Mamushi bites in a kidney transplant recipient

Introduction Mamushi bites are the most common venomous snakebites in Japan. The clinical course of a common mamushi bite is known, and its alarming complication and cause of death are acute renal failure due to the venom. However, reports of mamushi bites in kidney transplant recipients are lacking, and the clinical course is unknown. Case presentation A 66‐year‐old man who was bitten by a mamushi 3 years after kidney transplantation. Similar to the course of a typical mamushi bite, his severity gradually worsened to its peak 3 days after the bite, after which he turned lightly. A sufficient amount of infusion and continued immunosuppressive drugs were used to avoid acute renal failure. Conclusion Even if the mamushi bite occurs in a kidney transplant recipient, the course and management may be the same as usual by continuing the immunosuppressive drugs and a sufficient amount of infusion.


Case presentation
A 66-year-old man, stable 3 years after kidney transplantation in our hospital, felt a tingling pain in his right index finger while weeding a field in the evening of late August and confirmed a mamushi nearby. He was admitted to our hospital immediately. Characteristics, such as two parallel fang marks with dark purple bleeding foci under the skin, were found on his right index finger. The redness and swelling were just localized to the right hand. Upon arrival at the hospital, his consciousness was clear, with a blood pressure of 140/70 mmHg, pulse of 70 beats per minute, body temperature of 36.5°C, and SpO 2 of 99% under room air. He did not report double vision.
The administration of lactated Ringer's solution infusion (3000 mL/day), cepharanthin, antibiotics, and TT was initiated according to the dosage stated in the package insert. However, due to his strong allergic reaction to the manufactured mamushi antivenom, it could not be administered. Tacrolimus, mycophenolate mofetil, and methylprednisolone, which had been used as immunosuppressive drugs after kidney transplantation, were continued at their prescribed doses.
After admission, the area of redness and swelling continued to expand, and on the third day, these areas extended to the chest and diplopia appeared. We determined that the MB grade worsened to V. Similarly, laboratory data suggested rhabdomyolysis with a high CPK level (Fig. 1). The severity grade worsened, but the same treatments were continued.
Fortunately, however, urine output and renal function were adequately maintained.
After the fourth hospital day, MB grade and biochemical results of the blood gradually improved. He was discharged on hospital day 14 without any deterioration of renal function or infection or any signs of disseminated intravascular coagulation.

Discussion
This patient course provided two important clinical suggestions.
First, this case followed the same clinical course as previously reported general MB patients: a severe peak of MB grade, rhabdomyolysis with a high CPK level, widespread edema extending to dryness, and diplopia 3 days after MB. 1-8 These were gradually relieved over the next 10 days. [1][2][3][4][5][6][7][8] Therefore, this case suggests that it is possible to treat MBs in KTRs according to the severity reported before and predict the clinical course. [1][2][3][4][5][6][7][8] Grade classification for MBs 1-8 is clinically used to determine the severity of injuries as follows: Grade I, redness and swelling localized at the bitten area; Grade II, redness and swelling limited to the wrists and ankles; Grade III, redness and swelling limited to the elbow or knee joint; Grade IV, redness and swelling of the whole extremity; and Grade V, redness and swelling in parts beyond the extremity or exhibiting systemic symptoms including diploma. The manufactured mamushi antivenom treatment is definitive and recommended for Grade III or higher defined as severe. 1 Second, this case did not need to reduce or discontinue immunosuppressive drugs.
Mamushi venom is a variety of enzymes that act directly on vascular permeability, muscle, platelets, and nerves, and it is speculated that immunosuppression by immunosuppressive drugs does not enhance the effect of mamushi venom. Since in general, rejection is the main cause of renal transplant loss, KTRs should not discontinue immunosuppressive drugs unless they have a malignant tumor or an uncontrollable infectious disease. 9 Additionally, KTRs are in a chronic kidney disease state and are prone to renal damage due to dehydration. 9 From the viewpoint of preventing acute renal failure, immunosuppressive drugs should be continued even in severe MB case, and a sufficient amount of infusion is required to prevent rejection and dehydration. So far, no special infection has been found in patients who have MBs reported before, and administering TT in all cases is unnecessary. 8 In our case, despite the severe case in which the manufactured mamushi antivenom could not be administered, the disease improved without renal failure as complication and rejection with continued immunosuppressive drug and sufficient infusion. The clinical course was almost the same as a general MBs.

Conclusion
KTRs with MB followed a similar clinical course as general MB patients and did not require dose reduction or discontinuation of immunosuppressive drugs during treatment. In the future, it is possible that a new KTR with MB will occur. Our case should be considered a valuable report for treating KTRs with MB. Thus, it is necessary to accumulate case reports, such as our cases.