Measles
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Direct answer
Koplik spots — bluish-white grains of salt on an erythematous base on the buccal mucosa opposite the lower molars — seal the diagnosis of measles on day two or three of a feverish illness with cough, coryza and conjunctivitis, the three Cs. The rash appears around day four, starting behind the ears and hairline, sweeping down over face, trunk and limbs as a blanching maculopapular eruption that later desquamates, and the child is infectious from four days before to four days after its onset. Management is supportive with vitamin A in age-dosed repeats, and the complications — pneumonia, diarrhoea, keratomalacia, encephalitis and the delayed SSPE — are what exam and ward both worry about.
What you must remember
- The paramyxovirus (Morbillivirus) spreads by droplet and airborne routes with near-universal susceptibility; infectivity runs from four days before to four days after the rash, highest in the catarrhal stage.
- Prodrome: stepwise rising fever with the three Cs for three to four days before any rash; Koplik spots appear on about day two and have usually vanished by the time the rash erupts.
- The rash: maculopapular, blanching early, blotchy and confluent later; hairline and postauricular start, downward spread, lasting about six days, ending with fine desquamation.
- Vitamin A: two doses 24 hours apart — 50,000 units below six months, 100,000 at 6–11 months, 200,000 at 12 months and above — with a third dose after two to four weeks where deficiency or xerophthalmia is present; it reduces mortality.
- Pneumonia is the commonest cause of measles death, followed by diarrhoea; corneal ulceration and keratomalacia from acute vitamin A deficiency can blind within days.
- Post-measles encephalitis affects roughly one in a thousand in the days around the rash; subacute sclerosing panencephalitis appears years later with myoclonic jerks, deterioration and periodic EEG complexes — invariably fatal.
- Immunity after natural infection is lifelong; the Indian schedule gives MR-1 at nine completed months and MR-2 at 16–24 months.
- Post-exposure prophylaxis: vaccine within 72 hours for susceptible contacts; human normal immunoglobulin within six days for infants, pregnancy and the immunocompromised.
A typical exam case
A three-year-old unimmunised child of a migrant family: five days of rising fever, harsh cough, red watering eyes, and today a confluent rash over face and chest that began behind the ears; the mother recalls "white spots inside the cheeks" two days ago. He is toxic, photophobic, with early corneal haziness. The plan: isolate; vitamin A 200,000 units now and again tomorrow; corneal protection with antibiotic ointment and continued vitamin A; watch respiratory rate and hydration; treat superadded pneumonia if it appears. Feed the child — never "starve during rash" — and counsel that desquamation is expected. The examinable threads: the Koplik spots recalled from two days prior (already gone at rash), the infectivity window that dates which contacts need vaccine, the age-dosed vitamin A, and the eye as the organ to protect urgently. A teenager with myoclonus and measles at age two answers to a different name — SSPE — and the question becomes about the EEG.
Where students slip
The rash description is where marks bleed: the direction (hairline and behind ears, downward and outward) and its appearance as the fever begins to fall, not rise, are the tested details. The second slip is vitamin A dosing by age — the three-tier schedule is forgotten and "one dose" is written. Third, Koplik timing: they are a prodrome sign, usually gone by the rash, so their absence at the rash stage means nothing. The differentials blur too: rubella has mild coryza, postauricular nodes and a rash clearing in three days; roseola rash appears after the fever breaks; scarlet fever has a sandpaper texture and strawberry tongue without the three Cs.
Frequently asked questions
What are Koplik spots and when do they appear?
Bluish-white spots on an erythematous buccal mucosa opposite the lower molars, pathognomonic, appearing around day two of the prodrome and typically fading as the rash erupts.
How long is a child with measles infectious?
From four days before to four days after rash onset, most contagious during the catarrhal prodrome — which is why outbreaks outrun recognition.
What is the vitamin A regimen in measles?
Two doses 24 hours apart — 50,000 units below six months, 100,000 at 6–11 months, 200,000 at one year and above — with a third dose two to four weeks later where deficiency is common.
Which complication kills most children with measles?
Pneumonia, viral or bacterial, followed by diarrhoea; both are worsened by the immune amnesia that follows infection.
What is subacute sclerosing panencephalitis?
A fatal, years-delayed complication of persistent measles virus in the brain — myoclonus, progressive cognitive and motor decline, and periodic EEG complexes in a child with past measles.
When is the measles vaccine given in India?
MR-1 at nine completed months and MR-2 at 16–24 months under the Universal Immunisation Programme; earlier doses are blunted by maternal antibody.