Adult-Onset Still's Disease Presenting as Macrophage-Activation Syndrome With Critical Illness in the Third Trimester of Pregnancy: A Case Report

BACKGROUND: We report a case of a young woman with adult-onset Still's disease presenting as macrophage-activation syndrome complicated by shock and respiratory failure during the third trimester of pregnancy. CASE SUMMARY: A previously healthy 26-year-old woman at 35 weeks of gestation presented with 1 week of constitutional symptoms and was found to be febrile, tachycardic, and hypotensive. She delivered a healthy neonate by cesarean section. Following delivery, she had worsening hypotension and fevers despite fluid resuscitation and antibiotics, and developed progressive hypoxemia requiring up to 60% Fio₂, with bilateral upper-lobe predominant opacities on chest CT. She also had laboratory derangements including anemia, thrombocytopenia, low fibrinogen, elevated ferritin, and abnormal liver chemistries. After extensive testing to exclude infections, hemolysis, and other pertinent disorders, the development of polyarthralgias and a characteristic rash fulfilled criteria for adult-onset Still's disease complicated by macrophage-activation syndrome. Her condition improved with immunosuppressive therapy. CONCLUSION: To our knowledge, this is the first report of new-onset adult-onset Still's disease during the third trimester of pregnancy, which presented as macrophage-activation syndrome. In the context of late pregnancy, macrophage-activation syndrome can mimic or raise concern for hemolysis, elevated liver enzymes, and low platelet syndrome and other peripartum disorders. Furthermore, the characteristic articular symptoms of adult-onset Still's disease may be mild and/or delayed, and pulmonary involvement with severe hypoxemia can occur. Clinicians should consider this diagnosis when evaluating a pregnant patient with unexplained fever and multiorgan dysfunction.