Libman-Sacks Endocarditis as the Initial Presentation of Systemic Lupus Erythematosus and Antiphospholipid Syndrome: A Multisystem Diagnostic Challenge.

Libman-Sacks endocarditis (LSE), characterized by sterile valvular vegetations, is a recognized complication of systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). However, its occurrence as the initial manifestation of previously undiagnosed autoimmune disease is uncommon and may create significant diagnostic uncertainty. A 27-year-old female presented to the emergency department with acute-onset exertional dyspnea, cough, and severe anemia, with a history of three consecutive first-trimester miscarriages. Initial evaluation revealed severe mitral regurgitation with valvular masses, raising suspicion for infective endocarditis. Further workup demonstrated elevated inflammatory markers, autoimmune hemolytic anemia, nephrotic-range proteinuria, and positive autoimmune serology, including antinuclear antibodies, anti-double-stranded DNA, anticardiolipin IgG, anti-β2-glycoprotein I IgG, and lupus anticoagulant. Transthoracic echocardiography showed severe mitral regurgitation with valvular masses and reduced left ventricular ejection fraction, while transesophageal echocardiography confirmed Libman-Sacks vegetations. Computed tomography of the chest revealed diffuse alveolar hemorrhage. The patient was diagnosed with new-onset SLE and APS, presenting with LSE and multisystem involvement. Management included pulse methylprednisolone therapy, hydroxychloroquine, cyclophosphamide, therapeutic anticoagulation, and plasma exchange for alveolar hemorrhage, resulting in clinical improvement with resolution of hemoptysis and improvement in cardiac function. This case is particularly notable because severe valvular disease led to the initial recognition of previously undiagnosed SLE and APS in the setting of simultaneous pulmonary, hematologic, renal, and obstetric manifestations. It highlights the importance of considering autoimmune etiologies in young patients with unexplained valvular heart disease, particularly in the presence of suggestive systemic features.