Arthus phenomenon, subsequent encounter

This code represents an immune complex-mediated hypersensitivity reaction, specifically a localized tissue necrosis resulting from repeated exposure to an antigen. It is characterized by inflammation, edema, and hemorrhage at the site of antigen injection, often appearing hours after exposure.

Use this code for follow-up encounters when a patient is being treated for or monitored for an Arthus phenomenon. This includes visits for symptom management, wound care, or assessment of healing after the initial acute reaction has been addressed.

• Requires a seventh character "D" for subsequent encounter.
• Do not use for the initial presentation of the Arthus phenomenon; refer to the "A" seventh character for initial encounter.
• Code any associated complications (e.g., skin necrosis, infection) separately.