Macrophage Activation Syndrome/Secondary Hemophagocytic Lymphohistiocytosis in Adult‐Onset Still's Disease: An Uncommon Initial Presentation in a Young Nepalese Female: A Case Report

Hemophagocytic lymphohistiocytosis (HLH), is a fatal systemic hyperinflammatory syndrome. HLH may be due to immunosuppression, infections, cancer, or autoimmune diseases with fever and cytopenia. HLH which occurs in adult-onset Stills disease (AOSD) is called secondary HLH, also known as macrophage activation syndrome (MAS). Here, we present a case of a 36-year-old Nepalese female, with no known comorbidities presented with a history of fever, sore throat, multiple joint pain, fluctuating rash, hair loss, and unintentional weight loss for a month. She was hypotensive, with a high-grade fever. She had swollen eyelids, and erythematous macular rashes in the face, trunk, and extremities with the rest of the systemic examinations normal. Investigation showed leukocytosis, with anemia, and a blood smear showed neutrophilic leukocytosis. ESR/CRP and lactate dehydrogenase (LDH) were elevated, and ferritin was 38,291 ng/mL. Tropical disease screening, blood culture, viral serologies, imaging for malignancies, and autoimmune disease panels were negative. She met the diagnostic criteria for AOSD. MAS was suspected of abnormally high ferritin levels, and a bone marrow aspiration biopsy was done. She was given IV steroids with some improvement. The biopsy showed hypercellular marrow with erythroid hyperplasia, dyserythropoietic changes, and increased macrophages with phagocytic activity suggestive of MAS. She was started on dexamethasone and cyclosporine which eventually improved her condition. Several complications can arise in AOSD, around 15% of these patients can have MAS which is regarded as one of the most severe complications. With studies showing a mortality rate of more than 50% in patients of AOSD with MAS which is five times more than the mortality rate with AOSD alone, understanding this combined picture and timely aggressive treatment has a huge importance.