Erythema nodosum

This code represents an inflammatory condition characterized by tender, red, subcutaneous nodules, typically located on the shins. It is a panniculitis, meaning inflammation of the subcutaneous fat, and is often a reactive process to various underlying systemic conditions, infections, or medications.

Use this code when documentation specifies erythema nodosum as the primary diagnosis or a significant co-morbidity. This applies when the physician identifies the characteristic skin lesions and attributes them to a non-tuberculous etiology. Supporting documentation should include a description of the lesions and their location.

• Always review documentation to rule out a tuberculous etiology, as this would lead to a different code (A18.4).
• Code any underlying conditions (e.g., sarcoidosis, inflammatory bowel disease, streptococcal infection) as additional diagnoses.
• Do not use this code for other forms of panniculitis unless specifically documented as erythema nodosum.