Description Neonatal lupus was developed in infants born from mother with autoimmune disorders through transplacental autoimmune antibodies. Macrophage activation syndrome (MAS) occur in autoimmune diseases and is fatal complication that led to death if not promptly diagnosed and treated appropriately. MAS in neonatal lupus is very rare.

A 33 days-old female was admitted due to fever with pancytopenia. Her skin was showed multiple erythema marginatum like rash on whole body. She was born from primipara mother without any autoimmune disorders. She was admitted at another hospital due to skin rash at post-natal 5 days and diagnosed with neonatal lupus because her mother auto immune study had positive anti-nuclear antibody (ANA) and anti-SSA (+), SSB (+). On admission, laboratory data were shown as 5.6 g/dL hemoglobin, 1,100/μL white blood cells (absolute neutrophil count: 110/μL), and 71,000/μL platelet. Inflammatory biomarkers showed C-reactive protein was 9.17mg/dL, and procalcitonin 1.88 ng/mL, and ferritin 1,507 ng/mL. DIC profiles were showed that INR of prothrombin time was over 5, aPTT over 120 seconds, and antithrombin III 64.2%, fibrinogen 401 mg/dL. We began empirical antibiotics for septicemia and high dose methylprednisolone (mPD) therapy for MAS. She received supportive care with packed red cell transfusion, fresh frozen plasma, and anti-thrombin. Body temperature decreased 3 days later after mPD treatment, and we changed to oral dexamethasone. We got results for decreased NK cell activity and high-level of soluble IL-2 (5,187 U/ml). Her auto-immune study showed ANA (1:320), anti-SSA (+3), and anti-SSB (+3). She was diagnosed with MAS in neonatal lupus. Her condition and laboratory data were recovered and discharged. Her clinical findings and auto-antibodies were disappeared at 9 month-of age.

Conclusions Our case suggested that we should consider neonatal lupus if there was neonatal fever and erythematous rash in infants born to mother even without autoimmune history.