The patient was a 49-year-old man with chronic renal insufficiency. He underwent right renal transplantation in the Chinese People's Armed Police Force General Hospital in November 2016. Following transplantation, the patient underwent immunosuppression therapy, which included tacrolimus, prednisone, and myfortic, resulting in the return of normal renal function in the patient.
Two years later, the level of sCr in the patient gradually increased from normal to 274 mmol/L during routine laboratory testing. Enhanced MRI demonstrated multiple, variably sized quasi-circular lesions with slightly short signal intensity on T1WI, slightly long signal intensity on T2WI, and high signal intensity on DWI. The larger size lesion was about 4.66 cm by 3.10 cm (Fig. 1). PET-CT revealed a soft tissue mass in the pelvis of the transplanted kidney (with an elevated SUV of 2.6), and multiple metastatic hypermetabolic soft tissue density nodules can be observed in the parenchyma of the transplanted kidney (with a maximum SUV of 2.9). No metastatic hypermetabolic lesions were observed in any other parts of the body.
A puncture biopsy of the transplanted kidney was performed, and the results indicated large neoplastic cells. The immunohistochemistry examination revealed the following: CD34 (few +), CD68 (KP1) (few +), CD163 (-), lysozyme (few +), MPO (+), Ki-67 (༞70% +), CD3 (few +), CD20 (-), TdT (few +), CD15 (-), CD117 (+), FISH: EBER(-). Bone marrow biopsy showed no evidence of leukemic infiltration (Fig. 2), with normal chromosomes (46, XY). Examinations of fusion genes for both acute lymphoblastic leukemia and myeloid leukemia were negative. NGS examinations of the transplanted kidney was performed on 34 commonly mutated genes in AML (listed in Supplementary Table) and showed mutations of KRAS (NM_004985:exon2:c.G35A:p.G12Drs121913529), DNMT3A (NM_022552:exon15:c.1675delT:p.C559fs), and no gene mutations in the bone marrow. Eventually, the patient was diagnosed with de novo MS in the transplanted kidney. Detailed information on the donor was not available, but the other transplant recipient did not have any problems in the transplanted kidney.
The patient underwent systemic chemotherapy in our hospital in October 2019, and received DA regimen chemotherapy (daunorubicin 100 mg on days 1–3 and cytarabine 170 mg on days 1–7). The patient responded well to the treatment, and the size of the mass in the transplanted kidney decreased and the level of sCr decreased to 192 mmol/L. The patient underwent a second cycle of DA regimen chemotherapy 30 days later. The size of the biggest lesion decreased to 2.5cm by 1.8cm, but the level of sCr remained at around 180 mmol/L. Therefore, we changed the chemotherapy regimen to cytarabine 2.5 g every 12h on days 1, 3, and 5, and etoposide 100 mg on days 1–3 for 3 cycles. However, 3 days after the 5th cycle of the revised chemotherapy regimen, the patient presented with progressive generalized motor weakness and slurred speech, without headache and vomiting, and the patient couldn’t stand and walk without assistance. A routine blood test showed WBC 4×109/L, NEUT 3.84×109/L, HGB 94.3 g/L, and PLT 44×109/L. The patient’s liver function, serum ions, and other metabolic panels were within normal limits, except that the level of sCr was 157 mmol/L. Head CT and MRI did not show any new abnormal acute findings, and it was presumed that the neurologic symptoms experienced by the patient were a result of cytarabine neurotoxicity. Thereafter the patient was treated with prednisone 40 mg twice a day for 3 days, which led to a significant improvement in his symptoms. After recovering from the neurologic symptoms, the patient refused to continue chemotherapy and allogeneic hematopoietic stem cell transplantation. The patient was followed up on April 20, 2021 and he could speak fluently, but sometimes walked with an unsteady step. The size of the biggest lesion in the transplanted kidney decreased to 1.7 cm and the level of sCr was maintained at around 200mol/L.