What would indicate a diagnosis of toxic epidermal necrolysis instead of Stevens-Johnson syndrome?

Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are both severe reactions characterized by skin and mucous membrane detachment, but they are differentiated primarily by the extent of body surface area affected. A diagnosis of TEN is typically identified when there is more than 30% of the body's surface area involved in the skin detachment process. In contrast, SJS is diagnosed when less than 10% of the body surface area is affected.

The distinction hinges on the severity of the skin damage. In TEN, the extensive damage leads to significant complications and a higher risk of mortality, which is not as pronounced in cases of SJS. Therefore, understanding the percentage of total body surface area affected is crucial for the diagnosis and management of these conditions, making it the key factor in differentiating between them.