Atypical presentation of macrophage activation syndrome with extreme D-dimer elevation in juvenile systemic lupus erythematosus

Macrophage Activation Syndrome (MAS) is a potentially life-threatening complication of juvenile systemic lupus erythematosus (jSLE), an uncommon but severe autoimmune disease in children. This case report presents a 7-year-old child newly diagnosed with jSLE who developed MAS, marked by persistent fever, abdominal pain, rash, cytopenia, elevated ferritin, hypertriglyceridemia, hypofibrinogenemia, and significantly elevated D-dimer levels. Diagnostic evaluation revealed low complement levels, positive antinuclear antibodies (ANA), and anti-double-stranded DNA (anti-dsDNA), confirming jSLE based on the SLICC classification criteria and MAS according to the EULAR/ACR criteria. Intensive therapy, including methylprednisolone, intravenous immunoglobulin, hydroxychloroquine, and anakinra, led to clinical improvement. This case underscores the unique occurrence of MAS in a patient at the initial diagnosis of jSLE, with an exceptionally elevated D-dimer. Clinicians should maintain a high level of vigilance for MAS in pediatric jSLE cases presenting with systemic inflammation and hematologic abnormalities, as prompt recognition and intervention are essential to improve outcomes.