Infectious Diseases Practice Questions

Q: Which is the most common complication of this rash?

Secondary skin infections. ***Secondary skin infections*** - **Intensely pruritic chickenpox vesicles** provoke scratching, disrupting the skin barrier and allowing bacterial superinfection by organisms such as *Staphylococcus aureus* and *Streptococcus pyogenes*. - **Secondary skin infection** is the most frequent complication of pediatric varicella, occurring more often than respiratory or ear complications. *Otitis media* - **Otitis media** can complicate varicella, but it is less common than bacterial infection of scratched vesicles. - It is more typically associated with **respiratory viral infections**, rather than being the characteristic common complication of the varicella rash. *Reye syndrome* - **Reye syndrome** is associated with aspirin use during varicella or influenza infection, not directly with the rash itself. - It is now **extremely uncommon** in children because aspirin is generally avoided during viral illnesses. *Bronchopneumonia* - **Varicella pneumonia** is a serious but rare complication, occurring mainly in adults and immunocompromised patients rather than typical children. - Because **secondary skin infections** occur more frequently, bronchopneumonia is not the most common complication of pediatric varicella.

Q: Parotitis and orchitis are common manifestations of which disease?

Mumps. ***Mumps*** - **Mumps**, caused by a **Rubulavirus** in the Paramyxoviridae family, classically produces painful, often bilateral parotitis. - **Orchitis** is a recognized complication in post-pubertal males, making mumps the best match for both manifestations. *Rubella* - **Rubella** usually causes a mild maculopapular rash with **post-auricular and suboccipital lymphadenopathy**, rather than prominent parotid inflammation. - Although rubella is a viral exanthem, **parotitis and orchitis** are not its characteristic glandular and reproductive complications. *Diphtheria* - **Diphtheria** is caused by **Corynebacterium diphtheriae** and typically produces a pharyngeal gray pseudomembrane and cervical swelling. - Its characteristic toxin-mediated illness does not commonly cause **parotitis or orchitis**, so it does not fit the described combination. *Measles* - **Measles** is characterized by the **three Cs**—cough, coryza, and conjunctivitis—followed by a maculopapular rash and Koplik spots. - Common measles complications include **pneumonia and SSPE**, not the combination of parotitis and orchitis.

Q: Paralysis in polio is characterized by?

Lower motor neurone type. ***Lower motor neurone type*** - Poliovirus selectively destroys **anterior horn cells**, the motor neuron cell bodies in the spinal cord, producing a classic lower motor neuron pattern. - This causes **acute flaccid paralysis** with hypotonia, reduced or absent reflexes, and muscle wasting, typically affecting the limbs asymmetrically. *Symmetrical paralysis* - Poliomyelitis characteristically produces **asymmetrical paralysis**, because neuronal involvement is uneven and different limbs may be affected to different degrees. - Although weakness can involve multiple limbs, **symmetrical paralysis** is not the typical distribution and therefore does not best describe paralytic polio. *Exaggerated tendon reflexes* - **Exaggerated tendon reflexes** indicate an upper motor neuron lesion, which causes spasticity and hyperreflexia rather than the typical findings of polio. - Destruction of anterior horn cells produces a **lower motor neuron** syndrome, so reflexes are usually diminished or absent in affected muscles. *Tonic paralysis* - Poliomyelitis causes **flaccid paralysis** through anterior horn cell destruction, leading to loss of muscle tone rather than sustained contraction or rigidity. - **Tonic or spastic paralysis** is associated with upper motor neuron dysfunction or disorders such as tetanus, so it does not fit the characteristic polio presentation.

Q: Which of the following is NOT a contraindication to DPT vaccination?

Local reaction to a previous DPT dose. ***Local reaction to a previous DPT dose*** - A **local reaction**, such as redness, swelling, or pain at the injection site, is a common adverse effect rather than a contraindication to subsequent DPT doses. - Because these reactions do not predict serious adverse events, **vaccination should proceed** according to the recommended schedule. *High fever following a previous DPT dose* - **High fever** above 105°F (40.5°C) within 48 hours of a previous dose is a significant systemic reaction and a precaution for further pertussis vaccination. - This history may indicate increased susceptibility to **febrile seizures**; further pertussis-containing vaccination requires careful assessment rather than routine continuation. *Seizures after a previous DPT dose* - **Seizures** occurring within three days of a previous DPT dose are a major precaution because of concern for neurological adverse effects from the pertussis component. - In this situation, the **pertussis component** is generally avoided and diphtheria-tetanus (DT) vaccine may be used instead. *Infantile spasms* - **Infantile spasms** represent an unstable neurological disorder and are a contraindication or precaution to pertussis vaccination until the condition has been stabilized. - Deferring the pertussis component reduces concern about worsening **neurological complications** during an active or progressive seizure disorder.

Q: A 3-year-old child presents with symptoms of influenza. Aspirin is contraindicated in this patient due to the increased risk of which of the following conditions?

Reye's syndrome. ***Reye's syndrome*** - **Reye's syndrome** is associated with aspirin use during viral illnesses, especially influenza or varicella, in children. - It causes **acute encephalopathy** and hepatic microvesicular steatosis through mitochondrial dysfunction and impaired fatty-acid oxidation, often with hyperammonemia and cerebral edema. *Fanconi syndrome* - **Fanconi syndrome** is proximal renal tubular dysfunction causing abnormalities such as phosphate and bicarbonate wasting. - Although some drugs, including expired tetracycline and cisplatin, can cause it, **aspirin after influenza** is not a recognized typical trigger. *Thrombocytopenia* - Aspirin irreversibly inhibits **platelet aggregation** by blocking platelet cyclooxygenase and thromboxane production. - This may increase bleeding tendency, but it does not usually reduce the absolute platelet count to cause **thrombocytopenia**. *Gastric bleeding* - Aspirin can cause **gastric irritation and bleeding** through cyclooxygenase inhibition, making this a recognized adverse effect. - However, gastrointestinal bleeding is not the characteristic reason aspirin is avoided during childhood viral infections; the distinctive concern is **Reye's syndrome**.

Q: Absolute contraindications to pertussis vaccine include all of the following except?

Static neurological disease. ***Static neurological disease*** - **Static neurological disease** is not an absolute contraindication to pertussis vaccination because stable cerebral palsy, controlled seizures, or developmental delay does not generally worsen because of immunization. - Children with **stable neurological conditions** should receive pertussis-containing vaccines; the underlying, nonprogressive disorder does not by itself justify withholding protection against pertussis. *Progressive neurological disease* - **Progressive neurological disease** is considered a contraindication or reason to defer pertussis vaccination until the neurological condition is stabilized and evaluated. - Deferring vaccination helps avoid confusing **vaccine-related adverse effects** with ongoing disease progression and allows reassessment before further pertussis-containing doses. *Encephalopathy within seven days of previous dose* - **Encephalopathy within seven days** of a previous pertussis-containing vaccine dose, without another identifiable cause, is an absolute contraindication to additional pertussis vaccine. - Severe manifestations such as **altered consciousness, coma, or prolonged seizures** after the preceding dose indicate that further pertussis-containing doses should not be given. *Anaphylaxis after previous dose* - **Anaphylaxis after a previous dose** is an absolute contraindication because a subsequent exposure to the vaccine or a shared component may cause another life-threatening reaction. - A history of **severe immediate allergic reaction** to the vaccine or one of its components requires avoiding further doses and considering an appropriate alternative immunization strategy.

Q: What is the characteristic feature of early congenital syphilis?

Vesicular rash with bulla over palms and soles. ***Vesicular rash with bulla over palms and soles*** - A **vesiculobullous rash** involving the palms and soles is characteristic of early congenital syphilis and is termed syphilitic pemphigus. - The bullae contain a high burden of **Treponema pallidum**, making these lesions highly infectious; other early findings include snuffles, hepatosplenomegaly, and osteochondritis. *Saddle nose* - **Saddle nose** is a late manifestation of congenital syphilis, resulting from destructive inflammation and damage to the nasal cartilage rather than early infection. - Early congenital syphilis more typically causes **snuffles**, hepatosplenomegaly, osteochondritis, and a vesiculobullous rash involving the palms and soles. *Interstitial keratitis with sabre skin* - **Interstitial keratitis** and sabre-like tibial changes are characteristic late manifestations of congenital syphilis, not the usual presentation before two years of age. - Interstitial keratitis forms part of **Hutchinson’s triad**, alongside sensorineural deafness and Hutchinson teeth, helping distinguish late from early disease. *Microcephaly* - **Microcephaly** is more classically associated with congenital infections such as cytomegalovirus and Zika virus, rather than being a hallmark of congenital syphilis. - The early syphilis pattern is dominated by **mucocutaneous lesions**, rhinitis, hepatosplenomegaly, and skeletal involvement rather than primary reduction in head size.

Q: What is the most common complication of rubella?

Polyarthritis. ***Polyarthritis*** - **Polyarthritis** is the most common complication of rubella, particularly in **adult females**, where it may occur in up to 70% of cases. - It commonly affects the **small joints, wrists, and knees**, probably through immune-complex mechanisms, and is usually self-limiting without permanent joint damage. *Orchitis* - **Orchitis** is not a typical rubella complication; it is classically associated with **mumps** infection. - Rubella more characteristically causes **arthralgia and polyarthritis**, especially in adult females, making orchitis a poor choice for the most common complication. *Encephalitis* - **Encephalitis** can occur after rubella but is a **rare neurological complication**, reported far less often than joint involvement. - The markedly greater frequency of **post-rubella polyarthritis** makes encephalitis unsuitable as the most common complication. *Thrombocytopenia* - **Thrombocytopenia** or post-infectious thrombocytopenic purpura may follow rubella but is **significantly rarer** than polyarthritis. - Because **joint symptoms** occur much more commonly, thrombocytopenia is not the best answer for the most common complication.

Q: A 2-month-old child born to an HIV-positive mother is under your care. Which of the following prophylactic therapies should be considered for this child?

Prophylaxis against Pneumocystis jiroveci pneumonia. ***Prophylaxis against Pneumocystis jiroveci pneumonia*** - **Pneumocystis jiroveci pneumonia** has peak incidence at **2–6 months** in HIV-infected infants and can rapidly cause severe respiratory failure. - **Cotrimoxazole (TMP-SMX)** prophylaxis is recommended from **4–6 weeks** for HIV-exposed infants until HIV infection is excluded or appropriate clinical and immunological recovery occurs. *Monthly evaluation for Kaposi sarcoma* - **Kaposi sarcoma** is rare in children and is not a common opportunistic infection requiring routine surveillance in HIV-exposed infants. - Routine monthly evaluation for Kaposi sarcoma is therefore not a standard **prophylactic therapy** or screening requirement. *Vitamin C supplementation* - Although adequate **nutrition** supports general health, vitamin C does not specifically prevent the major opportunistic infections associated with infant HIV exposure. - **Vitamin C supplementation** is therefore not the recommended targeted prophylaxis for preventing Pneumocystis jiroveci pneumonia. *Oral polio virus vaccine* - **Oral polio vaccine** is live attenuated, and live vaccines may be avoided in severely symptomatic or immunocompromised HIV-infected children. - **Cotrimoxazole prophylaxis** is the priority intervention for preventing Pneumocystis jiroveci pneumonia; where feasible, inactivated polio vaccine may be preferred.

Q: According to WHO staging, what stage is assigned to an HIV-infected child presenting with parotid enlargement?

Stage 2. ***Stage 2*** - **Persistent parotid enlargement** is classified as WHO **Clinical Stage 2** in children with HIV, indicating mild symptomatic disease beyond asymptomatic infection. - Stage 2 may also include **papular pruritic eruptions**, extensive warts, persistent hepatosplenomegaly, and recurrent upper respiratory tract infections such as sinusitis or otitis media. *Stage 4* - **Stage 4** represents severe, AIDS-defining illness, such as Pneumocystis pneumonia, esophageal candidiasis, or HIV wasting syndrome. - Isolated **parotid enlargement** is a mild symptomatic manifestation and lacks the severe opportunistic infection or wasting features required for Stage 4. *Stage 1* - **Stage 1** is primarily asymptomatic infection; the characteristic permitted finding is persistent generalized lymphadenopathy. - Parotid enlargement is a **symptomatic progression** beyond Stage 1 and is therefore assigned to Clinical Stage 2. *Stage 3* - **Stage 3** includes advanced manifestations such as moderate malnutrition, persistent diarrhea, oral candidiasis, or pulmonary tuberculosis. - Although **lymphocytic interstitial pneumonitis** is associated with Stage 3, isolated persistent parotid enlargement itself is classified as Stage 2.

Question 1

Which is the most common complication of this rash?

Accepted Answer

Secondary skin infections

Answer

Otitis media

Answer

Bronchopneumonia

Answer

Reye syndrome

Question 2

Parotitis and orchitis are common manifestations of which disease?

Accepted Answer

Mumps

Answer

Diphtheria

Answer

Measles

Answer

Rubella

Question 3

Paralysis in polio is characterized by?

Accepted Answer

Lower motor neurone type

Answer

Exaggerated tendon reflexes

Answer

Symmetrical paralysis

Answer

Tonic paralysis

Question 4

Which of the following is NOT a contraindication to DPT vaccination?

Accepted Answer

Local reaction to a previous DPT dose

Answer

High fever following a previous DPT dose

Answer

Infantile spasms

Answer

Seizures after a previous DPT dose

Question 5

A 3-year-old child presents with symptoms of influenza. Aspirin is contraindicated in this patient due to the increased risk of which of the following conditions?

Accepted Answer

Reye's syndrome

Answer

Gastric bleeding

Answer

Thrombocytopenia

Answer

Fanconi syndrome

Question 6

Absolute contraindications to pertussis vaccine include all of the following except?

Accepted Answer

Static neurological disease

Answer

Progressive neurological disease

Answer

Anaphylaxis after previous dose

Answer

Encephalopathy within seven days of previous dose

Question 7

What is the characteristic feature of early congenital syphilis?

Accepted Answer

Vesicular rash with bulla over palms and soles

Answer

Microcephaly

Answer

Saddle nose

Answer

Interstitial keratitis with sabre skin

Question 8

What is the most common complication of rubella?

Accepted Answer

Polyarthritis

Answer

Encephalitis

Answer

Orchitis

Answer

Thrombocytopenia

Question 9

A 2-month-old child born to an HIV-positive mother is under your care. Which of the following prophylactic therapies should be considered for this child?

Accepted Answer

Prophylaxis against Pneumocystis jiroveci pneumonia

Answer

Monthly evaluation for Kaposi sarcoma

Answer

Vitamin C supplementation

Answer

Oral polio virus vaccine

Question 10

According to WHO staging, what stage is assigned to an HIV-infected child presenting with parotid enlargement?

Accepted Answer

Stage 2

Answer

Stage 1

Answer

Stage 3

Answer

Stage 4

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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