Multifocal and multisystemic Langerhans-cell histiocytosis

This code describes a rare, aggressive form of Langerhans cell histiocytosis (LCH) characterized by the proliferation of abnormal Langerhans cells affecting multiple organ systems throughout the body. It signifies widespread disease involvement, distinguishing it from more localized forms of LCH.

Use this code when documentation clearly indicates LCH with involvement in two or more distinct organ systems, such as bone, skin, liver, spleen, lymph nodes, or hematopoietic system. This diagnosis is typically confirmed by biopsy showing Langerhans cells and often requires extensive diagnostic workup to determine the extent of systemic involvement.

• Carefully review documentation to confirm involvement in multiple distinct organ systems to differentiate from unisystemic or unifocal forms.
• Be mindful of the Excludes1 notes; do not code this alongside adult pulmonary LCH, multifocal and unisystemic LCH, or unifocal LCH.
• Ensure the medical record specifies "multifocal and multisystemic" or provides sufficient detail to infer widespread systemic involvement.