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Paper text:
if viper bites are well known in france with recent epidemiological studies and official protocols for the treatement , pulmonary embolism is an exceptional complication of human envenomations induced by european vipers .
we report the interesting case of a bilateral pulmonary embolism following a viper bite in french western coast .
a 72-year - old female was admitted to the emergency department with a swollen leg , after a snake bite on her right foot while walking in the countryside , on the french western coast .
the scar with 2 points confirmed it was the fang marks of a viper . the leg swill immediately and she came to the emergency department 48  hours after , because of an extensive hematoma on her calf and thigh .
she had no prior significant medical and gynecological troubles , and no history of neoplasia or thrombosis .
complete bilateral doppler powered ultrasound ( us ) at admission did not show any lower limbs thrombosis .
blood tests showed no disseminated intravascular coagulation ( dic ) ( table 1 ) ; she had no clinical or biological signs of rhabdomyolysis or renal failure .
she received daily preventive low - molecular - weight heparin injections ( enoxaparin 4000 iu / day ) and lower limb compression device was prescribed .
initial biological findings of our patient seven days after admission , the hematoma started to heal although she presented acute thoracic pain and dyspnea ; computed tomography angiogram showed a bilateral pulmonary embolism .
blood test ( troponin and coagulation factors ) and second complete bilateral lower limbs doppler us were still normal . a complete examination and
she healed rapidly with low - molecular - weight heparin ( enoxaparin with a weight - related dosage of 12,000 iu / day ) and oxygen therapy ( 23 l / min ) .
then she received warfarin and compression stockings for 6 months . during the 18-month follow - up
, she did not present any other hemorrhagic or thrombotic episode . at the end of follow - up ,
lower limb doppler us , coagulation blood tests , and pulmonary function were strictly normal .
ethical approval was not necessary because all data were collected anonymously , and the patient gave her consent for publication .
usually , snake envenomations lead to pain , swelling , and moderate hemorrhagic symptoms . in many countries ( in africa , australia , and south america )
, snakes can cause death because of neurotoxicity , rhabdomyolysis , or severe coagulopathy causing necrosis or disseminated hemorrhage .
several species ( viperidae , crotalidae , elapidae , and colubridae ) can also be responsible for haemostatic troubles . in french western coast
only 2 species of viper can be seen : vipera aspis , which is more common and vipera berus .
venom from viperidae has an effect on coagulation , that is why hemorrhagic complications are common and heparin treatment is not recommended during the acute phase of envenomation . in contrast , thromboembolic complications are very rare but can be seen during the later phase of envenomation .
to our knowledge , only 4 others cases of pulmonary embolism following viper envenomation have been described so far .
pulmonary embolism also occurred exactly 1 week after the bite , without associated phlebitis and after a previous subcutaneous hematoma .
however , dic syndrome was described in all 3 cases , with decreased fibrinogen and elevated activated partial thromboplastin time ( aptt ) ratio .
one more envenomation case was caused by greek viper on a child who suffered from diamond  blackfan anemia .
we found out 2 other cases in the literature : the first one occurred in martinique ( french west indies ) was because of bothrops lanceolatus , whose venom is responsible for acute thromboembolic complications in 30% cases . in this case , pulmonary embolism happened a few hours after the bite , suggesting a different way of hypercoagulation activation .
the second one was because of crotalus scutulatus , an american snake . in this case , baghat et al described an interesting case of dic syndrome with decreased levels of fibrinogen .
several hypotheses have been made to explain this late coagulopathy causing localized thromboembolism after snake bites .
first , hypercoagulability could be caused by an increased systemic inflammation starting a few days after the bite , biologically showed by increased prothrombotic factors ( fibrinogen and thrombocytosis ) .
all published cases of pulmonary embolism following envenomation had no associated lower limb thrombosis , which suppose a complex localized hypercoagulability .
it is also important to note that thrombosis usually occurs at some distance from the site of bites .
other hypotheses are more complex : venoms contain molecules directed against several targets of a coagulation pathway .
for example , thrombin - like protease with initial fibrinolytic activity could cleave fibrinopeptide a or b from fibrinogen and activate coagulation factors , resulting in a cross - linked fibrin clot .
dic - like syndrome ,  without real biologic dic : coagulation factors , d - dimer levels , and antithrombin 3 are usually normal .
a  localized coagulopathy  appears because of increased levels of unstable fibrin produced by thrombin - like glycoproteins from the venom . in conclusion
, we reported an extremely rare case of envenomation following viper bite in france , responsible for a late bilateral pulmonary embolism .
our case is atypical because the patient had normal levels of fibrinogen , aptt , inr , and platelet counts , whereas in chani cases and baghat case patients had dic - like syndrome with low levels of fibrinogen .
however , delay between the bite and happening of pulmonary embolism was similar between our case and all described cases .
so far , heparin is not recommended in the acute phase of envenomation because of initial hypocoagulability , but could be useful once hemorrhagic symptoms improve .
in french western coast only 2 species of viper can be seen : vipera aspis , which is more common and vipera berus . venom from viperidae
has an effect on coagulation , that is why hemorrhagic complications are common and heparin treatment is not recommended during the acute phase of envenomation . in contrast , thromboembolic complications are very rare but can be seen during the later phase of envenomation . to our knowledge
, only 4 others cases of pulmonary embolism following viper envenomation have been described so far .
pulmonary embolism also occurred exactly 1 week after the bite , without associated phlebitis and after a previous subcutaneous hematoma .
however , dic syndrome was described in all 3 cases , with decreased fibrinogen and elevated activated partial thromboplastin time ( aptt ) ratio .
one more envenomation case was caused by greek viper on a child who suffered from diamond  blackfan anemia .
we found out 2 other cases in the literature : the first one occurred in martinique ( french west indies ) was because of bothrops lanceolatus , whose venom is responsible for acute thromboembolic complications in 30% cases . in this case , pulmonary embolism happened a few hours after the bite , suggesting a different way of hypercoagulation activation .
the second one was because of crotalus scutulatus , an american snake . in this case ,
baghat et al described an interesting case of dic syndrome with decreased levels of fibrinogen .
several hypotheses have been made to explain this late coagulopathy causing localized thromboembolism after snake bites .
first , hypercoagulability could be caused by an increased systemic inflammation starting a few days after the bite , biologically showed by increased prothrombotic factors ( fibrinogen and thrombocytosis ) .
all published cases of pulmonary embolism following envenomation had no associated lower limb thrombosis , which suppose a complex localized hypercoagulability .
it is also important to note that thrombosis usually occurs at some distance from the site of bites .
other hypotheses are more complex : venoms contain molecules directed against several targets of a coagulation pathway .
for example , thrombin - like protease with initial fibrinolytic activity could cleave fibrinopeptide a or b from fibrinogen and activate coagulation factors , resulting in a cross - linked fibrin clot .
dic - like syndrome ,  without real biologic dic : coagulation factors , d - dimer levels , and antithrombin 3 are usually normal .
a  localized coagulopathy  appears because of increased levels of unstable fibrin produced by thrombin - like glycoproteins from the venom . in conclusion
, we reported an extremely rare case of envenomation following viper bite in france , responsible for a late bilateral pulmonary embolism .
our case is atypical because the patient had normal levels of fibrinogen , aptt , inr , and platelet counts , whereas in chani cases and baghat case patients had dic - like syndrome with low levels of fibrinogen .
however , delay between the bite and happening of pulmonary embolism was similar between our case and all described cases .
so far , heparin is not recommended in the acute phase of envenomation because of initial hypocoagulability , but could be useful once hemorrhagic symptoms improve .
abstractcomplications following snake bites are not common in france . 
 we report the case of a bilateral pulmonary embolism following a viper envenomation in france.a healthy 72-year - old female presented with a lower limb hematoma following a viper bite . 
 she was admitted at the hospital 2 days later and received low - molecular - weight heparin because of bed rest . 
 seven days later , she complained of thoracic pain and respiratory failure , and a bilateral pulmonary was diagnosed , without biological sign of neither disseminated intravascular coagulation nor coagulation trouble . 
 repeated lower limbs doppler ultrasound were normal.this case is particularly interesting because it is only the 7th reported case of pulmonary embolism following a snake envenomation ; moreover , it happened in france where poisonous snakes are very rare.several hypotheses have been made to explain this late localized coagulopathy : an increased level of unstable fibrin produced by thrombin - like glycoproteins from the venom is one of them .