Background/Purpose: A multinational collaborative effort aimed to develop a new set of criteria for macrophage activation syndrome (MAS) complicating systemic juvenile idiopathic arthritis (sJIA) has been recently started. The first step of the project, based on a Delphi survey, has been completed (Davì S et al. J Rheumatol 2011;38:764-8). The second step, whose goal is to collect the data of a sizable sample of children with MAS and with potentially ‘confusable’ conditions, is currently under way. The study aim is to describe the demographic, clinical, laboratory, histopathologic, therapeutic and prognostic features of children with MAS collected so far in the data-collection phase of the project.

Methods: Investigators who participated in the Delphi survey were asked to enter the information of their patients with MAS collected retrospectively in a web-based database, developed by the Pediatric Rheumatology International Trials Organization (PRINTO).

Results: At the 31^st of May, 2012, 312 patients with sJIA-associated MAS have been entered in the study website by 87 investigators from 27 countries. 181 (58%) patients were females and 131 (42%) were males. The age at onset of sJIA ranged from 0.2 to 15,9 years (median 5,1 years) and the disease duration from onset of sJIA and onset of MAS ranged from 0 to 15,6 years (median 0,3 years). MAS occurred at onset of sJIA in 50 (20,2 %) patients. The frequency of the clinical, laboratory and histopathologic features of MAS is reported in the Table. The most frequently reported trigger of MAS was active disease (35,3%), followed by infection (26,3%) and medication toxicity (3,7%). 69 (37,1%) patients were admitted in the ICU. Therapeutic interventions included iv steroids (88.0%), oral steroids (74.1%), cyclosporine (65.5%), other immunosuppressants (13.8%), iv Ig (36.3%), etoposide (11.1%), anakinra (6.8%), and plasma exchange (5.4%). The mortality rate was 8.2%.

Table. Frequency of clinical, laboratory, histopathologic features of 312 patients with MAS.

Feature	No. with info available	Percentage
Falling platelet count (≤ 262 x10^9/l)	286	74.8
Hyperferritinemia (≥ 500 ng/ml)	256	91.4
Bone marrow hemophagocytosis	214	60.7
Increased liver enzymes (AST > 59UI/L)	275	74.9
Falling leukocyte count (< 4x10^9/l)	285	21.1
Persistent continuous fever ≥ 38°C	302	63.9
Hypofibrinogenemia (≤ 2,5 g/l)	250	48.4
Hypertrigliceridemia (≥ 265 mg/dl)	221	43.9
Central nervous system dysfunction	302	36.1
Increased D-dimer (≥ 500 ng/ml)	105	88.6
Hemorrhagic manifestations	301	20.9
Liver enlargement	305	70.5
Spleen enlargement	301	59.5

Conclusion: Hyperferritinemia, increased liver enzymes and falling platelet count were the most frequently observed laboratory abnormalities.The frequency of falling leukocyte count was unexpectedly low. Also unexpectedly, liver and spleen enlargement were recorded more frequently than persistent continuous fever. Hemophagocytosis was noticed in around two third of patients who underwent bone marrow aspirate. As expected, corticosteroids and cyclosporine were the most commonly administered medications.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-and-therapeutic-features-of-312-patients-with-macrophage-activation-syndrome-enrolled-in-a-multinational-survey/