Background/Purpose

Macrophage activations syndrome (MAS) occurring in the context of systemic juvenile idiopathic arthritis (sJIA) can pursue a rapidly fatal course. However, the diagnosis of the syndrome is often challenging as its features may be mimicked by those of confusable conditions, such as flares of the underlying disease or systemic infections. In addition, the clinical spectrum of MAS is known to be heterogeneous. The aim of this study is to seek insights into the heterogeneity of MAS by comparing the characteristics of patients enrolled in a large multinational survey in relation to geographic origin of patients, specialty of attending physician, demonstration of hemophagocytosis (HP), and outcome. 

Methods Patient data were collected retrospectively by pediatric rheumatologists (PR) or pediatric hemato-oncologists (PHO) and entered in a web-based database. Clinical and laboratory features, therapeutic interventions and outcome were compared between subgroups by means of Mann-Whitney U test or chi-square/Fisher exact test, as appropriate. “Severe course” was defined as the occurrence of ICU admission or death. 

Results A total of 362 patients with sJIA-associated MAS were collected by 95 investigators from 33 countries. 179 patients (49.4%) were enrolled in Europe (EU), 72 (19.9%) in North America (NA) and 111 (30.7%) in other continents (OC). 283 (88.2%) patients were included by PR and 79 (21.8%) patients by PHO. Bone marrow HP was detected in 160 (44.2%) patients and was not detected or looked for in 202 (55.8%) patients. Severe course was reported in 92 (25.4%) patients. Comparison by geographic origin showed a lower frequency of CNS disease and higher levels of liver transaminases in EU patients. NA physicians used more frequently iv Ig and biologics than did physicians from EU and OC. Patients entered by PHO had a greater frequency of multiorgan failure and were given more commonly biologics and etoposide, whereas patients seen by PR received more frequently cyclosporine.  Patients with demonstration of HP had shorter duration of sJIA at MAS onset, higher prevalence of hepatosplenomegaly, lower levels of platelets and fibrinogen and higher levels of triglycerides, and were given more frequently cyclosporine, iv Ig and etoposide. Patients with severe course were older, had a longer duration of sJIA at MAS onset and had a greater frequency of haemorrhages and CNS dysfunction, lower levels of ESR, albumin and fibrinogen, higher levels of LDH, triglycerides and D-dimer, and were treated more commonly with cyclosporine, iv Ig and etoposide. 

Conclusion Clinical, laboratory and histopathologic features of sJIA-associated MAS were overall comparable among patients from different continents, whereas there was a disparity in the therapeutic choices made by specialists practicing in different geographic areas or fields. Patients with demonstration of HP or severe course presented with a more acute clinical and laboratory picture and were treated more aggressively.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dissecting-the-heterogeneity-of-macrophage-activation-syndrome/