What are the clinical manifestations of measles, particularly in pediatric patients?

Clinical Appearance of Measles

Measles presents with a characteristic maculopapular rash that begins on the face and spreads downward to the trunk and extremities, preceded by fever, cough, runny nose (coryza), and conjunctivitis. 1

Prodromal Phase (Before the Rash)

The disease begins with a prodromal period that occurs approximately 10-12 days after exposure, characterized by: 1

• High fever 2
• Cough 1
• Coryza (runny nose) 1
• Conjunctivitis ("pink eye") 1

Pathognomonic Sign

• Koplik spots appear during the prodrome—these are small white spots on a red background inside the mouth (on the buccal mucosa) and are considered pathognomonic (uniquely characteristic) for measles 3, 1
• These spots provide an opportunity to diagnose measles even before the rash emerges 4

Rash Phase

The rash typically appears 3-4 days after fever onset (approximately 14 days from initial exposure): 1, 4

• Maculopapular or morbilliform appearance (flat red spots with raised bumps) 3
• Distribution pattern: Begins on the face and behind the ears, then spreads downward to the trunk and outward to the extremities 3, 1, 4
• The appearance of the rash coincides with the peak of symptoms 4

Contagious Period

Patients are contagious from 4 days before the rash appears until 4 days after the rash onset 3, 2—this is a critical pitfall, as patients can spread measles before they are visibly identifiable.

Common Pitfalls in Recognition

• Subclinical presentations: In immunocompromised individuals, measles may present without the typical rash, making diagnosis more challenging 1
• Modified measles: In previously vaccinated individuals who experience vaccine failure, the presentation may be atypical, though complications occur at similar rates 5
• Early dismissal: The prodromal symptoms alone (fever, cough, runny nose, red eyes) may be mistaken for a common cold before the characteristic rash appears 4