Hemophagocytic Lymphohistiocytosis for the Inpatient Dermatologist

Hemophagocytic lymphohistiocytosis (HLH) is a potentially life-threatening condition characterized by dysregulation of the immune system leading to overproduction of inflammatory cytokines. HLH is categorized as primary or secondary based on presence of genetic mutations or other triggers such as malignancy, infection, or autoimmune conditions. This review aims to explore pathogenesis and cutaneous manifestations of HLH, which may be relevant for dermatologists practicing in a hospital-based setting as the morphology and distribution of cutaneous findings in HLH have not been well documented in the literature. An overview of skin findings seen in primary and secondary HLH are outlined in Table  3. Pertinent differential diagnoses to consider are also discussed, including but not limited to macrophage activating syndrome (MAS) and adult-onset Still disease (AOSD). HLH can present similarly to sepsis, so a high index of clinical suspicion is needed to diagnose the condition. While HLH is rare, morbidity and mortality are high; therefore, treatment should be started promptly following diagnosis.