Systemic loxoscelism with hemolysis and positive Coombs: diagnostic and physiopathological implications.

Brown spider (Loxosceles) envenomation is a critical public health issue in Brazil, the systemic cutaneous-hemolytic form of which represents a rare but life-threatening complication. This manifestation is primarily driven by sphingomyelinase D, a potent toxin that triggers a complex cascade of direct erythrocyte membrane disruption and complement-mediated destruction. While systemic cases are more frequently documented in younger populations, reports in octogenarians are exceptionally rare, posing significant diagnostic and therapeutic challenges. This study details a rare case of cutaneous-hemolytic loxoscelism in an 82-year-old woman. Initially misdiagnosed with a primary skin infection, the patient presented four days post-injury with a 6-cm necrotic lesion, fever, and anemia. Laboratory evaluation confirmed a significant hemoglobin drop, elevated lactate dehydrogenase, and a strongly positive direct antiglobulin test (4+), indicating immune-mediated hemolysis. Management included specific antivenom and high-dose corticosteroid therapy (prednisone), leading to clinical stabilization without the need for blood transfusion. The patient was monitored in the intensive care unit with conservative wound management. This report emphasizes that prompt recognition and multidisciplinary intervention are vital for favorable outcomes in rare, high-risk geriatric presentations with prominent synergy between toxic effects and immune dysregulation.