ICD-10 Code L51.9 – Erythema multiforme, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code L51.9 – Erythema multiforme, unspecified
What it is
L51.9 identifies erythema multiforme when the record does not specify a more detailed type. It is used for a hypersensitivity-related skin eruption with target-like lesions, but the documentation is nonspecific.
Clinical signs
Typical findings include sudden-onset target or iris lesions, often on the extremities, with possible mucosal involvement. Clinical features vary; refer to documentation.
When to use this code
Use L51.9 when the clinician documents erythema multiforme without naming a subtype or cause. It also fits when notes describe the condition generally, but do not support a more specific ICD-10 option. If the record identifies a related disorder more precisely, code that instead.
Do not use for
Do not use this code for Stevens-Johnson syndrome, toxic epidermal necrolysis, or other clearly documented blistering drug reactions. Check documentation if the eruption is described with a different diagnosis.
Coding tip
Query for lesion pattern and any documented trigger before assigning the unspecified code.