Fact 12: The Overlap Between HLH and Macrophage Activation Syndrome (MAS)
Macrophage Activation Syndrome (MAS) is considered a subset of HLH. Like HLH, MAS is characterized by an overactive immune response leading to excessive inflammation. However, MAS is typically associated with rheumatic diseases, particularly systemic juvenile idiopathic arthritis (sJIA).
Both HLH and MAS share several common features, including fever, splenomegaly, cytopenias, and high levels of certain blood markers such as ferritin. They also share similar treatment approaches, which aim to suppress the overactive immune response and manage the resulting symptoms.
Despite the similarities, there are some key differences between HLH and MAS. One major difference lies in the triggering factors. While genetic mutations play a significant role in primary HLH, MAS is typically triggered by an underlying rheumatic disease. The severity and progression of the conditions can also differ, with MAS often presenting as a more acute, rapidly progressive disease.
The overlap of symptoms between HLH and MAS can pose a significant diagnostic challenge. It’s essential to differentiate between the two conditions, as they may require different treatment strategies depending on the patient’s overall health and the severity of their symptoms.(12)
