Enteroviruses and parechoviruses — MCQs

10 questions

A 35-year-old woman from San Francisco has been refusing to vaccinate her children due to the claims that vaccinations may cause autism in children. Her 10-year-old male child began developing a low-grade fever with a rash that started on his face; as the rash began to spread to his limbs, it slowly disappeared from his face. When the child was taken to a clinic, the physician noticed swollen lymph nodes behind the ears of the child. Which of the following are characteristics of the virus causing these symptoms?

A 3-year-old boy is brought to the pediatrician by his parents with a presentation of severe diarrhea, vomiting, and fever for the past 2 days. The child is enrolled at a daycare where several other children have had similar symptoms in the past week. On physical exam, the child is noted to have dry mucous membranes. His temperature is 102°F (39°C). Questions regarding previous medical history reveal that the child’s parents pursued vaccine exemption to opt out of most routine vaccinations for their child. The RNA virus that is most likely causing this child’s condition has which of the following structural features?

A 45-year-old man with a history of poorly controlled human immunodeficiency virus (HIV) infection presents to the emergency room complaining of clumsiness and weakness. He reports a 3-month history of worsening balance, asymmetric muscle weakness, and speech difficulties. He recently returned from a trip to Guatemala to visit his family. He has been poorly compliant with his anti-retroviral therapy and his most recent CD4 count was 195. His history is also notable for rheumatoid arthritis and hepatitis C. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 95/min, and respirations are 18/min. On exam, he has 4/5 strength in his right upper extremity, 5/5 strength in his left upper extremity, 5/5 strength in his right lower extremity, and 3/5 strength in his left lower extremity. His speech is disjointed with intermittent long pauses between words. Vision is 20/100 in the left eye and 20/40 in his right eye; previously, his eyesight was 20/30 bilaterally. This patient most likely has a condition caused by which of the following types of pathogens?

A 46-year-old Caucasian male with past medical history of HIV (CD4: 77/mm^3), hypertension, hyperlipidemia, and osteoarthritis presents to the emergency department with sudden weakness of his right hand. He reports that the weakness has gradually been getting worse and that this morning he dropped his cup of coffee. He has never had anything like this happen to him before, although he was hospitalized last year for pneumonia. He reports inconsistent adherence to his home medications, which include raltegravir, tenofovir, emtricitabine, TMP-SMX, hydrochlorothiazide, pravastatin, and occasional ibuprofen. His father died of a myocardial infarction at the age of 60, and his mother suffered a stroke at the age of 72. The patient's temperature is 102.6°F (39.2°C), blood pressure is 156/92 mmHg, pulse is 88/min, and respirations are 18/min. On neurological exam, he has 3/5 strength in the distal muscles of the right extremity with preserved sensation. His neurological exam is normal in all other extremities. Which of the following is the best next step in management?

A virology student is asked to identify a sample of virus. When subjected to a nonionic detergent, which disrupts lipid membranes, the virus was shown to lose infectivity. The student then purified the genetic material from the virus and subjected it to treatment with RNase, an enzyme that cleaves the phosphodiester linkages in the RNA backbone. A minute amount of the sample was then injected into a human cell line and was found to produce viral particles a few days later. Which of the following viruses was in the unknown sample?

An investigator studying patients with symptoms of arthritis detects a nonenveloped virus with a single-stranded DNA genome in the serum of a pregnant patient. Fetal infection with this pathogen is most likely to cause which of the following manifestations?

A 24-year-old man comes to the physician with a 2-day history of fever, crampy abdominal pain, and blood-tinged diarrhea. He recently returned from a trip to Mexico. His temperature is 38.2°C (100.8°F). Abdominal examination shows diffuse tenderness to palpation; bowel sounds are hyperactive. Stool cultures grow nonlactose fermenting, oxidase-negative, gram-negative rods that do not produce hydrogen sulfide on triple sugar iron agar. Which of the following processes is most likely involved in the pathogenesis of this patient's condition?

A 3-day-old female newborn delivered vaginally at 36 weeks to a 27-year-old woman has generalized convulsions lasting 3 minutes. Prior to the event, she was lethargic and had difficulty feeding. The infant has two healthy older siblings and the mother's immunizations are up-to-date. The infant appears icteric. The infant's weight and length are at the 5th percentile, and her head circumference is at the 99th percentile for gestational age. There are several purpura of the skin. Ocular examination shows posterior uveitis. Cranial ultrasonography shows ventricular dilatation, as well as hyperechoic foci within the cortex, basal ganglia, and periventricular region. Which of the following is the most likely diagnosis?

A 31-year-old woman comes to the physician because of a 2-day history of low-grade intermittent fever, dyspnea, and chest pain that worsens on deep inspiration. Over the past 4 weeks, she has had pain in her wrists and the fingers of both hands. During this period, she has also had difficulties working on her computer due to limited range of motion in her fingers, which tends to be more severe in the morning. Her temperature is 37.7°C (99.8°F). Physical examination shows a high-pitched scratching sound over the left sternal border. Further evaluation of this patient is most likely to reveal which of the following findings?

Q10

A previously healthy 24-year-old male is brought to the emergency department because of fevers, congestion, and chest pain for 3 days. The chest pain is exacerbated by deep inspiration. He takes no medications. His temperature is 37.5°C (99.5°F), blood pressure is 118/75 mm Hg, pulse is 130/min, and respirations are 12/min. He appears weak and lethargic. Cardiac examination shows a scratchy sound best heard along the left sternal border when the patient leans forward. There are crackles in both lung bases. Examination of the lower extremities shows pitting edema. Results of a rapid influenza test are negative. EKG shows diffuse ST-elevations with depressed PR interval. An echocardiogram shows left ventricular chamber enlargement with contractile dysfunction. Infection with which of the following pathogens is the most likely cause of this patient's symptoms?

Enteroviruses and parechoviruses US Medical PG Practice Questions and MCQs

Question 1: A 35-year-old woman from San Francisco has been refusing to vaccinate her children due to the claims that vaccinations may cause autism in children. Her 10-year-old male child began developing a low-grade fever with a rash that started on his face; as the rash began to spread to his limbs, it slowly disappeared from his face. When the child was taken to a clinic, the physician noticed swollen lymph nodes behind the ears of the child. Which of the following are characteristics of the virus causing these symptoms?

A. Nonenveloped, DS segmented RNA
B. Enveloped, SS - nonsegmented RNA
C. Enveloped, SS + nonsegmented RNA (Correct Answer)
D. Nonenveloped, SS linear DNA
E. Enveloped, DS linear DNA

Explanation: ***Enveloped, SS + nonsegmented RNA*** - The clinical presentation with a **low-grade fever**, a **rash** that starts on the face and spreads downwards while fading from the face, and **post-auricular lymphadenopathy** is highly characteristic of **Rubella** (German measles). - Rubella virus is an **enveloped**, **single-stranded (SS)**, **positive-sense (+)**, **nonsegmented RNA virus** belonging to the *Togaviridae* family. *Nonenveloped, DS segmented RNA* - This description matches **Rotavirus** (a cause of gastroenteritis) or **Reoviruses**, which are **nonenveloped** and have **double-stranded (DS) segmented RNA** genomes. - These viruses do not cause the described rubella-like symptoms with rash and lymphadenopathy. *Enveloped, SS - nonsegmented RNA* - This describes viruses like **measles, mumps, influenza, and rabies viruses**, which are **enveloped, single-stranded (SS) negative-sense (-) nonsegmented RNA viruses**. - While measles causes a rash, it typically presents with a **high fever**, **Koplik spots**, and a rash that does not fade from the face as it spreads. *Nonenveloped, SS linear DNA* - This description is incorrect as DNA viruses are typically double-stranded. Single-stranded DNA viruses are rare, such as **Parvovirus B19**, which causes **Fifth disease** (erythema infectiosum). - Parvovirus B19 causes a "slapped cheek" rash, which is distinct from the rubella rash described. *Enveloped, DS linear DNA* - This describes viruses such as **Herpesviruses** (e.g., Varicella-Zoster virus causing chickenpox, Herpes Simplex virus) or **Poxviruses**. - While chickenpox involves an enveloped, DS linear DNA virus and a rash, the rash typically presents as **vesicles** and does not have the classic head-to-toe progression with fading on the face.

Question 2: A 3-year-old boy is brought to the pediatrician by his parents with a presentation of severe diarrhea, vomiting, and fever for the past 2 days. The child is enrolled at a daycare where several other children have had similar symptoms in the past week. On physical exam, the child is noted to have dry mucous membranes. His temperature is 102°F (39°C). Questions regarding previous medical history reveal that the child’s parents pursued vaccine exemption to opt out of most routine vaccinations for their child. The RNA virus that is most likely causing this child’s condition has which of the following structural features?

A. Single-stranded, icosahedral, non-enveloped
B. Double-stranded, icosahedral, non-enveloped (Correct Answer)
C. Single-stranded, helical, enveloped
D. Single-stranded, icosahedral, enveloped
E. Double-stranded, helical, non-enveloped

Explanation: ***Double-stranded, icosahedral, non-enveloped*** - The clinical presentation of severe diarrhea, vomiting, and fever in a young child, especially in a daycare setting with a history of vaccine exemption, is highly suggestive of **Rotavirus infection**. - **Rotavirus** is a member of the Reoviridae family and is characterized by its **double-stranded RNA (dsRNA) genome**, **icosahedral capsid**, and **lack of an envelope**. *Single-stranded, icosahedral, non-enveloped* - This describes viruses like **Picornaviruses** (e.g., Poliovirus, Rhinovirus) or **Caliciviruses** (e.g., Norovirus), which can cause gastrointestinal symptoms but lack the dsRNA genome of Rotavirus. - While Norovirus can cause outbreaks of gastroenteritis, the structural features provided do not align with the most likely pathogen given the severity and typical age group for Rotavirus. *Single-stranded, helical, enveloped* - This describes viruses such as **Paramyxoviruses** (e.g., Measles, Mumps) or **Orthomyxoviruses** (e.g., Influenza), which typically cause respiratory or systemic infections, not primarily severe gastroenteritis in this manner. - The presence of an **envelope** and **helical symmetry** rule out Rotavirus. *Single-stranded, icosahedral, enveloped* - This describes viruses such as **Togaviruses** (e.g., Rubella) or **Flaviviruses** (e.g., Dengue), which cause a variety of systemic diseases but are not common causes of severe diarrheal illness in this demographic. - The combination of **enveloped** and an **icosahedral capsid** does not match Rotavirus structure. *Double-stranded, helical, non-enveloped* - While some viruses have **double-stranded RNA**, none of the medically significant viruses are known to be **helical** and **non-enveloped** simultaneously. - **Helical symmetry** is usually associated with enveloped viruses in RNA viruses; therefore, this combination is not characteristic of common human viral pathogens causing gastroenteritis.

Question 3: A 45-year-old man with a history of poorly controlled human immunodeficiency virus (HIV) infection presents to the emergency room complaining of clumsiness and weakness. He reports a 3-month history of worsening balance, asymmetric muscle weakness, and speech difficulties. He recently returned from a trip to Guatemala to visit his family. He has been poorly compliant with his anti-retroviral therapy and his most recent CD4 count was 195. His history is also notable for rheumatoid arthritis and hepatitis C. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 95/min, and respirations are 18/min. On exam, he has 4/5 strength in his right upper extremity, 5/5 strength in his left upper extremity, 5/5 strength in his right lower extremity, and 3/5 strength in his left lower extremity. His speech is disjointed with intermittent long pauses between words. Vision is 20/100 in the left eye and 20/40 in his right eye; previously, his eyesight was 20/30 bilaterally. This patient most likely has a condition caused by which of the following types of pathogens?

A. Arenavirus
B. Bunyavirus
C. Herpesvirus
D. Polyomavirus (Correct Answer)
E. Picornavirus

Explanation: ***Polyomavirus*** - The patient's **poorly controlled HIV**, **low CD4 count (195)**, and progressive neurological symptoms (clumsiness, weakness, speech difficulties, vision changes) are highly suggestive of **Progressive Multifocal Leukoencephalopathy (PML)**. - PML is caused by the **JC virus**, which is a type of **polyomavirus**, typically reactivating in immunocompromised individuals. *Arenavirus* - Arenaviruses (e.g., Lassa fever virus) are known to cause **hemorrhagic fevers** and can lead to neurological complications, but the clinical presentation described (progressive focal neurological deficits in an HIV patient) is not typical for an arenavirus infection. - While some arenaviruses cause **meningoencephalitis**, the progressive, demyelinating-like course seen in this patient points away from arenavirus. *Bunyavirus* - Bunyaviruses (e.g., Hantavirus, La Crosse encephalitis virus) can cause **encephalitis**, fever, and myalgia, but they don't typically present with the specific constellation of **progressive white matter lesions** and focal neurological signs characteristic of PML in an HIV patient. - Hantaviruses are more associated with **hemorrhagic fever with renal syndrome** or **hantavirus cardiopulmonary syndrome**. *Herpesvirus* - While herpesviruses (e.g., HSV, CMV, VZV) can cause severe neurological disease in HIV patients (e.g., **CMV encephalitis**, **HSV encephalitis**, **VZV vasculopathy**), the described progressive multifocal deficits, especially with rapid worsening, in an HIV patient with a low CD4 count strongly favor PML. - Herpesviral encephalitides often present with more acute onset, fever, and seizures, or specific radiographic patterns not directly matching PML. *Picornavirus* - Picornaviruses, such as enteroviruses, can cause **aseptic meningitis** or **encephalitis**, particularly in immunocompromised individuals. - However, the progressive, multifocal neurological deficits, particularly affecting **white matter**, are not characteristic of picornavirus infections, which tend to cause more diffuse or acute inflammatory processes.

Question 4: A 46-year-old Caucasian male with past medical history of HIV (CD4: 77/mm^3), hypertension, hyperlipidemia, and osteoarthritis presents to the emergency department with sudden weakness of his right hand. He reports that the weakness has gradually been getting worse and that this morning he dropped his cup of coffee. He has never had anything like this happen to him before, although he was hospitalized last year for pneumonia. He reports inconsistent adherence to his home medications, which include raltegravir, tenofovir, emtricitabine, TMP-SMX, hydrochlorothiazide, pravastatin, and occasional ibuprofen. His father died of a myocardial infarction at the age of 60, and his mother suffered a stroke at the age of 72. The patient's temperature is 102.6°F (39.2°C), blood pressure is 156/92 mmHg, pulse is 88/min, and respirations are 18/min. On neurological exam, he has 3/5 strength in the distal muscles of the right extremity with preserved sensation. His neurological exam is normal in all other extremities. Which of the following is the best next step in management?

A. Serology for Toxoplasma-specific IgG antibodies
B. Empiric treatment with pyrimethamine-sulfadiazine
C. Head CT (Correct Answer)
D. Empiric treatment with itraconazole
E. Lumbar puncture

Explanation: ***Head CT*** - The patient presents with **focal neurological deficits** (right hand weakness) and has several risk factors, including poorly controlled **HIV with a low CD4 count** (increased risk of opportunistic infections or CNS lesions) and uncontrolled hypertension (increased risk of stroke). A **head CT** is crucial to rapidly identify potential causes like a mass lesion, hemorrhage, or infarct, which would guide immediate management. - The **fever** and **subacute onset** of weakness (gradually worsening with acute exacerbation) also point towards an intracranial process that needs urgent imaging. *Serology for Toxoplasma-specific IgG antibodies* - While **Toxoplasmosis** is a strong consideration given the patient's low CD4 count, **serology alone is not the best initial step** for acute neurological deficits. - A positive IgG indicates past exposure but not necessarily active infection, and it doesn't provide real-time information on the cause of the focal neurological symptoms. Imaging is needed first to identify a lesion. *Empiric treatment with pyrimethamine-sulfadiazine* - This is the treatment for **cerebral toxoplasmosis**, but **empiric treatment should only be initiated after imaging** (CT or MRI) confirms the presence of a lesion consistent with toxoplasmosis, especially in a patient with acute focal deficits. - Starting treatment without imaging may delay diagnosis of other potentially critical conditions like a brain abscess, lymphoma, or stroke. *Empiric treatment with itraconazole* - **Itraconazole** is an antifungal medication, typically used for histoplasmosis, blastomycosis, or aspergillosis, which are less common causes of acute focal neurological deficits in HIV than toxoplasmosis or lymphoma. - There is no specific clinical indication or risk factor (e.g., endemic area for fungal infections) that would make **empiric antifungal treatment** the best next step compared to diagnostic imaging for this presentation. *Lumbar puncture* - A **lumbar puncture** can be useful in diagnosing CNS infections (e.g., cryptococcal meningitis, viral encephalitis) or other inflammatory conditions, but it is typically performed *after* ruling out a mass lesion or increased intracranial pressure with imaging (CT or MRI) to prevent herniation. - Given the patient's focal neurological deficit and potential for a mass or hemorrhage, **LP carries a risk of brain herniation** and is not the best initial step.

Question 5: A virology student is asked to identify a sample of virus. When subjected to a nonionic detergent, which disrupts lipid membranes, the virus was shown to lose infectivity. The student then purified the genetic material from the virus and subjected it to treatment with RNase, an enzyme that cleaves the phosphodiester linkages in the RNA backbone. A minute amount of the sample was then injected into a human cell line and was found to produce viral particles a few days later. Which of the following viruses was in the unknown sample?

A. Togavirus
B. Hepevirus
C. Calicivirus
D. Adenovirus
E. Herpesvirus (Correct Answer)

Explanation: ***Herpesvirus*** - The loss of infectivity with nonionic detergents indicates the presence of a **lipid envelope**, a characteristic of herpesviruses. - The genetic material survived **RNase treatment**, indicating it is **DNA** (not RNA), which is consistent with herpesviruses being DNA viruses. - Under experimental conditions with **direct intracellular injection**, purified herpesvirus DNA can initiate viral replication by utilizing host cell transcription machinery, ultimately producing viral particles. *Togavirus* - Togaviruses are **enveloped RNA viruses**; they would lose infectivity with detergent treatment. - However, their **RNA genome** would have been destroyed by RNase treatment, preventing any subsequent viral particle production. *Hepevirus* - Hepeviruses are **non-enveloped RNA viruses**; they would **not** lose infectivity with nonionic detergent, which contradicts the experimental observation. - Additionally, their **RNA genome** would be destroyed by RNase, preventing viral replication. *Calicivirus* - Caliciviruses are **non-enveloped RNA viruses**, so they would not be inactivated by nonionic detergents. - Their **RNA genome** would be susceptible to degradation by RNase, precluding viral production. *Adenovirus* - Adenoviruses are **non-enveloped DNA viruses**, meaning they would **not lose infectivity** when treated with nonionic detergent, which contradicts the first experimental result. - Although they have a DNA genome that would survive RNase treatment, the lack of envelope rules them out.

Question 6: An investigator studying patients with symptoms of arthritis detects a nonenveloped virus with a single-stranded DNA genome in the serum of a pregnant patient. Fetal infection with this pathogen is most likely to cause which of the following manifestations?

A. Hydrops fetalis (Correct Answer)
B. Notched teeth
C. Microcephaly
D. Chorioretinitis
E. Vesicular rash

Explanation: ***Hydrops fetalis*** - The description of a nonenveloped virus with a **single-stranded DNA genome** is characteristic of **Parvovirus B19**. This virus commonly causes hydrops fetalis due to **fetal anemia** and subsequent heart failure. - Parvovirus B19 infection in pregnant women can lead to severe complications for the fetus, primarily due to tropism for **erythroid progenitor cells**, resulting in anemia. *Notched teeth* - **Hutchinson's teeth**, characterized by notches, are a classic manifestation of **congenital syphilis**, caused by the bacterium *Treponema pallidum*, not a virus. - Syphilis is a spirochete and not a single-stranded DNA virus. *Microcephaly* - **Microcephaly** is a severe neurological abnormality often associated with congenital infections like **Zika virus** or **cytomegalovirus (CMV)**, which are RNA and double-stranded DNA viruses, respectively. - While viral infections can cause microcephaly, Parvovirus B19 is primarily known for causing fetal anemia and hydrops, not typically microcephaly. *Chorioretinitis* - **Chorioretinitis** is a common ocular manifestation of congenital infections such as **toxoplasmosis**, **CMV**, and **rubella**, but it is not a hallmark of Parvovirus B19 infection. - These pathogens have different genomic structures and disease presentations. *Vesicular rash* - A **vesicular rash** is characteristic of infections caused by **herpesviruses**, such as **varicella-zoster virus (VZV)** or herpes simplex virus. - These are **double-stranded DNA viruses**, not single-stranded DNA viruses like Parvovirus B19.

Question 7: A 24-year-old man comes to the physician with a 2-day history of fever, crampy abdominal pain, and blood-tinged diarrhea. He recently returned from a trip to Mexico. His temperature is 38.2°C (100.8°F). Abdominal examination shows diffuse tenderness to palpation; bowel sounds are hyperactive. Stool cultures grow nonlactose fermenting, oxidase-negative, gram-negative rods that do not produce hydrogen sulfide on triple sugar iron agar. Which of the following processes is most likely involved in the pathogenesis of this patient's condition?

A. Dissemination via bloodstream
B. Overactivation of adenylate cyclase
C. Flagella-mediated gut colonization
D. Invasion of colonic microfold cells
E. Inhibition of host cytoskeleton organization (Correct Answer)

Explanation: ***Inhibition of host cytoskeleton organization*** - The patient's symptoms (fever, crampy abdominal pain, blood-tinged diarrhea) and the microbiological findings (**nonlactose fermenting, oxidase-negative, gram-negative rods** that do not produce hydrogen sulfide) are characteristic of **Shigella infection**. - **Shigella** invades colonic epithelial cells and manipulates the host cell's **actin cytoskeleton** through effector proteins (IpaA, IpaB, IpaC) delivered via a **Type III secretion system**. - This cytoskeletal disruption enables **intracellular movement** via actin-based motility and **cell-to-cell spread**, allowing Shigella to evade immune defenses while causing characteristic inflammatory dysentery. *Dissemination via bloodstream* - While some bacterial infections cause bacteremia, **Shigella** infections are typically localized to the **gastrointestinal tract** and do not commonly disseminate systemically via the bloodstream. - **Bacteremia** due to *Shigella* is rare and usually occurs only in immunocompromised individuals or young children with severe disease. *Overactivation of adenylate cyclase* - **Overactivation of adenylate cyclase** producing **cyclic AMP** and leading to **secretory diarrhea** is characteristic of toxins like **cholera toxin** or **heat-labile enterotoxin of E. coli**. - **Shigella** primarily causes **inflammatory dysentery** through mucosal invasion and damage, not through this mechanism of fluid secretion. *Flagella-mediated gut colonization* - Many bacteria use **flagella** for motility and colonization, but **Shigella** species are notably **non-motile** and **lack flagella**. - Their pathogenesis relies on invasion and intracellular spread rather than flagella-driven colonization. *Invasion of colonic microfold cells* - While **Shigella does initially invade through M cells (microfold cells)** in the colonic epithelium to gain entry into the lamina propria, this is just the **initial entry step**, not the primary pathogenic mechanism that causes disease. - The key pathogenic process that leads to the characteristic symptoms is the **disruption of the host cytoskeleton** that enables intracellular replication and lateral spread through epithelial cells, causing the inflammatory dysentery seen in this patient.

Question 8: A 3-day-old female newborn delivered vaginally at 36 weeks to a 27-year-old woman has generalized convulsions lasting 3 minutes. Prior to the event, she was lethargic and had difficulty feeding. The infant has two healthy older siblings and the mother's immunizations are up-to-date. The infant appears icteric. The infant's weight and length are at the 5th percentile, and her head circumference is at the 99th percentile for gestational age. There are several purpura of the skin. Ocular examination shows posterior uveitis. Cranial ultrasonography shows ventricular dilatation, as well as hyperechoic foci within the cortex, basal ganglia, and periventricular region. Which of the following is the most likely diagnosis?

A. Congenital parvovirus infection
B. Congenital Toxoplasma gondii infection (Correct Answer)
C. Congenital Treponema pallidum infection
D. Congenital cytomegalovirus infection
E. Congenital rubella infection

Explanation: ***Congenital Toxoplasma gondii infection*** - **Ventricular dilatation** with widespread **hyperechoic foci** (calcifications) in the brain, along with **posterior uveitis**, highly suggests congenital toxoplasmosis. - Other features like **generalized convulsions**, **icterus**, **purpura**, and **microcephaly** (indicated by 5th percentile weight/length vs 99th percentile head circumference discrepancy suggesting hydrocephalus with macrocephaly) are also consistent with this diagnosis. *Congenital parvovirus infection* - Primarily causes severe **anemia**, **hydrops fetalis**, and **myocarditis**; it does not typically present with extensive cerebral calcifications or uveitis. - While it can lead to neurological issues, the specific brain imaging findings and ocular involvement described are not characteristic. *Congenital Treponema pallidum infection* - Characterized by rhinitis (**snuffles**), **hepatosplenomegaly**, **bone abnormalities** (e.g., osteochondritis), and **rash**. - While it can cause CNS involvement and developmental delays, the distinct pattern of brain calcifications and uveitis is not typical. *Congenital cytomegalovirus infection* - Can cause **periventricular calcifications**, but the widespread, diffuse calcifications (cortex, basal ganglia, periventricular) are less typical than with toxoplasmosis, which often shows more diffuse parenchymal calcifications. - While it shares features like small for gestational age, icterus, and purpura, **posterior uveitis** is more strongly associated with toxoplasmosis. *Congenital rubella infection* - Classic triad includes **cataracts** (or glaucoma), **sensorineural hearing loss**, and **congenital heart defects** (e.g., PDA, pulmonary artery stenosis). - While CNS involvement (e.g., intellectual disability, microcephaly) can occur, the widespread cerebral calcifications and posterior uveitis are not characteristic.

Question 9: A 31-year-old woman comes to the physician because of a 2-day history of low-grade intermittent fever, dyspnea, and chest pain that worsens on deep inspiration. Over the past 4 weeks, she has had pain in her wrists and the fingers of both hands. During this period, she has also had difficulties working on her computer due to limited range of motion in her fingers, which tends to be more severe in the morning. Her temperature is 37.7°C (99.8°F). Physical examination shows a high-pitched scratching sound over the left sternal border. Further evaluation of this patient is most likely to reveal which of the following findings?

A. Mutation of the HFE gene
B. Blood urea nitrogen level > 60 mg/dL
C. Increased titer of anti-citrullinated peptide antibodies (Correct Answer)
D. Coxsackie virus RNA
E. Decreased C3 complement levels

Explanation: ***Increased titer of anti-citrullinated peptide antibodies*** - The patient's symptoms, including **polyarthralgia affecting wrists and fingers, morning stiffness, and pericarditis (pericardial friction rub, chest pain, dyspnea)**, are highly suggestive of **rheumatoid arthritis (RA)**. - **Anti-citrullinated peptide antibodies (ACPA)** are specific and sensitive markers for RA, often present early in the disease and associated with more aggressive forms. *Mutation of the HFE gene* - **HFE gene mutations** are associated with **hereditary hemochromatosis**, a disorder of iron overload. - While hemochromatosis can cause arthropathy, it typically affects larger joints and is not associated with pericarditis or rheumatoid-like morning stiffness. *Blood urea nitrogen level > 60 mg/dL* - A **BUN level > 60 mg/dL** indicates significant **renal dysfunction**, often seen in conditions like **uremia**. - While uremia can cause pericarditis (uremic pericarditis) and sometimes arthralgia, the joint symptoms are not typically inflammatory with morning stiffness, and there's no other evidence of kidney disease. *Coxsackie virus RNA* - **Coxsackievirus infection** can cause **myocarditis and pericarditis**, but it less commonly causes chronic inflammatory polyarthralgia with morning stiffness. - While viral infections can trigger reactive arthritis, the specific presentation here points more strongly to an autoimmune connective tissue disease. *Decreased C3 complement levels* - **Decreased C3 complement levels** are typically seen in immune complex-mediated diseases such as **systemic lupus erythematosus (SLE)**, certain **glomerulonephritides**, and some **bacteremias**. - While SLE can cause polyarthralgia and pericarditis, the absence of other SLE features (e.g., malar rash, photosensitivity, renal involvement, cytopenias) makes RA a more likely primary diagnosis given the specific joint and morning stiffness pattern, though SLE can serologically overlap.

Question 10: A previously healthy 24-year-old male is brought to the emergency department because of fevers, congestion, and chest pain for 3 days. The chest pain is exacerbated by deep inspiration. He takes no medications. His temperature is 37.5°C (99.5°F), blood pressure is 118/75 mm Hg, pulse is 130/min, and respirations are 12/min. He appears weak and lethargic. Cardiac examination shows a scratchy sound best heard along the left sternal border when the patient leans forward. There are crackles in both lung bases. Examination of the lower extremities shows pitting edema. Results of a rapid influenza test are negative. EKG shows diffuse ST-elevations with depressed PR interval. An echocardiogram shows left ventricular chamber enlargement with contractile dysfunction. Infection with which of the following pathogens is the most likely cause of this patient's symptoms?

A. Orthomyxovirus
B. Flavivirus
C. Togavirus
D. Paramyxovirus
E. Picornavirus (Correct Answer)

Explanation: ***Picornavirus*** - This patient presents with **myopericarditis** (concurrent myocarditis and pericarditis), which is particularly characteristic of **picornavirus** infection, specifically **coxsackievirus B**. - **Pericarditis features:** Pleuritic chest pain, pericardial friction rub (scratchy sound), diffuse ST elevations with PR depression on EKG. - **Myocarditis features:** Left ventricular enlargement with contractile dysfunction, signs of heart failure (pitting edema, tachycardia, weakness). - **Coxsackievirus B** is the **most common viral cause** of acute myocarditis and pericarditis in previously healthy young adults, often following a prodrome of respiratory or gastrointestinal symptoms. *Orthomyxovirus* - **Orthomyxoviruses** (influenza virus) can cause myocarditis, but the **negative rapid influenza test** makes this diagnosis unlikely in this case. - While influenza commonly causes respiratory symptoms and fever, the combination of classic pericarditis findings with severe myocarditis points more strongly toward coxsackievirus infection. *Flavivirus* - **Flaviviruses** (e.g., Dengue, Zika, West Nile) typically present with **fever, arthralgias, rash**, or **neurological symptoms**, which are not described here. - Cardiac complications from flaviviruses are rare and would typically occur in the context of their characteristic systemic manifestations. They are not a common cause of acute myopericarditis. *Togavirus* - **Togaviruses** include **rubella virus** and **alphaviruses** (e.g., Chikungunya). Rubella presents with diffuse rash and lymphadenopathy, while alphaviruses cause prominent arthralgias. - While rubella can rarely cause myocarditis, it is not a common cause of acute myopericarditis, and the characteristic rash and joint symptoms are absent in this patient. *Paramyxovirus* - **Paramyxoviruses** include measles, mumps, RSV, and parainfluenza. **Mumps virus** is the paramyxovirus most associated with myocarditis. - However, mumps typically presents with characteristic **parotitis** (parotid gland swelling), which is absent in this patient, making it less likely than coxsackievirus as the cause of this myopericarditis presentation.

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