lesions.
*Scrofula*
- This refers to **tuberculosis lymphadenitis**, primarily affecting the cervical lymph nodes, causing chronic swelling and sometimes draining sinuses.
- It does not present with a widespread pruritic rash, sensory neuropathy, or characteristic skin lesions like those described in the patient.
*Cutaneous leishmaniasis*
- Causes persistent **skin lesions (papules, nodules, ulcers)**, often with a raised border, typically following a bite from a sandfly.
- While it can be chronic and occur in endemic areas, it generally does not cause sensory nerve damage, eyebrow/eyelash loss, or widespread hypopigmented anesthetic macules.
Leishmania species US Medical PG Question 5: An investigator is studying human genetics and cell division. A molecule is used to inhibit the exchange of genetic material between homologous chromosomes. Which of the following phases of the cell cycle does the molecule target?
- A. Prophase II
- B. Prophase I (Correct Answer)
- C. Metaphase II
- D. Telophase I
- E. Anaphase I
Leishmania species Explanation: ***Prophase I***
- **Crossing over** (genetic recombination) occurs specifically during **Prophase I** of meiosis, particularly during the pachytene stage
- During this phase, homologous chromosomes pair up (synapsis) and exchange genetic material through recombination
- Inhibiting this exchange means targeting the phase where this critical genetic recombination takes place
*Prophase II*
- Prophase II is a stage in meiosis II where chromosomes condense again after a brief interkinesis
- **Crossing over does not occur** in Prophase II - genetic recombination has already been completed in Prophase I
- Homologous chromosomes are no longer paired at this stage
*Metaphase II*
- During Metaphase II, individual chromosomes (not homologous pairs) align along the metaphase plate
- There is **no exchange of genetic material** between homologous chromosomes at this stage
- This phase prepares for the separation of sister chromatids
*Telophase I*
- Telophase I involves decondensation of chromosomes and reformation of nuclear envelopes around the separated homologous chromosomes
- This marks the end of meiosis I, **after** genetic exchange has already occurred in Prophase I
- No crossing over occurs during this phase
*Anaphase I*
- In Anaphase I, **homologous chromosomes separate** and move to opposite poles of the cell
- This phase is characterized by segregation of chromosomes, **not genetic exchange**
- Crossing over has already been completed by this stage
Leishmania species US Medical PG Question 6: A 47-year-old woman comes to the physician because of a 3-day history of fever, fatigue, loss of appetite, cough, and chest pain. Physical examination shows diffuse inspiratory crackles over the left lung field. An x-ray of the chest shows hilar lymphadenopathy and well-defined nodules with central calcifications. Urine studies show the presence of a polysaccharide antigen. A biopsy specimen of the lung shows cells with basophilic, crescent-shaped nuclei and pericellular halos located within macrophages. This patient's history is most likely to show which of the following?
- A. Visit to Arizona desert
- B. Recent trip to Brazil
- C. Previous mycobacterial infection
- D. Exposure to bat droppings (Correct Answer)
- E. Treatment with inhaled glucocorticoids
Leishmania species Explanation: ***Exposure to bat droppings***
- The clinical presentation, including fever, cough, chest pain, **hilar lymphadenopathy**, **nodules with central calcifications**, and **intracellular encapsulated yeasts** in macrophages, is classic for **histoplasmosis**.
- **Histoplasma capsulatum** is endemic to the Ohio and Mississippi River valleys and is transmitted through inhalation of spores from soil contaminated with **bat or bird droppings**.
*Visit to Arizona desert*
- Exposure in the **Arizona desert** is associated with **coccidioidomycosis** (Valley Fever), which presents with similar pulmonary symptoms but is caused by Coccidioides immitis/posadasii, characterized by **spherules** containing endospores.
- While it can cause hilar lymphadenopathy and nodules, the characteristic intracellular budding yeasts within macrophages and the polysaccharide antigen in urine point away from coccidioidomycosis.
*Recent trip to Brazil*
- A trip to **Brazil** might suggest diseases like **Paracoccidioidomycosis**, which presents with chronic mucocutaneous or disseminated lesions, or various tropical infections, but is not typically characterized by the specific pulmonary and microscopic findings described here.
- The histopathological findings of **intracellular yeasts with pericellular halos** (consistent with Histoplasma) would not be the primary finding for paracoccidioidomycosis, which generally shows characteristic **"pilot wheel"** or multiple budding yeasts.
*Previous mycobacterial infection*
- A previous **mycobacterial infection** would lead to tuberculosis, characterized by **acid-fast bacilli** and granulomas with **caseating necrosis**, which is different from the described intracellular yeasts and polysaccharide antigen.
- While tuberculosis can cause hilar lymphadenopathy and pulmonary nodules, the given microscopic description of cells with basophilic nuclei and pericellular halos within macrophages does not fit Mycobacterium tuberculosis.
*Treatment with inhaled glucocorticoids*
- Inhaled glucocorticoids are used to treat conditions like asthma or COPD and, while prolonged use can rarely predispose to **opportunistic fungal infections** (e.g., aspergillosis, candidiasis), they are not a cause of this specific clinical presentation or the microbiological findings of histoplasmosis.
- The use of inhaled steroids would not explain the geographic exposure, hilar lymphadenopathy, or the specific appearance of the fungal elements within macrophages described.
Leishmania species US Medical PG Question 7: A 30-year-old woman who is 24-weeks pregnant presents to the emergency department with fever, painful urination, and headache. The patient's blood pressure is 111/67 mm Hg, the pulse is 95/min, the respiratory rate is 16/min, and the temperature is 38.3°C (101.1°F). Physical examination reveals bilateral tender inguinal lymphadenopathy and painful genital lesions. On closer inspection, the patient’s genital lesions contain clear fluid and measure 5–6 mm in diameter. What is the appropriate description of these lesions?
- A. Pustule
- B. Ulcer
- C. Papule
- D. Bulla
- E. Vesicle (Correct Answer)
Leishmania species Explanation: ***Vesicle***
- A **vesicle** is defined as a **circumscribed, elevated lesion** (macule/papule) containing **clear fluid** and measuring less than 1 cm in diameter.
- The patient's lesions, which are 5-6 mm in diameter and contain clear fluid, perfectly fit the description of vesicles, characteristic of **herpes simplex virus (HSV)** infection.
*Pustule*
- A **pustule** is a small, elevated lesion similar to a vesicle but filled with **pus**, not clear fluid.
- Examples include acne or folliculitis, which are typically opaque and yellowish, unlike the described lesions.
*Ulcer*
- An **ulcer** is a defect or excavation of the skin past the **epidermis**, resulting in the loss of tissue.
- The patient's lesions are described as fluid-filled and elevated, not as an open wound with tissue loss.
*Papule*
- A **papule** is a **solid, elevated lesion** measuring less than 1 cm in diameter.
- While elevated and small, a papule does **not contain fluid**, which is a key characteristic of the described lesions.
*Bulla*
- A **bulla** is a **fluid-filled lesion** that is **larger than 1 cm** in diameter.
- The lesions described are 5-6 mm, making them smaller than the definition of a bulla.
Leishmania species US Medical PG Question 8: A 24-year-old female comes to the physician because of flu-like symptoms and a new rash for 2 days. She denies contacts with sick individuals or recent travel abroad, but recently went camping in Vermont. Vital signs are within normal limits. Examination of the lateral right thigh shows a circular red ring with central clearing. Which of the following is the natural reservoir of the pathogen responsible for this patient's symptoms?
- A. Rat
- B. Rabbit
- C. Tick
- D. Mouse (Correct Answer)
- E. Flea
Leishmania species Explanation: ***Mouse***
- The patient's symptoms, including **flu-like illness** and a **circular red rash with central clearing** (erythema migrans) after camping in Vermont, are classic for **Lyme disease**.
- The causative agent, *Borrelia burgdorferi*, is primarily maintained in **white-footed mice** (genus *Peromyscus*) in its natural reservoir during its larval and nymphal stages.
*Rat*
- While **rats** can carry and transmit various diseases, they are not the primary natural reservoir for *Borrelia burgdorferi*, the pathogen responsible for Lyme disease.
- Diseases associated with rats often include **leptospirosis** and **plague**, which present with different clinical pictures.
*Rabbit*
- **Rabbits** are known reservoirs for diseases like **tularemia** (*Francisella tularensis*), which can cause fever, skin lesions, and lymphadenopathy, but typically not the characteristic **erythema migrans** rash.
- They are not a significant natural reservoir for *Borrelia burgdorferi*.
*Tick*
- The **tick** (specifically *Ixodes scapularis* or **deer tick**) is the **vector** that transmits *Borrelia burgdorferi* to humans, not the natural reservoir.
- The tick acquires the bacteria from infected animal hosts such as mice and deer.
*Flea*
- **Fleas** are vectors for diseases such as **bubonic plague** (*Yersinia pestis*) and **endemic typhus** (*Rickettsia typhi*), which do not manifest with erythema migrans.
- They are not involved in the transmission or natural history of **Lyme disease**.
Leishmania species US Medical PG Question 9: A 27-year-old dental radiographer presented to a clinic with red lesions on his palate, right lower and mid-upper lip, as well as one of his fingers. These lesions were accompanied by slight pain, and the patient had a low-grade fever 1 week before the appearance of the lesions. The patient touched the affected area repeatedly, which resulted in bleeding. Two days prior to his visit, he observed a small vesicular eruption on his right index finger, which merged with other eruptions and became cloudy on the day of the visit. He has not had similar symptoms previously. He did not report drug usage. A Tzanck smear was prepared from scrapings of the aforementioned lesions by the attending physician, and multinucleated epithelial giant cells were observed microscopically. According to the clinical presentation and histologic finding, which viral infection should be suspected in this case?
- A. Herpes simplex infection (Correct Answer)
- B. Varicella-zoster infection
- C. Measles
- D. Herpangina
- E. Hand-foot-and-mouth disease
Leishmania species Explanation: ***Herpes simplex infection***
- The presence of **red lesions on the palate, lips, and finger**, along with **vesicular eruptions** that become cloudy and are accompanied by **pain** and a preceding **low-grade fever**, are classic signs of **herpes simplex virus (HSV) infection**.
- The histological finding of **multinucleated epithelial giant cells** on a **Tzanck smear** is highly characteristic of herpes virus infections, including HSV.
*Varicella-zoster infection*
- While **varicella-zoster virus (VZV)** also causes vesicular lesions and produces multinucleated giant cells, it typically presents with a **widespread rash** (chickenpox) or a **dermatomal distribution** (shingles), which is not described here.
- The patient's initial symptoms are more consistent with **primary herpes simplex infection**, particularly with the localized presentation.
*Measles*
- **Measles** presents with a characteristic **maculopapular rash** that starts on the face and spreads downwards, often preceded by **Koplik spots** in the mouth, and significant **catarrhal symptoms** (cough, coryza, conjunctivitis).
- It does not typically involve vesicular lesions or the presence of multinucleated giant cells on a Tzanck smear.
*Herpangina*
- **Herpangina** is characterized by painful **vesicles and ulcers localized to the posterior oropharynx** (soft palate, tonsillar pillars, uvula), typically caused by Coxsackieviruses.
- It does not usually affect the lips or fingers, and a Tzanck smear would not show multinucleated giant cells.
*Hand-foot-and-mouth disease*
- **Hand-foot-and-mouth disease (HFMD)** is caused by coxsackieviruses and presents with **vesicular lesions** on the **hands, feet, and oral cavity**, particularly the tongue and buccal mucosa.
- While oral lesions are present, the specific involvement of the palate and the characteristic Tzanck smear findings point away from HFMD.
Leishmania species US Medical PG Question 10: A 27-year-old male who works on an organic farm is diagnosed with infection by N. americanus, a helminthic parasite. Eosinophils require which antibody isotype to destroy these parasites via antibody-dependent cellular cytotoxicity?
- A. IgE (Correct Answer)
- B. IgA
- C. IgG
- D. IgM
- E. IgD
Leishmania species Explanation: ***IgE***
- **IgE** antibodies are crucial in the immune response against helminthic parasites, including *N. americanus*, by sensitizing **mast cells** and **eosinophils**.
- When **IgE** binds to the surface of parasites, the **Fc receptor** on eosinophils recognizes the Fc portion of IgE, leading to the release of cytotoxic granules that destroy the parasite (antibody-dependent cellular cytotoxicity).
*IgA*
- **IgA** is primarily found in **mucosal secretions** and plays a role in defending against pathogens at mucosal surfaces, but it is not the primary isotype involved in eosinophil-mediated **ADCC** against helminths.
- While IgA can bind to some immune cells, its main function is to **neutralize toxins** and prevent microbial adhesion at mucosal sites.
*IgG*
- **IgG** is the most abundant antibody in serum and is involved in various immune functions, including **opsonization**, **neutralization**, and **complement activation**.
- Although IgG can mediate ADCC by **NK cells** and **macrophages**, it is not the primary isotype for eosinophil-mediated killing of helminths, which is dominated by IgE.
*IgM*
- **IgM** is typically the first antibody produced during a primary immune response and is very effective at **activating the complement system**.
- Its large pentameric structure also limits its diffusion into tissues, and it does not play a direct role in eosinophil-mediated ADCC against helminthic parasites.
*IgD*
- **IgD** primarily functions as a **B cell receptor** on naive B lymphocytes, signaling for their activation and differentiation.
- It is present in very low concentrations in serum and its role in host defense against parasites or in ADCC is negligible.
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