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?
Q2
A 16-year-old male presents to his pediatrician with a sore throat. He reports a severely painful throat preceded by several days of malaise and fatigue. He has a history of seasonal allergies and asthma. The patient is a high school student and is on the school wrestling team. He takes cetirizine and albuterol. His temperature is 100.9°F (38.3°C), blood pressure is 100/70 mmHg, pulse is 100/min, and respirations are 20/min. Physical examination reveals splenomegaly and posterior cervical lymphadenopathy. Laboratory analysis reveals the following:
Serum:
Na+: 145 mEq/L
K+: 4.0 mEq/L
Cl-: 100 mEq/L
HCO3-: 24 mEq/L
BUN: 12 mg/dL
Ca2+: 10.2 mg/dL
Mg2+: 2.0 mEq/L
Creatinine: 1.0 mg/dL
Glucose: 77 mg/dL
Hemoglobin: 17 g/dL
Hematocrit: 47%
Mean corpuscular volume: 90 µm3
Reticulocyte count: 1.0%
Platelet count: 250,000/mm3
Leukocyte count: 13,000/mm3
Neutrophil: 45%
Lymphocyte: 42%
Monocyte: 12%
Eosinophil: 1%
Basophil: 0%
Which of the following cell surface markers is bound by the pathogen responsible for this patient’s condition?
Q3
A 15-month-old girl is brought to the physician because of a 2-day history of low-grade fever and a painful lesion on her right index finger. She was born at term and has been healthy except for a rash on her upper lip 2 weeks ago, which resolved without treatment. She lives at home with her parents, her 5-year-old brother, and two cats. Her temperature is 38.5°C (101.3°F), pulse is 110/min, respirations are 30/min, and blood pressure is 100/70 mm Hg. A photograph of the right index finger is shown. Physical examination shows tender left epitrochlear lymphadenopathy. Which of the following is the most likely causal organism?
Q4
A previously healthy 16-year-old girl comes to the physician because of fever, fatigue, and a sore throat for 8 days. She also has a diffuse rash that started yesterday. Three days ago, she took amoxicillin that she had at home. She is sexually active with two male partners and uses condoms inconsistently. Her temperature is 38.4°C (101.1°F), pulse 99/min, blood pressure 106/70 mm Hg. Examination shows a morbilliform rash over her trunk and extremities. Oropharyngeal examination shows tonsillar enlargement and erythema with exudates. Tender cervical and inguinal lymphadenopathy are present. Abdominal examination shows mild splenomegaly. A peripheral blood smear shows lymphocytosis with > 10% atypical lymphocytes. Which of the following is most likely to be positive in this patient?
Q5
A 36-year-old woman presents to the emergency department with a 2-day history of conjunctivitis, sensitivity to bright light, and decreased visual acuity. She denies a history of ocular trauma. She wears contact lenses and thought that the contact lenses may be the cause of the symptoms, although she has always used proper hygiene. Fluorescein staining showed a corneal dendritic branching ulcer with terminal bulbs that stained with rose bengal. Giemsa staining revealed multinucleated giant cells. What is the most likely causative agent?
Q6
A 35-year-old male nurse presents to the emergency room complaining of fever and malaise. He recently returned from a medical trip to Liberia to help with a deadly outbreak of a highly infectious disease. He reports severe generalized muscle pain, malaise, fatigue, and a sore throat. He has recently developed some difficulty breathing and a nonproductive cough. His past medical history is notable for asthma. He drinks alcohol socially and does not smoke. His temperature is 102.1°F (38.9°C), blood pressure is 115/70 mmHg, pulse is 115/min, and respirations are 24/min. On examination, a generalized maculopapular rash and bilateral conjunctival injection are noted. Laboratory testing reveals the presence of negative sense, singled-stranded linear genetic material with filaments of varying lengths. The pathogen responsible for this patient’s symptoms is most similar to which of the following?
Q7
An investigator is studying the structural characteristics of pathogenic viruses. Cell cultures infected by different viruses are observed under a scanning electron microscope. One of the cell samples is infected by a virus that has an envelope composed of nuclear membrane molecules. The most likely virus that has infected this cell sample can cause which of the following conditions?
Q8
A 25-year-old G1P0 gives birth to a male infant at 33 weeks’ gestation. The mother immigrated from Sudan one month prior to giving birth. She had no prenatal care and took no prenatal vitamins. She does not speak English and is unable to provide a medical history. The child’s temperature is 101.0°F (38.3°C), blood pressure is 90/50 mmHg, pulse is 140/min, and respirations are 30/min. Physical examination reveals flexed upper and lower extremities, minimal response to stimulation, and slow and irregular respirations. A murmur is best heard over the left second intercostal space. The child’s lenses appear pearly white. Which of the following classes of pathogens is most likely responsible for this patient’s condition?
Q9
A 15-year-old high school rugby player presents to your clinic with a sore throat. He reports that he started feeling fatigued along with body aches about a week ago. His vitals and physical are normal except for an exudative pharynx and an enlarged spleen. Monospot test comes back positive and the student is told not to participate in contact sports for a month. What is the most likely causative agent and which immune cell does it affect?
Q10
A 14-year-old boy is brought to the physician with fever, malaise, and bilateral facial pain and swelling that began 2 days ago. He has no history of serious illness and takes no medications. He was born in India, and his mother received no prenatal care. She is unsure of his childhood vaccination history. He returned from a trip to India 3 weeks ago, where he was visiting his family. His temperature is 38.2°C (100.8°F). There is erythema, edema, and tenderness of the right and left parotid glands. The remainder of the examination shows no abnormalities. Laboratory studies show:
Leukocyte count 13,000/mm3
Hemoglobin 13.0 g/dL
Hematocrit 38%
Platelet count 180,000/mm3
This patient is at greatest risk for which of the following complications?
Viruses US Medical PG Practice Questions and MCQs
Question 1: 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
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.
Question 2: A 16-year-old male presents to his pediatrician with a sore throat. He reports a severely painful throat preceded by several days of malaise and fatigue. He has a history of seasonal allergies and asthma. The patient is a high school student and is on the school wrestling team. He takes cetirizine and albuterol. His temperature is 100.9°F (38.3°C), blood pressure is 100/70 mmHg, pulse is 100/min, and respirations are 20/min. Physical examination reveals splenomegaly and posterior cervical lymphadenopathy. Laboratory analysis reveals the following:
Serum:
Na+: 145 mEq/L
K+: 4.0 mEq/L
Cl-: 100 mEq/L
HCO3-: 24 mEq/L
BUN: 12 mg/dL
Ca2+: 10.2 mg/dL
Mg2+: 2.0 mEq/L
Creatinine: 1.0 mg/dL
Glucose: 77 mg/dL
Hemoglobin: 17 g/dL
Hematocrit: 47%
Mean corpuscular volume: 90 µm3
Reticulocyte count: 1.0%
Platelet count: 250,000/mm3
Leukocyte count: 13,000/mm3
Neutrophil: 45%
Lymphocyte: 42%
Monocyte: 12%
Eosinophil: 1%
Basophil: 0%
Which of the following cell surface markers is bound by the pathogen responsible for this patient’s condition?
A. CD3
B. CD4
C. CD21 (Correct Answer)
D. CD20
E. CD19
Explanation: ***CD21***
- The patient's symptoms (sore throat, fatigue, splenomegaly, posterior cervical lymphadenopathy, and increased lymphocytes) are consistent with **infectious mononucleosis**, which is caused by the **Epstein-Barr virus (EBV)**.
- EBV primarily infects **B lymphocytes** by binding to the **CD21 receptor** (also known as the C3d complement receptor or CR2) on their surface.
*CD3*
- **CD3** is a protein complex found on the surface of **T lymphocytes**, associated with the T-cell receptor.
- EBV primarily targets B cells, not T cells, for initial infection and replication.
*CD4*
- **CD4** is a glycoprotein found on the surface of **helper T cells, monocytes, macrophages, and dendritic cells**.
- It is primarily known as the co-receptor for HIV entry into T cells.
*CD20*
- **CD20** is a transmembrane protein expressed on the surface of **B lymphocytes** from the pre-B cell stage through differentiated B cells, but not on plasma cells.
- While involved in B cell activation and a target for certain immunotherapies, it is not the primary receptor used by EBV for entry.
*CD19*
- **CD19** is another transmembrane glycoprotein expressed on the surface of **B lymphocytes** and is involved in B cell development, activation, and signaling.
- Although it's a B cell marker, **CD21** is the specific receptor that EBV uses for attachment and entry into B cells.
Question 3: A 15-month-old girl is brought to the physician because of a 2-day history of low-grade fever and a painful lesion on her right index finger. She was born at term and has been healthy except for a rash on her upper lip 2 weeks ago, which resolved without treatment. She lives at home with her parents, her 5-year-old brother, and two cats. Her temperature is 38.5°C (101.3°F), pulse is 110/min, respirations are 30/min, and blood pressure is 100/70 mm Hg. A photograph of the right index finger is shown. Physical examination shows tender left epitrochlear lymphadenopathy. Which of the following is the most likely causal organism?
A. Trichophyton rubrum
B. Herpes simplex virus type 1 (Correct Answer)
C. Human papillomavirus type 1
D. Sporothrix schenckii
E. Staphylococcus aureus
Explanation: ***Herpes simplex virus type 1***
- The rash on the upper lip 2 weeks ago suggests a primary **oral HSV-1 infection**, which can be easily transmitted to fingers (herpetic whitlow) through thumb-sucking or touching the mouth.
- The painful lesion on the finger, low-grade fever, and **tender epitrochlear lymphadenopathy** are classic signs of **herpetic whitlow**, a common complication in young children with primary oral HSV infection.
*Trichophyton rubrum*
- This fungus commonly causes **dermatophytosis**, such as athlete's foot (tinea pedis) or nail infections (onychomycosis), which typically present as scaling, itching, or nail discoloration rather than a vesicular, painful lesion with fever and lymphadenopathy.
- While it can infect skin, its presentation is not consistent with sudden onset painful lesion with systemic symptoms and regional lymphadenopathy.
*Human papillomavirus type 1*
- HPV type 1 typically causes **plantar warts** or **common warts**, which are usually benign, non-painful skin growths and do not present with acute inflammation, fever, or lymphadenopathy.
- Warts evolve slowly over time and are not associated with antecedent rash on the lip.
*Sporothrix schenckii*
- This fungus causes **sporotrichosis**, characteristically presenting as multiple painless nodular lesions along lymphatic channels (**lymphocutaneous sporotrichosis**), often following a puncture wound from contaminated plant material.
- Its presentation is typically subacute to chronic, involves a different lesion morphology, and usually lacks the acute febrile illness and prior oral lesions seen here.
*Staphylococcus aureus*
- *S. aureus* can cause various skin infections like **impetigo**, **folliculitis**, or **cellulitis**, often presenting with crusting, pustules, erythema, and warmth.
- While it can cause fever and lymphadenopathy, the vesicular, painful nature of the lesion and the preceding oral rash make HSV-1 a more likely culprit than a primary bacterial infection.
Question 4: A previously healthy 16-year-old girl comes to the physician because of fever, fatigue, and a sore throat for 8 days. She also has a diffuse rash that started yesterday. Three days ago, she took amoxicillin that she had at home. She is sexually active with two male partners and uses condoms inconsistently. Her temperature is 38.4°C (101.1°F), pulse 99/min, blood pressure 106/70 mm Hg. Examination shows a morbilliform rash over her trunk and extremities. Oropharyngeal examination shows tonsillar enlargement and erythema with exudates. Tender cervical and inguinal lymphadenopathy are present. Abdominal examination shows mild splenomegaly. A peripheral blood smear shows lymphocytosis with > 10% atypical lymphocytes. Which of the following is most likely to be positive in this patient?
A. Anti-CMV IgM
B. Flow cytometry
C. ELISA for HIV
D. Throat swab culture
E. Heterophile antibody test (Correct Answer)
Explanation: ***Heterophile antibody test***
- The patient's symptoms (fever, fatigue, sore throat with exudates, generalized rash after amoxicillin, lymphadenopathy, splenomegaly, and **atypical lymphocytes** on blood smear) are classic for **infectious mononucleosis**.
- **Infectious mononucleosis** is most commonly caused by the **Epstein-Barr virus (EBV)**, which is diagnosed by a positive **heterophile antibody test** (Monospot test).
*Anti-CMV IgM*
- While **cytomegalovirus (CMV)** can cause a mononucleosis-like syndrome, it is a less common cause than EBV, and other classic features like diffusely enlarged tender lymph nodes and splenomegaly are more suggestive of EBV.
- CMV mononucleosis typically lacks the prominent **pharyngitis and exudative tonsillitis** seen in EBV infection.
*Flow cytometry*
- **Flow cytometry** is used to identify and quantify specific cell populations, primarily in the diagnosis and monitoring of **hematologic malignancies** (e.g., leukemia, lymphoma).
- It is not a primary diagnostic test for infectious diseases like mononucleosis, though it could rule out other conditions if there was diagnostic uncertainty regarding atypical lymphocytes.
*ELISA for HIV*
- Acute **HIV infection** can present with a mononucleosis-like syndrome and a rash. However, the prominent **exudative tonsillitis** and **atypical lymphocytosis** with definite splenomegaly point more strongly towards EBV.
- While considering the patient's sexual activity, the constellation of symptoms is more directly explained by EBV infection.
*Throat swab culture*
- A **throat swab culture** is primarily used to diagnose bacterial pharyngitis, such as **Streptococcus pyogenes (Group A Strep)**.
- While Group A Strep can cause exudative tonsillitis, it would not typically cause diffuse lymphadenopathy, splenomegaly, a generalized rash (especially after amoxicillin), or atypical lymphocytes.
Question 5: A 36-year-old woman presents to the emergency department with a 2-day history of conjunctivitis, sensitivity to bright light, and decreased visual acuity. She denies a history of ocular trauma. She wears contact lenses and thought that the contact lenses may be the cause of the symptoms, although she has always used proper hygiene. Fluorescein staining showed a corneal dendritic branching ulcer with terminal bulbs that stained with rose bengal. Giemsa staining revealed multinucleated giant cells. What is the most likely causative agent?
A. Candida albicans
B. Acanthamoeba
C. Varicella zoster virus
D. Herpes simplex virus (HSV)-1 (Correct Answer)
E. Pseudomonas
Explanation: ***Herpes simplex virus (HSV)-1***
- The classic **dendritic corneal ulcer with terminal bulbs** revealed by fluorescein staining, coupled with **multinucleated giant cells** on Giemsa staining, is pathognomonic for **herpes simplex keratitis**.
- Though contact lens wear is mentioned, the specific corneal findings point away from typical bacterial keratitis and strongly towards viral etiology.
*Candida albicans*
- Ocular infections with *Candida* typically present as **fungal keratitis**, often with feathery-edged infiltrates and satellite lesions, which differ from the dendritic pattern.
- While contact lens wear can be a risk factor for fungal infections, the specific branching ulcer described is not characteristic of *Candida*.
*Acanthamoeba*
- *Acanthamoeba* keratitis is a severe infection often associated with **contact lens use** and presents with severe pain and a **ring-shaped infiltrate (ring infiltrate)**, rather than a dendritic ulcer.
- *Acanthamoeba* organisms would be identified on microscopy, not multinucleated giant cells.
*Varicella zoster virus*
- While VZV can cause **dendritic ulcers** (similar to HSV), it is typically associated with a history of **shingles (herpes zoster ophthalmicus)**, often with a vesicular rash in the distribution of the trigeminal nerve.
- The absence of a painful vesicular rash and the specific morphology of the dendrite with true terminal bulbs make HSV-1 more likely.
*Pseudomonas*
- **Pseudomonas aeruginosa** is a common cause of bacterial keratitis, particularly in contact lens wearers, and is known for its rapid progression and severe pain.
- It typically causes a **dense, central corneal infiltrate** with a stromal abscess and often hypopyon, which is distinct from a dendritic ulcer.
Question 6: A 35-year-old male nurse presents to the emergency room complaining of fever and malaise. He recently returned from a medical trip to Liberia to help with a deadly outbreak of a highly infectious disease. He reports severe generalized muscle pain, malaise, fatigue, and a sore throat. He has recently developed some difficulty breathing and a nonproductive cough. His past medical history is notable for asthma. He drinks alcohol socially and does not smoke. His temperature is 102.1°F (38.9°C), blood pressure is 115/70 mmHg, pulse is 115/min, and respirations are 24/min. On examination, a generalized maculopapular rash and bilateral conjunctival injection are noted. Laboratory testing reveals the presence of negative sense, singled-stranded linear genetic material with filaments of varying lengths. The pathogen responsible for this patient’s symptoms is most similar to which of the following?
A. Lassa fever virus
B. Hantavirus
C. Dengue virus
D. Lymphocytic choriomeningitis virus
E. Marburg virus (Correct Answer)
Explanation: ***Marburg virus***
- The history of travel to **Liberia** during a deadly outbreak, prolonged fever, malaise, myalgia, respiratory symptoms, and the presence of a **maculopapular rash** and **conjunctival injection** are all highly suggestive of a **viral hemorrhagic fever**.
- The finding of **negative-sense, single-stranded linear genetic material with filaments of varying lengths** points to a **filovirus**, such as the Marburg virus, which causes severe hemorrhagic fever and fits the clinical picture.
*Lassa fever virus*
- While Lassa fever is a **viral hemorrhagic fever endemic to West Africa**, including Liberia, its causative agent, the **Lassa virus**, is an **arenavirus** with a **circular segmented RNA genome**, not filamentous.
- The clinical presentation can be similar, but the genomic characteristic described in the question rules out Lassa virus.
*Hantavirus*
- **Hantaviruses** cause **hemorrhagic fever with renal syndrome** or **hantavirus pulmonary syndrome**, and are primarily found in the **Americas and Asia**, not West Africa.
- They are **bunyaviruses** with a **segmented, tripartite RNA genome**, which does not match the filamentous morphology described.
*Dengue virus*
- **Dengue fever** is a mosquito-borne illness common in **tropical and subtropical regions**, but less likely to be described as a "deadly outbreak of a highly infectious disease" in Liberia of the severity implied here.
- The **dengue virus** is a **flavivirus** with a **single-stranded, positive-sense RNA genome** and an **icosahedral shape**, which differs from the filamentous negative-sense RNA found.
*Lymphocytic choriomeningitis virus*
- **Lymphocytic choriomeningitis virus (LCMV)** is an **arenavirus** that typically causes **aseptic meningitis or meningoencephalitis** and is transmitted via rodents.
- Its genomic characteristics (circular segmented RNA) and typical clinical presentation do not align with the patient's severe, systemic hemorrhagic fever symptoms and the filamentous nature of the pathogen.
Question 7: An investigator is studying the structural characteristics of pathogenic viruses. Cell cultures infected by different viruses are observed under a scanning electron microscope. One of the cell samples is infected by a virus that has an envelope composed of nuclear membrane molecules. The most likely virus that has infected this cell sample can cause which of the following conditions?
A. Ebola
B. Shingles (Correct Answer)
C. Yellow fever
D. Erythema infectiosum
E. Condylomata acuminata
Explanation: ***Shingles***
- The virus causing shingles, **Varicella Zoster Virus (VZV)**, is a **herpesvirus** that acquires its envelope from the **nuclear membrane of the host cell**.
- Herpesviruses bud through the inner nuclear membrane, picking up host nuclear membrane components to form their envelope.
*Ebola*
- Ebola virus is a **filovirus** that acquires its envelope from the **plasma membrane** of the host cell as it buds off.
- Its envelope is not derived from the nuclear membrane.
*Yellow fever*
- Yellow fever is caused by a **flavivirus**, which is an **enveloped RNA virus** that acquires its envelope from the **endoplasmic reticulum** and Golgi apparatus.
- Its envelope is not derived from the nuclear membrane.
*Erythema infectiosum*
- Erythema infectiosum is caused by **Parvovirus B19**, which is a **non-enveloped DNA virus**.
- As it lacks an envelope, it does not bud from any host membrane.
*Condylomata acuminata*
- Condylomata acuminata (genital warts) are caused by **Human Papillomavirus (HPV)**, which is a **non-enveloped DNA virus**.
- Like Parvovirus B19, HPV does not possess an envelope derived from host cell membranes.
Question 8: A 25-year-old G1P0 gives birth to a male infant at 33 weeks’ gestation. The mother immigrated from Sudan one month prior to giving birth. She had no prenatal care and took no prenatal vitamins. She does not speak English and is unable to provide a medical history. The child’s temperature is 101.0°F (38.3°C), blood pressure is 90/50 mmHg, pulse is 140/min, and respirations are 30/min. Physical examination reveals flexed upper and lower extremities, minimal response to stimulation, and slow and irregular respirations. A murmur is best heard over the left second intercostal space. The child’s lenses appear pearly white. Which of the following classes of pathogens is most likely responsible for this patient’s condition?
A. Togavirus (Correct Answer)
B. Retrovirus
C. Protozoan
D. Spirochete
E. Herpesvirus
Explanation: ***Togavirus***
- The combination of **congenital cataracts** (pearly white lenses), **PDA murmur** (left second intercostal space), **prematurity**, and generalized distress in an infant whose mother had no prenatal care points strongly to **congenital rubella syndrome**, caused by the **rubella virus (a Togavirus)**.
- Exposure to rubella during pregnancy, especially in the first trimester, can lead to a triad of **cataracts**, **cardiac defects** (like PDA), and **sensorineural hearing loss**.
*Retrovirus*
- **Retroviruses**, such as HIV, can cause congenital infections but typically present with different symptom complexes, like **immunodeficiency**, **failure to thrive**, and **opportunistic infections**, rather than the classic congenital rubella triad.
- While HIV can cause cardiomyopathy, it doesn't typically cause **cataracts** as a primary congenital defect in the same manner as rubella.
*Protozoan*
- **Protozoans** like **Toxoplasma gondii** can cause congenital infections (**toxoplasmosis**), which typically manifest as **chorioretinitis**, **hydrocephalus**, and **intracranial calcifications**, a different set of symptoms from those described.
- **Toxoplasmosis** does not commonly cause **cataracts** or **patent ductus arteriosus**.
*Spirochete*
- **Spirochetes**, particularly **Treponema pallidum** (causing **congenital syphilis**), can lead to prematurity and other congenital anomalies.
- Symptoms of congenital syphilis often include **maculopapular rash**, **hepatosplenomegaly**, **bone abnormalities**, and **rhinitis**, distinct from the findings in this case.
*Herpesvirus*
- **Herpesviruses** (e.g., CMV, HSV) can cause congenital infections with varied presentations. **Congenital CMV** is associated with **periventricular calcifications**, **microcephaly**, and **sensorineural hearing loss**, while **congenital HSV** typically presents with **skin lesions**, **neurological deficits**, and **ocular manifestations** that are different from the described cataracts.
- While CMV can cause **cataracts**, it's less commonly associated with **PDA** compared to rubella.
Question 9: A 15-year-old high school rugby player presents to your clinic with a sore throat. He reports that he started feeling fatigued along with body aches about a week ago. His vitals and physical are normal except for an exudative pharynx and an enlarged spleen. Monospot test comes back positive and the student is told not to participate in contact sports for a month. What is the most likely causative agent and which immune cell does it affect?
A. Epstein-Barr virus; B-cells (Correct Answer)
B. Group A Streptococcus; Neutrophils
C. Epstein-Barr virus; T-cells
D. Streptococcus; Macrophages
E. Cytomegalovirus; T-cells
Explanation: ***Epstein-Barr virus; B-cells***
- This clinical picture of **fatigue, sore throat (exudative pharyngitis)**, and **splenomegaly** in an adolescent, along with a **positive Monospot test**, is classic for infectious mononucleosis caused by the **Epstein-Barr virus (EBV)**.
- EBV primarily infects **B lymphocytes** by binding to the CD21 receptor, leading to their proliferation and activation.
*Group A Streptococcus; Neutrophils*
- While **Group A Streptococcus (GAS)** can cause exudative pharyngitis, it is not typically associated with **prolonged fatigue** and **splenomegaly**, nor would it result in a **positive Monospot test**.
- GAS is a bacterium and primarily causes an immune response involving **neutrophils** and other innate immune cells, rather than primarily affecting neutrophils directly in the context of persistent infection.
*Epstein-Barr virus; T-cells*
- While EBV infection does lead to a robust **T-cell response** (especially cytotoxic T-cells) to control infected B-cells, its **primary infection and latency site are B-cells**, not T-cells.
- The atypical lymphocytes observed in mononucleosis are largely activated cytotoxic T-cells, but they are responding to B-cell infection.
*Streptococcus; Macrophages*
- **Streptococcus** (a broad term) causes various infections, but the constellation of symptoms including pronounced **fatigue, splenomegaly**, and a **positive Monospot test** is not characteristic of typical streptococcal infections.
- Macrophages are significant in the immune response to bacteria, but they are not the primary cell type directly targeted or dysfunctional in streptococcal infections in the way B-cells are in mono.
*Cytomegalovirus; T-cells*
- **Cytomegalovirus (CMV)** can cause a mononucleosis-like syndrome with symptoms like fatigue and splenomegaly, but the **Monospot test would be negative** in CMV infection.
- CMV primarily infects various cell types including **epithelial cells, fibroblasts, and macrophages**, and can also have tropism for T-cells, but it's not the primary causative agent when a Monospot is positive.
Question 10: A 14-year-old boy is brought to the physician with fever, malaise, and bilateral facial pain and swelling that began 2 days ago. He has no history of serious illness and takes no medications. He was born in India, and his mother received no prenatal care. She is unsure of his childhood vaccination history. He returned from a trip to India 3 weeks ago, where he was visiting his family. His temperature is 38.2°C (100.8°F). There is erythema, edema, and tenderness of the right and left parotid glands. The remainder of the examination shows no abnormalities. Laboratory studies show:
Leukocyte count 13,000/mm3
Hemoglobin 13.0 g/dL
Hematocrit 38%
Platelet count 180,000/mm3
This patient is at greatest risk for which of the following complications?
A. Facial nerve palsy
B. Impaired fertility (Correct Answer)
C. Osteomyelitis of facial bone
D. Glomerulonephritis
E. Diabetes mellitus
Explanation: ***Impaired fertility***
- The patient's symptoms (fever, malaise, **bilateral parotid swelling**) are highly suggestive of **mumps**, especially given his uncertain vaccination status and recent travel.
- In post-pubertal males, mumps can cause **orchitis** (testicular inflammation), a significant risk factor for **impaired fertility** or even sterility due to testicular atrophy.
*Facial nerve palsy*
- While facial nerve issues can theoretically occur with severe parotitis, **facial nerve palsy** is not a common or direct complication of mumps itself.
- More often, facial nerve palsy is associated with conditions like Bell's palsy or tumors of the parotid gland, not typically the acute viral infection seen here.
*Osteomyelitis of facial bone*
- **Osteomyelitis** is an infection of the bone, usually bacterial, and is not a typical complication of mumps.
- There is no clinical evidence (e.g., severe localized pain, skin breakdown, or signs of deep soft tissue infection) to suggest bone involvement.
*Glomerulonephritis*
- **Glomerulonephritis** is an inflammatory kidney condition, sometimes seen post-streptococcal infection or in systemic autoimmune diseases.
- It is not a recognized and common complication of mumps virus infection.
*Diabetes mellitus*
- Mumps can, in rare cases, cause **pancreatitis**, which theoretically could lead to damage to the insulin-producing cells and increase the risk of diabetes.
- However, **impaired fertility** due to orchitis is a much more common and direct complication in post-pubertal males with mumps than diabetes mellitus.
