Infectious Disease · Viral Exanthems
The facts most likely to be tested
The prodrome of measles is characterized by the three Cs: cough, coryza, and conjunctivitis.
Koplik spots, which are pathognomonic small white or bluish-gray lesions on the buccal mucosa, appear 1–2 days before the onset of the rash.
The maculopapular rash typically begins on the face and spreads cephalocaudally (head to toe) to involve the palms and soles.
Measles is caused by the Paramyxovirus and is transmitted via respiratory droplets with a high secondary attack rate.
Vitamin A supplementation is the standard of care to reduce morbidity and mortality in all children diagnosed with measles.
Pneumonia is the most common cause of measles-related mortality in children.
Subacute sclerosing panencephalitis (SSPE) is a rare, fatal, delayed complication occurring years after the initial infection due to persistent viral replication.
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A 4-year-old unvaccinated boy is brought to the clinic with a 4-day history of high fever, barking cough, runny nose, and red, watery eyes. Physical examination reveals small, white, salt-like lesions on the inner cheeks opposite the molars. A blanching, erythematous maculopapular rash is noted starting at the hairline and spreading downward to the trunk.
What is the most appropriate intervention to reduce the risk of severe complications in this patient?
Vitamin A supplementation
The patient presents with the classic triad of the three Cs and pathognomonic Koplik spots, confirming measles; Vitamin A is indicated for all pediatric patients with measles to decrease morbidity and mortality.
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Etiology / Epidemiology
Highly contagious paramyxovirus transmitted via respiratory droplets; primarily affects unvaccinated children.
Clinical Manifestations
Prodrome of cough, coryza, conjunctivitis followed by Koplik spots and a cephalocaudal rash.
Diagnosis
Clinical diagnosis; confirm with measles IgM antibody or RT-PCR of throat/nasopharyngeal swabs.
Treatment
Supportive care; Vitamin A supplementation is the only intervention shown to reduce mortality.
Prognosis
Most recover fully; pneumonia is the most common cause of death; monitor for subacute sclerosing panencephalitis.
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Epidemiology & Etiology
Caused by the measles virus, a single-stranded RNA virus. It remains one of the most infectious diseases, with a secondary attack rate of up to 90% in susceptible household contacts. Incidence is highest in regions with low MMR vaccine coverage.
Pertinent Anatomy
The virus enters via the respiratory mucosa and conjunctiva. Systemic spread occurs via the lymphatic system to the reticuloendothelial system, leading to widespread epithelial involvement.
Pathophysiology
The virus replicates in the respiratory epithelium before causing viremia. The characteristic rash is a result of T-cell mediated immune response against infected endothelial cells in the skin. This immune activation explains the transient immunosuppression that follows infection.
Clinical Manifestations
The prodrome features the classic triad of cough, coryza, and conjunctivitis. Koplik spots (small white lesions on the buccal mucosa) appear 24-48 hours before the maculopapular rash, which spreads from the face downward. Respiratory distress or encephalitis are critical red flags requiring immediate hospitalization.
Diagnosis
Diagnosis is primarily clinical in the setting of known exposure. RT-PCR is the preferred laboratory test for confirmation. Serology for measles IgM is also diagnostic, though it may be falsely negative in the first 72 hours of rash onset.
Treatment
Management is primarily supportive with fluids and antipyretics. Vitamin A (200,000 IU daily for 2 days) is mandatory to reduce morbidity and mortality. Live vaccines are contraindicated in pregnancy and severe immunocompromise.
Prognosis
While most cases are self-limiting, pneumonia is the leading cause of measles-related mortality. Long-term, rare complications include subacute sclerosing panencephalitis (SSPE), which occurs years after the initial infection.
Differential Diagnosis
Rubella: milder prodrome, postauricular lymphadenopathy
Roseola: high fever followed by rash after defervescence
Erythema infectiosum: 'slapped cheek' appearance
Scarlet fever: sandpaper texture rash, strawberry tongue
Kawasaki disease: prolonged fever >5 days, mucocutaneous lymph node syndrome