Clinical Spectrum of Febrile Rash Illnesses in Children: A Hospital-Based Case Series Highlighting Diagnostic Challenges in Measles and Mimicking Conditions

Background: Measles remains one of the most contagious viral diseases despite the availability of highly effective vaccines. Although two-dose measles vaccination provides protection exceeding 95%, sporadic breakthrough infections continue to be reported, particularly in settings approaching measles elimination. Such cases pose important diagnostic and public health challenges because clinicians may have a lower index of suspicion in vaccinated individuals. We describe a cluster of pediatric febrile rash illnesses that included laboratory-confirmed measles in both a fully immunized adolescent and an unimmunized child.

Case Series: Four pediatric patients presented within a short temporal window with fever, respiratory symptoms, and generalized rash. Two cases demonstrated positive measles IgM serology. The first was a 14-year-old fully immunized male who developed fever, cough, pharyngitis, and rash with positive measles IgM and mild transaminitis. The second was an unimmunized 7-year-old female presenting with the classic measles prodrome of cough, coryza, conjunctivitis, and rash, also with positive measles IgM. Two additional fully immunized children developed clinically compatible febrile exanthematous illnesses but tested negative for measles IgM. Alternative etiologies including dengue and malaria were excluded.

Conclusion: This cluster illustrates three important contemporary challenges: (i) occurrence of laboratory-confirmed measles despite complete immunization, (ii) persistence of susceptible individuals due to immunization gaps, and (iii) diagnostic uncertainty associated with serologically negative but epidemiologically linked cases. The findings underscore the need for continued vigilance, robust surveillance systems, and recognition of breakthrough measles during the measles elimination era.