Blister (nonthermal) of oral cavity, sequela

This code describes a non-thermal blister located within the oral cavity that is a residual effect or complication of a previous injury or disease. This indicates a long-term consequence rather than an acute presentation of the blister.

Use this code when documentation clearly states a non-thermal oral cavity blister is a sequela, meaning it is a late effect of an earlier condition. This typically applies to chronic or persistent blisters resulting from a past trauma, infection, or other non-thermal etiology.

• Ensure documentation explicitly states the blister is a "sequela" or "late effect" of a prior condition.
• Do not use for acute or current non-thermal oral cavity blisters; those would be coded with the acute S00.522A or S00.522D.
• Always code the underlying cause of the sequela first, if known and still relevant, followed by this code.