Multifocal and unisystemic Langerhans-cell histiocytosis

This code describes a rare hematologic disorder characterized by the abnormal proliferation of Langerhans cells, affecting multiple sites within a single organ system. It is a form of Langerhans-cell histiocytosis (LCH) that is not disseminated throughout the body.

Assign this code when medical record documentation specifies LCH involving multiple locations but confined to one organ system, such as multiple bone lesions without visceral involvement. Supporting documentation should clearly distinguish it from single-site involvement or widespread systemic disease.

• Differentiate carefully between "unisystemic" and "multisystemic" involvement based on physician documentation.
• Do not code with C96.0 (multifocal and multisystemic LCH) or C96.6 (unifocal LCH) due to Excludes1 notes.
• Ensure the documentation explicitly states "multifocal" and "unisystemic" to accurately apply this code.