Infectious Diseases Practice Questions

Q: An infant has fever, one episode of febrile convulsions, and is admitted for observation. The fever then subsided and was followed by a rash on the abdomen and chest, which is maculopapular and erythematous. What is the cause?

Roseola infantum (Sixth disease). ***Roseola infantum (Sixth disease)*** - Characterized by **high fever** (often a trigger for **febrile seizures**) followed by an **erythematous, maculopapular rash** that appears as the fever subsides. - This clinical presentation is highly suggestive of **Roseola infantum**, caused by **Human Herpesvirus 6 (HHV-6)** or sometimes **HHV-7**, primarily affecting infants and young children. *Measles (Rubeola)* - Measles rash typically presents as a **maculopapular rash** that starts on the **face** and spreads downwards, appearing **during the fever**'s peak, not after it subsides. - Classic symptoms also include **Koplik spots** (small white spots inside the mouth) and the **three Cs: cough, coryza, and conjunctivitis**, which are not mentioned. *Typhoid fever (Salmonella Typhi infection)* - Typhoid fever is characterized by a **prolonged high fever**, **bradycardia**, and typically a **rose spot rash** (small, faint, salmon-colored macules) primarily on the trunk, appearing later in the illness. - Febrile convulsions are less common, and the timing and nature of the rash do not match the description provided. *Dengue fever (DENV infection)* - Dengue fever presents with **high fever**, severe headache, retro-orbital pain, muscle and joint pains (breakbone fever), and often a **maculopapular or petechial rash** that can appear around the time the fever starts to drop, but usually accompanies other severe symptoms. - While a rash can occur, the distinct pattern of fever followed by a rash as the fever resolves, with febrile convulsions without other characteristic dengue symptoms, makes it less likely.

Q: Which of the following statements about rashes in children is incorrect?

Varicella - typically appears on day 1. ***Varicella - typically appears on day 1*** - This statement is incorrect because the typical rash of **varicella** (**chickenpox**) usually appears on **day 2 or 3** of the illness, following a prodrome of fever and malaise. - The rash begins as macules, quickly progressing to papules, vesicles, and then crusts, often in a **centrifugal distribution**. *Typhus - typically appears on day 5* - This statement is correct. The rash of **epidemic typhus** (caused by *Rickettsia prowazekii*) typically appears around **day 5 or 6** following the onset of fever. - It usually starts on the trunk and spreads peripherally, often sparing the face, palms, and soles. *Typhoid - typically appears on day 5* - This statement is correct. The classic "rose spots" rash of **typhoid fever** (caused by *Salmonella Typhi*) typically appears around **day 5 to 7** of the illness. - These are faint, salmon-colored, blanching maculopapular lesions, usually found on the trunk and chest. *Measles - typically appears on day 4* - This statement is correct. The characteristic **maculopapular rash of measles** (rubeola) typically appears around **day 3 or 4** after the onset of the prodromal symptoms (fever, cough, coryza, conjunctivitis). - The rash starts on the face and behind the ears, then spreads cephalocaudally over the body.

Q: What is the appropriate management for a child who has been bitten by a cat?

All of the options are true. ***All of the options are true*** - Comprehensive management of a cat bite requires **multiple interventions** addressing infection prevention, rabies prophylaxis, and immediate wound care. - Cat bites have a high infection rate (30-50%) due to deep puncture wounds from sharp teeth that inoculate bacteria like *Pasteurella multocida*, *Streptococcus*, and *Staphylococcus* deep into tissues. *Administer prophylactic antibiotics to prevent infection* - **Prophylactic antibiotics** are recommended for cat bites due to the high risk of infection (particularly *Pasteurella multocida*). - First-line therapy is typically **amoxicillin-clavulanate** (Augmentin), which covers the most common pathogens. - Deep puncture wounds, bites to hands/feet, immunocompromised patients, and delayed presentation warrant antibiotic prophylaxis. *Rabies vaccination may be necessary* - **Rabies post-exposure prophylaxis (PEP)** is crucial if the cat is unvaccinated, a stray, or its vaccination status is unknown. - Rabies is nearly 100% fatal once symptoms appear, making prophylaxis essential in high-risk situations. - The decision depends on local rabies prevalence and assessment of the animal's behavior and health status. *Thoroughly clean the wound* - **Immediate and copious irrigation** with soap and water or saline is the most important initial step in management. - This reduces bacterial load significantly and decreases infection risk. - Most cat bite wounds should be left open (not sutured) due to high infection risk, unless on the face for cosmetic reasons.

Q: Which of the following statements about Koplik spots is true?

All of the options.. All of the options. - Koplik spots are pathognomonic of measles, meaning their presence is a definitive indicator of the disease [1]. - They typically appear as tiny, white spots on an erythematous base on the buccal mucosa, often opposite the molars [1]. Pathognomonic of measles. - While Koplik spots are a hallmark sign of measles, stating this is true alone doesn't encompass all true aspects for this question [1]. - Their presence, however, is a strong diagnostic indicator of rubeola. Present on buccal mucosa opposite the molars. - This is a correct description of their typical location, but not a complete answer to the question "Which of the following statements about Koplik spots is true?" if other options also hold true [1]. - These spots are found on the mucous membrane lining the inside of the cheeks [1]. Not always present. - Koplik spots are transient and may not be present throughout the entire course of measles, particularly if a patient is seen later in the disease [1]. - They also can be missed if not specifically looked for or if they are very few in number.

Q: Which of the following is the most characteristic feature of the rash distribution in chickenpox?

More concentrated on the trunk than limbs. ***More concentrated on the trunk than limbs*** - The rash of chickenpox (varicella) has a **pathognomonic centripetal distribution**, meaning it is most dense on the **trunk, face, and scalp**, with fewer lesions on the extremities. - This characteristic distribution pattern is the **most distinguishing feature** of chickenpox and helps differentiate it from other vesicular exanthems. - References: Nelson Textbook of Pediatrics, Ghai Essential Pediatrics *Superficial and not deep-seated* - While chickenpox lesions are indeed **superficial vesicles** affecting the epidermis, this characteristic is less specific. - Many other viral exanthems also produce superficial lesions, making this a less distinguishing feature. *Affects palms and soles* - **Incorrect.** Chickenpox lesions characteristically **spare the palms and soles**. - Involvement of palms and soles suggests hand, foot, and mouth disease, secondary syphilis, or other conditions. *Evolves rapidly with new spots appearing in waves over days* - While true that chickenpox lesions appear in **crops over 3-5 days** creating the "**dewdrops on a rose petal**" appearance with lesions in various stages, this describes the **temporal evolution** rather than the **spatial distribution pattern**. - The question specifically asks about the most characteristic feature, and centripetal distribution is more pathognomonic than the cropping pattern.

Q: In which of the following conditions can strawberry tongue be observed?

Both conditions mentioned above. ***Both conditions mentioned above*** - **Strawberry tongue** is a characteristic finding in both **streptococcal scarlet fever** and **Kawasaki disease** [2]. - In both conditions, the tongue initially appears white with prominent red papillae, resembling a white strawberry, and later becomes bright red, described as a red strawberry [2]. *Streptococcal scarlet fever* - **Strawberry tongue** is a classic symptom of **scarlet fever**, which is caused by Group A Streptococcus infection [2]. - Other symptoms often include a **diffuse red rash**, sore throat, and fever [2]. *Kawasaki disease* - **Strawberry tongue** is one of the mucocutaneous manifestations of **Kawasaki disease**, a multisystem vasculitis primarily affecting young children [1]. - Other key features include **fever lasting ≥5 days**, conjunctival injection, rash, cervical lymphadenopathy, and extremity changes [1]. *None of the options* - This option is incorrect because **strawberry tongue** is indeed observed in both scarlet fever and Kawasaki disease [1], [2]. - The presence of this specific tongue appearance is a well-documented clinical sign in these two distinct conditions.

Q: A 3-month-old baby presents with deafness, cataract, and patent ductus arteriosus. Which of the following is the most likely diagnosis?

Congenital rubella syndrome. ***Congenital rubella syndrome*** - The classic triad of **deafness**, **cataracts**, and **patent ductus arteriosus (PDA)** is highly characteristic of congenital rubella syndrome. - This syndrome results from **maternal rubella infection** during the first trimester of pregnancy. *Congenital herpes simplex virus infection* - Typically presents with **skin vesicles**, **keratoconjunctivitis**, and **encephalitis**. - **Deafness, cataracts, and PDA** are not common features of congenital HSV. *Congenital toxoplasmosis* - The classic triad involves **chorioretinitis**, **hydrocephalus**, and **intracranial calcifications**. - While it can cause microcephaly and seizures, **deafness, cataracts, and PDA** are not hallmark features. *Congenital cytomegalovirus infection* - Often causes **sensorineural hearing loss** and sometimes **chorioretinitis**, but the combination with **cataracts** and **PDA** is atypical. - Other common features include **periventricular calcifications**, **hepatosplenomegaly**, and **thrombocytopenia**.

Q: What is the most serious complication of measles?

Pneumonia. ***Pneumonia*** - **Pneumonia**, particularly **giant cell pneumonia**, is the most common cause of **measles-related deaths** in young children. - It results from the **direct viral infection** of the lungs or a **secondary bacterial superinfection**. *Croup* - **Croup (laryngotracheobronchitis)** can be a complication of measles, but it is typically **less severe** and **less life-threatening** than pneumonia. - It primarily affects the **upper airways**, causing a barking cough and stridor. *Meningo-encephalitis* - **Meningo-encephalitis** is a serious, albeit **less common**, complication of measles, occurring in approximately 1 in 1,000 cases. - While potentially fatal or leading to neurological sequelae, it is **outranked by pneumonia** in terms of overall mortality attributed to measles. *Otitis media* - **Otitis media** (middle ear infection) is a common complication of measles, but it is generally **not life-threatening**. - It usually responds well to **antibiotic treatment** and rarely leads to severe outcomes.

Q: Which of the following statements regarding Pertussis is INCORRECT?

Cerebellar ataxia is a known complication.. ***Cerebellar ataxia is a known complication.*** - **Cerebellar ataxia** is not a typical or known complication of pertussis. Complications usually involve the respiratory, neurological (e.g., seizures, encephalopathy due to hypoxia), and nutritional systems due to severe coughing. - While neurological complications can occur, **ataxia** specifically is not frequently sighted in the context of pertussis. *Some infections may be subclinical.* - Some individuals, especially those partially immunized or older, can experience **subclinical or atypical infections** with pertussis, often presenting as a mild cough. - This characteristic makes it difficult to control the spread of the disease as infected individuals may not be recognized. *The most infective stage is the catarrhal stage.* - The **catarrhal stage**, characterized by non-specific cold-like symptoms, is the most contagious phase because bacterial shedding is highest. - During this stage, symptoms are mild and often indistinguishable from a common cold, leading to widespread transmission before diagnosis. *The drug of choice is Erythromycin.* - **Erythromycin**, or other macrolides like azithromycin or clarithromycin, are the drugs of choice for treating pertussis. - These antibiotics are most effective when administered early in the **catarrhal stage** to reduce disease severity and prevent transmission.

Q: A baby from a second degree consanguineous marriage presents with diarrhoea and redness in the perianal diaper area. What is the most likely diagnosis?

Fungal infection. ***Fungal infection (Candida diaper dermatitis)*** - **Diarrhea with perianal diaper rash** is the classic presentation of **Candida (fungal) diaper dermatitis**, the most common cause of diaper rash in infants with diarrhea. - **Diarrhea increases skin moisture and alters pH**, creating optimal conditions for **Candida albicans overgrowth**. - **Perianal involvement with bright erythema** is characteristic of Candida, often with **satellite lesions** and involvement of skin folds. - This is a **clinical diagnosis** based on distribution pattern and association with diarrhea; consanguinity is not directly relevant to this common condition. *Lactose intolerance* - **Congenital lactase deficiency** is extremely rare (< 50 cases worldwide) and unlikely to be the primary diagnosis. - While **secondary lactose intolerance** can occur with gastroenteritis causing diarrhea, it doesn't explain the **specific perianal rash pattern** described. - The perianal redness in lactose malabsorption would be **irritant contact dermatitis** from acidic stools, which would secondarily get infected with **Candida** - making fungal infection the more complete diagnosis. *Shigella infection* - Typically presents with **bloody diarrhea (dysentery)**, high fever, abdominal cramps, and tenesmus. - Would not specifically cause the **perianal diaper rash pattern** characteristic of Candida. - Consanguinity doesn't predispose to this bacterial infection. *Salmonella infection* - Usually presents with **fever, vomiting, and systemic symptoms** along with diarrhea. - May cause bloody or non-bloody diarrhea but doesn't explain the **characteristic perianal redness pattern**. - Not associated with consanguinity as it's an acquired infectious disease.

Question 1

An infant has fever, one episode of febrile convulsions, and is admitted for observation. The fever then subsided and was followed by a rash on the abdomen and chest, which is maculopapular and erythematous. What is the cause?

Accepted Answer

Roseola infantum (Sixth disease)

Answer

Measles (Rubeola)

Answer

Typhoid fever (Salmonella Typhi infection)

Answer

Dengue fever (DENV infection)

Question 2

Which of the following statements about rashes in children is incorrect?

Accepted Answer

Varicella - typically appears on day 1

Answer

Typhoid - typically appears on day 5

Answer

Typhus - typically appears on day 5

Answer

Measles - typically appears on day 4

Question 3

What is the appropriate management for a child who has been bitten by a cat?

Accepted Answer

All of the options are true

Answer

Administer prophylactic antibiotics to prevent infection

Answer

Rabies vaccination may be necessary

Answer

Thoroughly clean the wound

Question 4

Which of the following statements about Koplik spots is true?

Accepted Answer

All of the options.

Answer

Pathognomonic of measles.

Answer

Present on buccal mucosa opposite the molars.

Answer

Not always present.

Question 5

Which of the following is the most characteristic feature of the rash distribution in chickenpox?

Accepted Answer

More concentrated on the trunk than limbs

Answer

Superficial and not deep-seated

Answer

Affects palms and soles

Answer

Evolves rapidly with new spots appearing in waves over days.

Question 6

In which of the following conditions can strawberry tongue be observed?

Accepted Answer

Both conditions mentioned above

Answer

Streptococcal scarlet fever

Answer

Kawasaki disease

Answer

None of the options

Question 7

A 3-month-old baby presents with deafness, cataract, and patent ductus arteriosus. Which of the following is the most likely diagnosis?

Accepted Answer

Congenital rubella syndrome

Answer

Congenital herpes simplex virus infection

Answer

Congenital toxoplasmosis

Answer

Congenital cytomegalovirus infection

Question 8

What is the most serious complication of measles?

Accepted Answer

Pneumonia

Answer

Croup

Answer

Otitis media

Answer

Meningo-encephalitis

Question 9

Which of the following statements regarding Pertussis is INCORRECT?

Accepted Answer

Cerebellar ataxia is a known complication.

Answer

The drug of choice is Erythromycin.

Answer

Some infections may be subclinical.

Answer

The most infective stage is the catarrhal stage.

Question 10

A baby from a second degree consanguineous marriage presents with diarrhoea and redness in the perianal diaper area. What is the most likely diagnosis?

Accepted Answer

Fungal infection

Answer

Shigella infection

Answer

Salmonella infection

Answer

Lactose intolerance

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?