A Rare Atypical Cardiac-Arrest Onset of Fulminant Systemic Lupus Erythematosus with Multiorgan Failure, Myocarditis, and AMAN- Variant Guillain-Barré Syndrome Successfully Treated with Multimodal Immunotherapy.

BACKGROUND: This report highlights a rare, catastrophic presentation of Systemic Lupus Erythematosus (SLE) manifesting as sudden cardiovascular collapse in a patient with no prior autoimmune history. The case is particularly novel due to the concurrent development of the Acute Motor Axonal Neuropathy (AMAN) variant of Guillain-Barré Syndrome (GBS) alongside multiorgan failure, mimicking septic and cardiogenic shock. CASE PRESENTATION: A 49-year-old woman suffered an out-of-hospital cardiac arrest following acute gastroenteritis, characterized by recurrent ventricular fibrillation and tachycardia. She rapidly developed multiorgan failure, including severe myocardial dysfunction (EF 29%), acute kidney injury, metabolic acidosis, and altered consciousness. While the initial presentation suggested sepsis, subsequent testing revealed positive antinuclear antibodies, lupus anticoagulant, and hypocomplementemia, meeting ACR/EULAR criteria for SLE. Electrophysiological studies for persistent weakness confirmed AMAN-type GBS. Following an aggressive multimodal immunotherapy regimen of corticosteroid pulses, Intravenous Immunoglobulin (IVIG), and rituximab, the patient achieved significant recovery of cardiac, renal, and neurological functions. CONCLUSIONS: This case demonstrates that SLE can present as a life-threatening "autoimmune storm" mimicking sepsis or primary heart failure. Early identification is vital in atypical critical illness, as aggressive immunotherapy can reverse even severe multiorgan dysfunction. Clinicians should consider autoimmune screening in cases of unexplained cardiac arrest and multiorgan failure to prevent diagnostic delays and improve outcomes.