The prodromal stage of measles is a critical window for early diagnosis and isolation. The pathognomonic finding is Koplik spots: small, irregular red spots with bluish-white centers on the buccal mucosa, opposite the molars. They appear 1–2 days before the characteristic maculopapular rash.
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Assess systematically: Use a good light source and tongue depressor to examine the entire buccal mucosa, especially opposite the lower molars. The spots resemble "grains of salt on a red background."
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Correlate with the 3 Cs: Koplik spots occur alongside cough, coryza (runny nose), and conjunctivitis, with high fever (often 103–105°F). This combination strongly suggests measles even before the rash.
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Initiate infection control immediately: Suspect measles? Place the child in airborne isolation (negative pressure room, N95 respirator) and notify public health. Measles is highly contagious from 4 days before to 4 days after rash onset.
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Differentiate from other viral exanthems: Koplik spots are unique to measles. Mumps presents with parotid swelling; rubella with a fine, lacy rash; varicella with a vesicular, crusting rash.
Key action: Document the presence, location, and description of any oral lesions meticulously. A photograph (with consent) can be invaluable for confirming the diagnosis and educating the healthcare team.