Febrile Maculopapular Exanthem Associated with Influenza a Subtype H3N2 Viral Infection: A Rare Manifestation and a Review of the Literature

Background: Influenza A-associated cutaneous manifestations are rare in adults and are poorly characterized, especially in infections, due to seasonal H3N2 strains. Awareness of influenza-related exanthems is clinically important because misdiagnosis may delay antiviral therapy and broaden unnecessary investigations.

Case presentation: We report a case of a previously healthy 21-year-old man presenting with high-grade fever, pharyngitis, non-pruritic maculopapular rash, and pronounced lymphopenia. An influenza A/H3N2 infection was identified by rapid antigen testing and multiplex respiratory PCR. Further investigation ruled out other viral and bacterial infections, as well as medications, as a cause of the exanthem. He had a rapid clinical improvement with oseltamivir therapy, with complete resolution of fever and significant regression of rash by day 5.

Discussion: Adult-onset maculopapular exanthems associated with influenza A infection are rare and might closely resemble other viral exanthems, hypersensitivity reactions, or streptococcal diseases. This case broadens the dermatologic spectrum of influenza A/H3N2 and highlights the need to consider influenza as a cause of febrile rash syndromes during epidemic seasons. Review of the literature shows limited, but consistent, documentation of similar presentations, mainly attributed to H1N1 strains.

Conclusion: Influenza A/H3N2 infection should be considered in the differential diagnosis of acute febrile maculopapular rash in adults. Early antiviral therapy may promote rapid clinical improvement and avoid unnecessary procedures. This case underscores the need for greater recognition of dermatologic manifestations related to influenza infection in order to enhance diagnostic precision and patient care.