Highly contagious paramyxovirus with prodromal cough/coryza/conjunctivitis and Koplik spots, followed by cephalocaudal maculopapular rash; vaccine-preventable.
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Risk factors
- Unimmunized status
- International travel to endemic areas
- Vitamin A deficiency
- Immunocompromise
- Crowded living conditions
- Infants 6-12 months between waning maternal antibody and first MMR dose
Pathophysiology
Virus enters via respiratory epithelium, replicates in regional lymph nodes, and undergoes viremia with seeding of skin, mucosae, and reticuloendothelial system. Immune-mediated cytotoxicity produces rash and Koplik spots. Profound transient immunosuppression follows infection ('immune amnesia'), increasing susceptibility to other infections for months.
Clinical presentation
Symptoms
- Prodrome (3-5 days): high fever (often 40 °C), cough, coryza, conjunctivitis (the three Cs), malaise
- Koplik spots: 1-2 mm bluish-white papules on a red base on buccal mucosa opposite molars, 1-2 days before rash
- Rash: erythematous maculopapular eruption beginning on face/hairline, spreading cephalocaudally over 3 days, becoming confluent and brownish before fading
Signs / physical exam
- Conjunctival injection without purulent discharge
- Cervical lymphadenopathy
- Rash blanches early then darkens with desquamation
Classic findings
Three Cs + Koplik spots + cephalocaudal rash in an unvaccinated child.
Differential diagnosis
- Rubella — Milder prodrome, posterior auricular and suboccipital adenopathy, pinker faster-spreading rash
- Roseola (HHV-6) — High fever then rash that appears AS fever defervesces; younger child
- Erythema infectiosum (parvovirus B19) — 'Slapped cheek' rash without prodrome; lacy reticular extension on extremities
- Scarlet fever — Sandpaper rash, strawberry tongue, sore throat with strep, no conjunctivitis or Koplik spots
- Kawasaki disease — ≥5 days fever + conjunctivitis + mucosal changes + extremity changes + rash + lymphadenopathy
- Drug eruption / DRESS — Recent new medication; eosinophilia and facial edema
- Enteroviral exanthem — Summer/fall, hand-foot-mouth pattern with vesicles
Diagnostic workup
Diagnostic criteria
Clinical case definition (fever, generalized maculopapular rash ≥3 days, plus cough/coryza/conjunctivitis) confirmed by IgM positive or RT-PCR positive.
Labs
- Measles-specific IgM and IgG (acute and convalescent)
- RT-PCR on nasopharyngeal swab, throat swab, urine, or blood — most sensitive within the first 5 days
- Report immediately to public health (CDC nationally notifiable)
- CBC: leukopenia and lymphopenia
Imaging
- Chest x-ray if pneumonia suspected
Treatment
First-line
- Supportive care: antipyretics, hydration, isolation (airborne precautions for 4 days after rash onset)
- Vitamin A: 200,000 IU PO on days 1 and 2 (50,000 IU if <6 months, 100,000 IU if 6-11 months) — WHO/AAP recommend for all children with measles; reduces mortality and ocular complications
- Post-exposure prophylaxis: MMR vaccine within 72 hours OR immunoglobulin within 6 days for high-risk contacts (infants <6 months, pregnant women, immunocompromised)
Routine prevention (ACIP)
- MMR vaccine — first dose 12-15 months, second dose 4-6 years
- MMR is a live attenuated vaccine; contraindicated in pregnancy and severe immunocompromise
Outbreak / accelerated schedule
- Infants 6-11 months traveling internationally: one early MMR dose (does not count toward routine series)
- Catch-up: two MMR doses ≥28 days apart
Second-line / adjunct
- Ribavirin has been used anecdotally for severe disease but is not standard
- Treat bacterial superinfections (otitis, pneumonia)
Complications
- Otitis media (most common)
- Pneumonia (most common cause of death; primary measles giant-cell pneumonia or secondary bacterial)
- Acute disseminated encephalomyelitis (ADEM) — 1 per 1,000
- Subacute sclerosing panencephalitis (SSPE) — fatal, years after infection, more common with infection <2 yr
- Diarrhea and dehydration
- Immune amnesia — increased risk of other infections for months
- Corneal ulceration and blindness in vitamin A-deficient children
PANCE pearls
- Koplik spots appear before the rash and are pathognomonic.
- Vitamin A for every child with measles regardless of nutritional status — a cheap, high-yield intervention.
- Two doses of MMR are 97% effective; outbreaks reflect undervaccination, not vaccine failure.
- MMR is a live vaccine — contraindicated in pregnancy and severe immunocompromise; counsel postpartum women.
- Measles induces months-long immune amnesia, increasing risk of other infections after recovery.
References
- ACIP — CDC/ACIP Recommendations for Prevention of Measles, Rubella, Congenital Rubella Syndrome, and Mumps (McLean et al., MMWR Recomm Rep 2013;62(RR-04))
- AAP Red Book — American Academy of Pediatrics Red Book — Measles chapter
- WHO — WHO Measles Vaccines: Position Paper
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