Introduction:
Atypical Hemolytic Uremic Syndrome (aHUS) is clinically defined by microangiopathic hemolytic anemia, progressive acute renal failure and thrombocytopenia. The most common triggering factors leading to aHUS are pregnancy, infections. Other uncommon triggers include immunosuppressive drugs, cancer therapies, oral contraceptives, childbirth, snake bite. Hereby we report a case of primary atypical HUS triggered by snake bite.
Methods:
A 31 year old male, nil premorbid, had a history of snake bite on left ankle. He was treated with injection tetanus toxoid and other symptomatic treatment at a nearby health center. He presented the following day, approximately 24 hours after the snake bite. At time of presentation, patient vitals were hemodynamically stable and he had a left lower limb cellulitis with inflammation extending upto knee. There was no active bleeding from the local site or elsewhere, and no neurological deficit was noted. He had complaints of decreased urine output for 1 day (Urine output was noted to be <0.3ml/kg/hour). Initial laboratory data had shown renal failure with serum creatinine of 4.7mg/dl. Complete hemogram showed neutrophilic leukocytosis and mild thrombocytopenia. Coagulation profile was sought and was deranged. Clinical features and laboratory analysis were suggestive of venom associated consumption coagulopathy (VICC). Differential diagnoses of sepsis, hemolysis, disseminated intravascular coagulation were considered. He was managed with anti snake venom (ASV), FFP transfusions 20 ml/kg day 1, followed by 15 ml/kg daily), empirical antibiotics and hemodialysis. However, he had persistent thrombocytopenia even after 1 week and snake envenomation signs had resolved. On further evaluation peripheral smear showed schistocytes and there was recurrent rise in LDH. Considering the possibility of underlying alternate pathway dysregulation, renal cortical necrosis, C3 glomerulopathies, a renal biopsy was done, which had showed patchy cortical necrosis secondary to thrombotic microangiopathy (TMA) in light microscopy, and sample for immunofluorescence had no glomeruli and so was inadequate. Alternate complement pathway analysis was done. Anti CFH antibody was positive (235.2 AU/ml, Normal - <20 AU/ml). Complement genotyping for aHUS was not done as it is not available. 3 sessions of plasmapheresis were done with FFP replacement. LDH and platelets had improved and stabilized. Patient had improved and had been under regular follow up and had no further episodes.
Results:
Conclusions:
Currently HUS can be divided into primary and secondary. Primary HUS includes the cases without any coexisting diseases, most commonly due to complement dysregulation. While the latter are due to secondary causes. aHUS due to genetic mutations behaves like a two hit hypothesis or multiple hit hypothesis which get triggered by many risk factors disrupting complement homeostasis. Anti factor H autoantibodies lead to blocking of the factor H which regulates the alternate complement pathway leading to dysregulation of complements. Some recent studies had indicated that patients developing anti factor H autoantibodies had association with correlate with CFHR1/CFHR3 deficiency, implying deficient innate immune deficiency which gets dysregulated by risk factors. Our patient had a snake bite and following which he had developed venom induced consumptive coagulopathy, had been appropriately treated with ASV (anti snake venom) and hemodialysis for the acute renal failure. Despite initial improvement there was persistent thrombocytopenia which had not recovered and on further evaluation found out to have underlying thrombotic microangiopathy mechanism activated. So plasmapheresis was considered and he had improved clinically following 2 cycles, without any administration of newer drugs like Eculizumab which had shown significant benefit in most of the studies.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.