Fig. 1

The Clinical course of case 1. We present the clinical course of an HTLV-1-positive recipient (Case 1) who underwent renal transplantation at our institution (Table 3, Fig. 1). A 65-year-old male was diagnosed with end-stage kidney disease (ESKD; unknown etiology) in 2012 and subsequently underwent renal transplantation in July 2017. The patient was an HTLV-1 carrier prior to renal transplantation. The patient underwent a living renal transplant from his wife, who had HLA mismatch and blood type incompatibility. After the renal transplantation, immunosuppressive therapy with FK was administered. In April 2020, the skin rash had worsened throughout the body. Skin biopsy revealed ATL, suggesting monoclonal proliferation of ATL cells. Furthermore, chest CT showed glass shadows scattered in both lungs, suggesting the infiltration of ATL cells. Taking these findings together, we made a diagnosis of lymphoma-type ATL, an extranodal primary cutaneous variant, according to a report by Tsukasaki et al. [40]. Thus, case 1 developed ATL 2 years and 9 months after renal transplantation. Immunosuppressants for FK were used to prevent rejection by kidney transplantation. Regarding FK trough concentration in PB just prior to develop ATL, the blood levels of FK in the renal transplant recipient (case 1) were 5.5 ng/mL (FK 3.0 mg per day). FK withdrawal was performed from 3.0 mg per day to 2.0 mg per day. Thus, in April 2020, FK tapering and subsequent CHOP therapy were initiated. After three courses of CHOP therapy, the skin rush/lung lesions showed PR. To date, there has been only one report by Mori et al. [41] on allo-HSCT for the development of Ph1 + ALL after liver transplantation. According to Mori's report [41], we performed cord blood stem cell transplantation (CBSCT) using a conditioning regimen including FLU/MEL/TBI and graft-versus-host disease (GVHD) prophylaxis with FK plus MMF. On day 11, chest computed tomography (CT) revealed lung infiltration with a reversed halo sign in the right lung lobe and hematoma in the anterior chest and mediastinum. Rhizopus microspores and Mucor Zygomycetes from anterior chest hematomas were identified. On day 14, the patient developed septic shock and acute respiratory and renal failure. Therefore, the patient was treated with intubation and CHDF in the ICU. However, on day 16, the patient died of multiple organ failure (MOF) progression