A 9-month-old with fever of 103 F for 2 days develops a diffuse maculopapular rash that blanches. Immunizations are up to date. What is the appropriate management?

A 9-month-old with fever of 103 F for 2 days develops a diffuse maculopapular rash that blanches. Immunizations are up to date. What is the appropriate management?

• A. Administer immunoglobulin G to prevent fulminant illness.
• B. Perform serologic testing for human herpes virus 6 and 7.
• C. Reassure the parent that this is a mild, self-limiting disease.
• D. Recommend avoiding contact with pregnant women.

Answer: (B)

This presentation is most characteristic of roseola infantum, caused by human herpesvirus 6 (often with 7) in children under two. The pattern—high fever for several days followed by a diffuse, blanching maculopapular rash as the fever resolves—fits well, and up-to-date immunizations help rule out other exanthems like measles or rubella. The best next step among these options is to perform serologic testing for HHV-6 and HHV-7 to confirm the etiology. While the illness is typically self-limited and managed with supportive care (fever control, fluids), identifying the causative virus can provide a definitive diagnosis, reassure families, and distinguish roseola from other febrile exanthems. The other options introduce unnecessary or inappropriate actions: IVIG is not indicated for roseola; simply reassuring without any consideration of confirming the cause may miss an opportunity to document the diagnosis; and advising avoidance of pregnant women isn’t necessary for this common, usually benign infection.

This presentation is most characteristic of roseola infantum, caused by human herpesvirus 6 (often with 7) in children under two. The pattern—high fever for several days followed by a diffuse, blanching maculopapular rash as the fever resolves—fits well, and up-to-date immunizations help rule out other exanthems like measles or rubella.

The best next step among these options is to perform serologic testing for HHV-6 and HHV-7 to confirm the etiology. While the illness is typically self-limited and managed with supportive care (fever control, fluids), identifying the causative virus can provide a definitive diagnosis, reassure families, and distinguish roseola from other febrile exanthems. The other options introduce unnecessary or inappropriate actions: IVIG is not indicated for roseola; simply reassuring without any consideration of confirming the cause may miss an opportunity to document the diagnosis; and advising avoidance of pregnant women isn’t necessary for this common, usually benign infection.