ICD-10 Code B08.21 – Exanthema subitum [sixth disease] due to human herpesvirus 6 (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code B08.21 – Exanthema subitum [sixth disease] due to human herpesvirus 6
What it is
B08.21 identifies roseola, also called exanthema subitum, when documentation links it to human herpesvirus 6. Use it for the specific viral cause, not for an unspecified febrile rash illness.
Clinical signs
Typical findings include a sudden high fever followed by a pink maculopapular rash as the fever resolves. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents roseola, sixth disease, or exanthema subitum due to human herpesvirus 6. It also fits records that explicitly name HHV-6 as the cause. If the chart only says viral exanthem or fever with rash, check documentation before coding.
Do not use for
Do not use it for exanthema subitum without a documented HHV-6 cause. Avoid it when the diagnosis is a different viral exanthem or when the record is too vague to support this specific code.
Coding tip
Code B08.21 only when the provider clearly ties sixth disease to human herpesvirus 6 in the record.