HTLV-I as the cause of diseases classified elsewhere

This code identifies HTLV-I as the underlying etiology for conditions that are primarily classified in other chapters of ICD-10-CM. It signifies that a disease process, such as certain lymphomas, leukemias, or neurological disorders, is directly attributable to an HTLV-I infection. This is a "manifestation code" indicating the cause of another disease.

Use this code when medical record documentation clearly states that HTLV-I is the causative agent of a specified disease. This typically applies to conditions like Adult T-cell Leukemia/Lymphoma (ATLL) or HTLV-I Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). Documentation must explicitly link the HTLV-I infection to the patient's primary diagnosis.

• Always sequence this code after the code for the specific disease caused by HTLV-I.
• Do not use this code for asymptomatic HTLV-I carrier status; use Z22.6 for that.
• Ensure documentation specifies "HTLV-I" and not just "HTLV" to avoid confusion with HTLV-II.