New-Onset Systemic Lupus Erythematosus Complicated by Preeclampsia, HELLP Syndrome, and Lupus Nephritis During a Third-Trimester Pregnancy: A Case Report.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that primarily affects women of reproductive age. Most patients are diagnosed prior to conception; however, new-onset SLE during pregnancy is rare and can mimic common obstetric complications, delaying diagnosis and treatment. Such overlap increases the risk of maternal morbidity and adverse pregnancy outcomes (APOs). A primigravida adolescent in her third trimester presented with severe preeclampsia, HELLP syndrome, and nephrotic-range proteinuria. Postpartum, she developed hemorrhage requiring a modified B-Lynch suture in the ICU, along with vulvar edema, discoid skin lesions, joint pain, and photosensitivity. Laboratory evaluation revealed positive antinuclear antibodies, anti-double-stranded DNA antibodies, hypocomplementemia (characterized by low levels of C3 and C4), and proteinuria, confirming the diagnosis of new-onset SLE with lupus nephritis. The clinical course was managed with corticosteroids, hydroxychloroquine, and supportive therapy. This case highlights the diagnostic complexity of autoimmune disease in pregnancy, particularly when clinical manifestations overlap with obstetric emergencies such as HELLP syndrome and preeclampsia. It underscores the need for early consideration of SLE in atypical or multisystem presentations, prompt biomarker testing, and timely initiation of immunosuppressive therapy. Management in a specialized center, with a multidisciplinary team, is essential to optimizing maternal and neonatal outcomes.