Hemophagocytic lymphohistiocytosis (HLH) is a rare and severe pathological condition caused by an abnormal and excessive immune response. It is usually caused by an underlying stimulus, most often an infection. HLH clinical manifestations include persistent fever, cytopenia, hepatosplenomegaly, and increased levels of condition-specific biomarkers. Patients may also experience coagulopathy, liver dysfunction, damage to the central nervous system, multi-organ failure, and other associated symptoms. A significant proportion of patients with HLH have underlying genetic disorders that predispose them to the syndrome. HLH can also occur in patients with rheumatologic or auto- inflammatory disorders, in which case it is known as macrophage activation syndrome (MAS). Juvenile systemic arthritis, adult-onset Still’s disease, and systemic lupus erythematosus are the most common conditions associated with MAS. HLH primarily affects infants between the ages of birth and 18 months, but it can occur at any age. The diagnosis of HLH is frequently difficult due to the condition’s rarity and the lack of knowledge surrounding it, resulting in a delay in diagnosis.
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