Background/Purpose: Human T-lymphotropic virus type-I (HTLV-1) is a retrovirus associated with Adult T-cell leukemia (ATL) that is commonly seen in endemic areas. Several case reports suggest that immunosuppressants, including biologic agents, may be related to development of ATL in HTLV-I carriers. The purpose of this study was to evaluate the risk for developing ATL in HTLV-1 carriers who received immunosuppressive therapy for rheumatic or inflammatory bowel diseases, or cancer.

Methods: Medical records were reviewed at Okinawa Chubu Hospital to locate all HTLV-1+ patients from 2010 to 2013. After excluding 8 renal transplant patients, there were 727 HTLV-1+ patients. Incidence and progression of ATL were compared between subjects with and without immunosuppressive therapy. Data were collected on clinical features, medications and peripheral smears.

Results: We identified 83 HTLV-1+ subjects who received immunosuppressive therapy, including prednisolone, disease-modifying anti-rheumatic drugs (DMARDs) or biologic agents: 52/83 (64%) had rheumatic diseases. 90 subjects (12%) had non-ATL malignancy including solid cancer and hematological malignancy with or without chemotherapy (Table). Median observation period was 26 months (2-50) in patients receiving immunosuppressive therapy, and 26 months (2-50) in controls. Incidence of ATL did not differ between subjects on and off immunosuppressive therapy (P=0.6). In 7 patients on biological agents (5 etanercept, 1 infliximab and 1 abatacept), no ATL occurred during the observation period (median 22 months, range 9-50).

Conclusion: No cases of ATL developed among HTLV-1+ patients on immunosuppressants over an observation period of 26 months. Immunosuppressive therapy may not promote development of ATL in HTLV-1+ patients with rheumatic diseases.