Infectious Diseases Practice Questions

Q: An 8-month-old girl presented with sudden onset of high fever (103 extdegree F). Despite the absence of signs of upper respiratory tract infection, meningitis, or encephalitis, her fever escalated to 105 extdegree F, leading to a febrile seizure. Upon examination by the pediatrician, the child's temperature had subsided, and a generalized papular rash was noted. What is the most likely diagnosis?

Roseola infantum caused by human herpes virus 6. ### Explanation The clinical presentation described is classic for **Roseola Infantum** (also known as Exanthem Subitum or Sixth Disease). **1. Why the Correct Answer is Right:** Roseola infantum, caused primarily by **Human Herpesvirus 6 (HHV-6)**, typically affects infants aged 6–15 months. The hallmark of this condition is a **sudden high fever** (often >103°F) lasting 3–5 days in an otherwise well-appearing child. As the fever abruptly subsides (**defervescence**), a rose-pink, maculopapular rash appears, starting on the trunk and spreading to the face and extremities. The rapid rise in temperature makes Roseola the most common cause of **febrile seizures** in this age group. **2. Why Other Options are Incorrect:** * **Erythema Infectiosum (Parvovirus B19):** Characterized by a "slapped-cheek" appearance followed by a reticular (lace-like) rash on the body. It lacks the preceding high fever and sudden defervescence pattern. * **Hand-Foot-and-Mouth Disease (Coxsackievirus A16):** Presents with vesicular eruptions on the palms, soles, and oral mucosa (herpangina), rather than a generalized post-febrile papular rash. * **Measles (Morbillivirus):** Presents with the "3 Cs" (Cough, Coryza, Conjunctivitis) and Koplik spots. Crucially, in measles, the rash appears **while the fever is at its peak**, not after it disappears. **3. NEET-PG High-Yield Pearls:** * **Nagayama Spots:** Erythematous papules on the soft palate and uvula seen in some Roseola patients. * **HHV-6 Pathogenesis:** It infects T-lymphocytes (CD4+ cells). * **Sequence is Key:** Fever **THEN** Rash = Roseola. Fever **WITH** Rash = Measles/Rubella. * **Treatment:** Supportive; ganciclovir is reserved only for severe immunocompromised cases.

Q: What is the most fatal complication of measles?

Subacute sclerosing panencephalitis (SSPE). **Explanation:** The correct answer is **Subacute sclerosing panencephalitis (SSPE)**. SSPE is a rare, progressive, and chronic inflammatory neurological disease caused by a persistent infection with a mutant strain of the measles virus. It typically manifests **7–10 years** after the initial measles infection. It is considered the **most fatal complication** because it is universally lethal; there is no known cure, and it leads to progressive cognitive decline, myoclonic jerks, and eventually death. **Analysis of Incorrect Options:** * **Pneumonia:** This is the **most common cause of death** from measles in children and the most common overall complication. However, while it causes more total deaths due to its frequency, it is not as "fatal" (in terms of case-fatality rate) as SSPE, which has a 100% mortality rate. * **Otitis Media:** This is the **most common complication** of measles overall, but it is rarely life-threatening. * **Polyps:** These are not a recognized complication of measles infection. **NEET-PG High-Yield Pearls:** * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia (Hecht’s Giant Cell Pneumonia). * **SSPE Diagnosis:** Look for high titers of anti-measles antibodies in the CSF and serum (intrathecal synthesis) and **periodic complexes** on EEG. * **Vitamin A:** Supplementation reduces the severity and mortality of measles in children. * **Koplik spots:** Pathognomonic enanthem found on the buccal mucosa opposite the lower second molars during the pre-eruptive stage.

Q: An 8-year-old boy presented with a 4-day history of swelling on both sides of the face, below the ears. The swelling first started on the left side and then appeared on the right side 3 days later. What is the most likely diagnosis?

Epidemic parotitis. **Explanation:** The clinical presentation of an 8-year-old child with acute, sequential, bilateral swelling of the parotid glands (below the ears) is classic for **Epidemic Parotitis**, commonly known as **Mumps**. **Why the correct answer is right:** Mumps is a viral infection caused by the *Rubulavirus* (Paramyxoviridae family). It typically affects children and is characterized by a prodrome of fever and malaise, followed by parotid swelling. A key diagnostic feature is the **asymmetrical progression**: it often starts on one side and involves the contralateral side within 2–3 days. The swelling displaces the earlobe upward and outward, which matches the description in the question. **Why incorrect options are wrong:** * **Bacterial Sialadenitis:** Usually presents as a **unilateral**, extremely painful, erythematous swelling. It is often associated with purulent discharge from Stensen’s duct and high-grade fever, unlike the typical viral course of Mumps. * **Sialadenosis:** This refers to non-inflammatory, non-neoplastic enlargement of the salivary glands, usually associated with systemic conditions like diabetes, alcoholism, or malnutrition. It is chronic and painless, not acute. * **Sialadenitis:** This is a general term for inflammation of the salivary gland. While Mumps is a form of viral sialadenitis, "Epidemic Parotitis" is the specific clinical diagnosis for this presentation in a pediatric population. **Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis (usually unilateral; rarely leads to infertility). * **Diagnosis:** Primarily clinical; confirmed by IgM antibodies or PCR. * **Amylase:** Serum amylase levels are often elevated in Mumps due to salivary gland involvement. * **Prevention:** Live attenuated vaccine (MMR/MMRV).

Q: All of the following statements regarding measles are true except?

Rash appears first on the leg. **Explanation:** The correct answer is **A (Rash appears first on the leg)** because it is a false statement. In Measles (Rubeola), the characteristic maculopapular rash follows a **cephalocaudal progression**. It typically appears first behind the ears and along the hairline, spreading downwards to the face, neck, trunk, and finally reaching the extremities (legs) by the third day. **Analysis of other options:** * **Option B:** **Koplik spots** are pathognomonic for measles. They are small, bluish-white grains on an erythematous base found on the buccal mucosa opposite the lower second molars during the pre-eruptive (prodromal) stage. * **Option C:** **SSPE** is a rare, progressive, and fatal demyelinating disease of the central nervous system that occurs 5–10 years after a primary measles infection due to the persistence of a mutant virus. * **Option D:** Measles is caused by an **RNA virus** belonging to the genus *Morbillivirus* of the family *Paramyxoviridae*. **High-Yield Clinical Pearls for NEET-PG:** * **Infectivity:** Highly contagious from 4 days before to 5 days after the appearance of the rash. * **Vitamin A:** Supplementation is recommended for all children with acute measles to reduce mortality and prevent blindness. * **Isolation:** Respiratory isolation is required; the virus is transmitted via droplet nuclei. * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia (secondary bacterial infection).

Q: Which is a common complication of mumps in children?

Aseptic meningitis. **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). While parotitis is the hallmark clinical feature, the virus is highly neurotropic, making involvement of the central nervous system (CNS) very common. **1. Why Aseptic Meningitis is correct:** Aseptic meningitis is the **most common extra-salivary complication** of mumps in children. It occurs in up to 10% of clinical cases, though CSF pleocytosis (increased white cells) is found in nearly 50% of patients even without meningeal symptoms. It is typically benign, characterized by headache, fever, and neck stiffness, and carries a much better prognosis than other viral meningitides. **2. Analysis of Incorrect Options:** * **B. Pancreatitis:** While a classic complication, it is less common than meningitis in the pediatric population. It presents with epigastric pain and elevated serum amylase (though amylase is also elevated in parotitis). * **C. Pneumonia:** This is not a standard complication of mumps. Respiratory involvement is more characteristic of Measles or RSV. * **D. Encephalitis:** Mumps encephalitis is a rare (1 in 6,000 cases) but severe complication. It involves parenchymal damage and carries a higher risk of permanent sequelae compared to the more common aseptic meningitis. **Clinical Pearls for NEET-PG:** * **Orchitis:** The most common complication in **post-pubertal males** (up to 30%), usually unilateral; rarely leads to absolute sterility. * **Oophoritis:** Occurs in ~7% of post-pubertal females. * **Deafness:** Mumps is a classic cause of sudden, usually unilateral, **sensorineural hearing loss**. * **Diagnosis:** Most commonly clinical; IgM ELISA is the gold standard for serology. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of MMR.

Q: What is the most common extracutaneous site of involvement in varicella infection?

Central Nervous System (CNS). **Explanation:** Varicella-Zoster Virus (VZV) is a highly neurotropic alpha-herpesvirus. While primary varicella (chickenpox) is characterized by a generalized pruritic vesicular rash, the **Central Nervous System (CNS)** is the most frequent site of extracutaneous involvement. The most common CNS manifestation in children is **acute cerebellar ataxia** (presenting with nystagmus and unsteady gait), whereas **encephalitis** is a more severe but rarer complication seen more frequently in adults. **Analysis of Options:** * **Central Nervous System (CNS) (Correct):** Due to the virus's inherent neurotropism, neurological complications (ataxia, encephalitis, or aseptic meningitis) occur more frequently than involvement of other organ systems. * **Lungs:** Varicella pneumonia is the most serious complication in adults and pregnant women, but it is statistically less common than CNS involvement across the general population. * **Liver:** While subclinical elevation of liver enzymes is common, clinically significant hepatitis is rare except in immunocompromised individuals. * **Heart:** Myocarditis is an extremely rare complication of VZV infection. **NEET-PG High-Yield Pearls:** * **Most common complication in children:** Secondary bacterial infection of skin lesions (usually *S. pyogenes* or *S. aureus*). * **Most common CNS complication in children:** Acute Cerebellar Ataxia (good prognosis). * **Most serious complication in adults:** Varicella Pneumonia. * **Tzanck Smear:** Shows multinucleated giant cells with Cowdry type A intranuclear inclusion bodies (common to VZV and HSV). * **Congenital Varicella Syndrome:** Characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis if infection occurs in the first 20 weeks of gestation.

Q: Which of the following is NOT a manifestation of congenital rubella?

Rash appears first on the trunk. **Explanation:** The correct answer is **A (Rash appears first on the trunk)** because in Rubella (German Measles), the characteristic maculopapular rash typically **begins on the face** and spreads cephalocaudally (downward) to the trunk and extremities. A rash starting on the trunk is more characteristic of Roseola Infantum (Exanthem Subitum). **Analysis of Options:** * **Pre-auricular lymphadenopathy (B):** This is a hallmark clinical feature of Rubella. Tender lymphadenopathy involving the **post-auricular, suboccipital, and posterior cervical nodes** often precedes the rash by 5–10 days. * **Arthralgia (C):** Joint pain and arthritis are common manifestations, especially in adolescent girls and adult women infected with Rubella. It usually involves the small joints of the hands. * **Retinopathy (D):** "Salt and pepper" retinopathy is the most common ocular manifestation of **Congenital Rubella Syndrome (CRS)**. While it usually does not affect vision, it is a critical diagnostic clue. **High-Yield Clinical Pearls for NEET-PG:** * **Gregg’s Triad (CRS):** 1. Cataracts (or glaucoma), 2. Sensorineural hearing loss (most common), 3. Congenital heart disease (Patent Ductus Arteriosus is most common; Peripheral Pulmonary Artery Stenosis is also seen). * **Forchheimer spots:** Small, red petechiae on the soft palate seen during the prodromal phase. * **Blueberry Muffin Rash:** Seen in neonates with CRS due to extramedullary hematopoiesis. * **Timing:** The risk of fetal malformation is highest (up to 85%) if the mother is infected during the **first trimester** (especially the first 8 weeks).

Q: A 10-month-old unimmunized child presents with fever and a diffuse maculopapular rash on day 4 of illness. The rash starts on the face and spreads downwards. The child also has postauricular lymphadenopathy. What is the most likely diagnosis?

Measles. **Explanation:** The clinical presentation of a high-grade fever followed by a **maculopapular rash on day 4** that spreads **cephalocaudally** (face downwards) in an **unimmunized** child is classic for **Measles (Rubeola)**. In Measles, the rash typically appears 3–4 days after the onset of prodromal symptoms (cough, coryza, conjunctivitis) and coincides with the peak of the fever. **Why the other options are incorrect:** * **Rubella (German Measles):** While Rubella also features a cephalocaudal rash and postauricular lymphadenopathy, the rash typically appears on **day 1** of illness, and the systemic symptoms (fever) are much milder than in Measles. * **Varicella (Chickenpox):** The rash is **pleomorphic** (macules, papules, and vesicles present simultaneously) and follows a **centripetal** distribution (trunk to extremities), unlike the downward spread in this case. * **Roseola Infantum (Exanthema Subitum):** Characteristically, the fever is very high for 3–5 days and **subsides abruptly** just as the rash appears ("fever falls, rash appears"). The rash starts on the trunk, not the face. **High-Yield Clinical Pearls for NEET-PG:** * **Koplik Spots:** Pathognomonic for Measles; seen on the buccal mucosa opposite the lower second molars during the prodromal stage. * **Vitamin A:** Supplementation is mandatory in Measles management to reduce morbidity and mortality (specifically preventing blindness and pneumonia). * **Complications:** The most common complication is **Otitis Media**; the most common cause of death is **Pneumonia**; the most delayed complication is **SSPE** (Subacute Sclerosing Panencephalitis). * **Infectivity:** Maximum during the prodromal stage (4 days before to 5 days after the appearance of the rash).

Q: What is the most common viral disease affecting the parotid glands?

Mumps. **Explanation:** The correct answer is **Mumps**. Mumps is an acute viral infection caused by the **Rubulavirus** (a Paramyxovirus). Its hallmark clinical feature is **nonsuppurative parotitis** (swelling of the parotid glands), which occurs in approximately 95% of symptomatic cases. The virus has a specific tropism for glandular and nervous tissue. **Why the other options are incorrect:** * **Measles (Rubeola):** Caused by a Morbillivirus, it primarily presents with the triad of cough, coryza, and conjunctivitis, followed by Koplik spots and a maculopapular rash. It does not typically involve the salivary glands. * **Rubella (German Measles):** Characterized by retroauricular and suboccipital lymphadenopathy and a 3-day rash. While it involves lymph nodes, it does not cause parotid swelling. * **Varicella (Chickenpox):** Caused by the Varicella-Zoster virus, it presents with a centripetal, pleomorphic rash ("dewdrop on a rose petal"). It does not target the parotid glands. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Respiratory droplets; most infectious 48 hours before the onset of parotitis. * **Complications:** * **Orchitis:** Most common complication in post-pubertal males (usually unilateral; rarely leads to sterility). * **Aseptic Meningitis:** Most common neurological complication. * **Pancreatitis:** A classic association to remember for exams. * **Oophoritis:** Seen in 5% of post-pubertal females. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain is most common) administered as part of the MMR vaccine.

Q: A previously healthy child develops bacterial meningitis. Assuming no specific contraindications, which of the following is the drug of choice?

Ceftriaxone. **Explanation:** The primary goal in treating bacterial meningitis is the rapid administration of bactericidal antibiotics that achieve high concentrations in the cerebrospinal fluid (CSF). **Why Ceftriaxone is the Correct Answer:** Ceftriaxone (a 3rd-generation cephalosporin) is the drug of choice for empirical treatment of bacterial meningitis in children. It covers the most common pathogens—*Streptococcus pneumoniae* and *Neisseria meningitidis*. Its advantages include excellent CSF penetration, a long half-life (allowing once or twice daily dosing), and high efficacy against penicillin-resistant strains of *S. pneumoniae*. **Why the Other Options are Incorrect:** * **Erythromycin:** This is a macrolide that is primarily bacteriostatic and has very poor penetration into the blood-brain barrier (BBB), making it ineffective for CNS infections. * **Penicillin V:** This is an oral penicillin with low bioavailability and poor CSF penetration; it is never used for meningitis. * **Penicillin G:** While historically used for meningococcal meningitis, increasing resistance in *S. pneumoniae* and the requirement for very frequent dosing make it a second-line agent compared to Ceftriaxone. **High-Yield Clinical Pearls for NEET-PG:** * **Empirical Therapy:** In children >1 month, the standard regimen is **Ceftriaxone + Vancomycin** (to cover highly resistant *S. pneumoniae*). * **Neonatal Meningitis (<1 month):** The common organisms are *GBS, E. coli,* and *Listeria*. The drug of choice is **Ampicillin + Cefotaxime** (or Gentamicin). * **Avoid Ceftriaxone in Neonates:** It can displace bilirubin from albumin, increasing the risk of **kernicterus**, and can precipitate with intravenous calcium. * **Steroids:** Dexamethasone should be given *before* or with the first dose of antibiotics to reduce the risk of hearing loss, especially in *H. influenzae* type b meningitis.

Question 1

An 8-month-old girl presented with sudden onset of high fever (103	extdegree F). Despite the absence of signs of upper respiratory tract infection, meningitis, or encephalitis, her fever escalated to 105	extdegree F, leading to a febrile seizure. Upon examination by the pediatrician, the child's temperature had subsided, and a generalized papular rash was noted. What is the most likely diagnosis?

Accepted Answer

Roseola infantum caused by human herpes virus 6

Answer

Erythema infectiosum caused by parvovirus B19

Answer

Hand-foot-and-mouth disease caused by Coxsackievirus A

Answer

Measles caused by Morbillivirus

Question 2

What is the most fatal complication of measles?

Accepted Answer

Subacute sclerosing panencephalitis (SSPE)

Answer

Pneumonia

Answer

Polyps

Answer

Otitis media

Question 3

An 8-year-old boy presented with a 4-day history of swelling on both sides of the face, below the ears. The swelling first started on the left side and then appeared on the right side 3 days later. What is the most likely diagnosis?

Accepted Answer

Epidemic parotitis

Answer

Bacterial sialadenitis

Answer

Sialadenosis

Answer

Sialadenitis

Question 4

All of the following statements regarding measles are true except?

Accepted Answer

Rash appears first on the leg

Answer

Koplik spots are seen on the buccal mucosa

Answer

Long-term complications may be seen in the form of Subacute Sclerosing Panencephalitis (SSPE)

Answer

Caused by an RNA virus

Question 5

Which is a common complication of mumps in children?

Accepted Answer

Aseptic meningitis

Answer

Pancreatitis

Answer

Pneumonia

Answer

Encephalitis

Question 6

What is the most common extracutaneous site of involvement in varicella infection?

Accepted Answer

Central Nervous System (CNS)

Answer

Heart

Answer

Lungs

Answer

Liver

Question 7

Which of the following is NOT a manifestation of congenital rubella?

Accepted Answer

Rash appears first on the trunk

Answer

Pre-auricular lymphadenopathy

Answer

Arthralgia

Answer

Retinopathy

Question 8

A 10-month-old unimmunized child presents with fever and a diffuse maculopapular rash on day 4 of illness. The rash starts on the face and spreads downwards. The child also has postauricular lymphadenopathy. What is the most likely diagnosis?

Accepted Answer

Measles

Answer

Rubella

Answer

Varicella

Answer

Roseola infantum

Question 9

What is the most common viral disease affecting the parotid glands?

Accepted Answer

Mumps

Answer

Measles

Answer

Rubella

Answer

Varicella

Question 10

A previously healthy child develops bacterial meningitis. Assuming no specific contraindications, which of the following is the drug of choice?

Accepted Answer

Ceftriaxone

Answer

Erythromycin

Answer

Penicillin V

Answer

Penicillin G

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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