Hemophagocytic Lymphohistiocytosis Thought to Be due to Undifferentiated Connective Tissue Disease Treated With Ruxolitinib: A Case Report.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, systemic inflammatory syndrome. Cases without an identifiable acquired trigger are referred to as secondary HLH. In this report, we describe the case of a 24 year-old woman whose underlying cause of HLH was particularly difficult to determine. Her condition was initially suspected to be due to lamotrigine use but is now thought to be a result of undifferentiated connective tissue disease. During the patient's prolonged and complex hospital stay, she received the diagnosis of secondary HLH. Discontinuing lamotrigine, a drug that rarely causes HLH, did not improve her condition. The patient was tested for infectious and malignant conditions with negative results. Further workup revealed a positive ANA and bilateral MCP tenosynovitis, with negative specific antibodies, suggesting an undefined rheumatologic process. A number of conventional therapies did not show clear benefit, including etoposide, high-dose steroids, rituximab, and plasmapheresis. The patient remained in critical condition until she began treatment with ruxolitinib, with which she remains stable more than 5 years later. Ruxolitinib has shown some success in treating HLH in preliminary studies, but it is still considered a salvage therapy. This case illustrates the successful use of ruxolitinib in a patient with HLH likely due to undifferentiated connective tissue disease.