Thrombotic microangiopathy, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura: Rare manifestations of Russell’s viper (Daboia russelii) envenoming in Sri Lanka

Background: Russell’s viper (Daboia russelii) of Family Viperidae is a highly venomous snake in Sri Lanka and is responsible for the most snakebite deaths. It commonly causes coagulopathy and neuroparalysis. Thrombotic microangiopathy (TMA) including the triad of acute kidney injury (AKI), thrombocytopenia and microangiopathic hemolysis is a rare complication of its bites. There are two clinical entities of TMA including hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) of which, only few records of TMA and HUS following Russell’s viper bites are available in literature. Case presentation: Two patients presented with TMA following Russell’s viper bites. A 36-year-old male who got coagulopathy, respiratory failure, AKI, signs of HUS, and he completely recovered with antivenom and 8 cycles of hemodialysis and discharged on day 19 of snakebite. The other patient was a 66-year-old female who had delayed coagulopathy and persistent drowsiness, the signs of TTP. She required antivenom with 9 cycles of hemodialysis and 6 cycles of therapeutic plasma exchange and got recovered after 30 days in hospital that included intensive care treatments. Discussion: Russell’s viper venom causes activation of Factor V and X which results venom induced consumption coagulopathy and bleeding. The venom also blocks neuromuscular junction and causes neuroparalysis, which are commonly manifested as ptosis and external ophthalmoplegia. It also has direct nephrotoxic effects and there are fibrin depositions in renal microvasculature thereby, causing renal ischemia. In the spectrum of HUS-TTP of TMA, HUS is suggested when there is a severe renal involvement, and TTP is diagnosed when neurological impairment is prominent. Conclusion: Atypical presentations like TMA and HUS may rarely occur following Russell’s viper bites. Further evidence of similar observations is needed to confirm the clinical entity of TTP following Daboia russelii bites.