Background/Purpose: Macrophage activation syndrome (MAS) is a life-threatening inflammatory complication of childhood-onset systemic lupus erythematosus (cSLE). There are few reports of long-term outcomes of MAS complicating cSLE. Our aim is to compare long-term outcomes between MAS and non-MAS patients with cSLE seen at a single tertiary centre.

Methods: Our retrospective review included all patients followed at the Hospital for Sick Children, Toronto, diagnosed with cSLE (≥ 4/11 ACR classification criteria and/or ≥ 4/11 SLICC classification criteria) between January 2002 and December 2012. Within this cohort we identified cSLE patients also diagnosed with MAS (as per Pediatric Rheumatologist’s expert opinion). We analyzed prospectively collected data including: 1) demographics: gender, age of diagnoses; 2) SLE major organ involvement (proliferative and membranous lupus nephritis and CNS involvement); 3) immunosuppressive drugs; 4) average daily dose of corticosteroids and 5) SLICC damage index at last visit. Continuous variables were compared using Student’s t test and categorical variables were compared using Fisher’s test as appropriate. 

Results: 402 patients with cSLE were identified. Of those, 34 (8.4 %) patients were also diagnosed with MAS. The majority (76%) of patients with MAS developed it concomitantly with their SLE diagnosis. There was no statistically significant difference in the proportion of patients with major organ involvement between MAS and non-MAS patients (Table). A larger proportion of MAS patients received calcineurin inhibitors and IVIG as compared with non-MAS patients (p <0.01). Azathioprine was used more frequently in non-MAS patients than in patients with MAS (p = 0.01). There was no difference in the average daily dose of steroids, frequency of cyclophosphamide or biologic therapy use throughout follow-up. The proportion of patients who sustained damage (SLICC ≥ 1) at last visit was similar between the groups.

Conclusion: We observed that MAS was most likely to be diagnosed concomitantly with cSLE diagnosis. Despite the life-threatening nature of MAS complicating cSLE, we observed comparable rates of major organ involvement, average dose of steroids, use of cytotoxic drugs and disease associated damage between those cSLE patients with MAS and those non-MAS patients throughout their follow-up. As expected, calcineurin inhibitors and IVIG were more commonly used among those with MAS. 

Table. Characteristics of MAS and non-MAS cSLE patients.

1. Nonsteroidal medication validated in 29 MAS and 240 non-MAS patients; 2. Mycophenolate mofetil; 3. Tacrolimus or Cyclosporine; 4. Intravenous immunoglobulin; 5. Steroids reported as mg/day of prednisone equivalents; 6. SLICC scores at final visit validated in 32 MAS and 297 non-MAS patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/long-term-outcomes-of-macrophage-activation-syndrome-in-childhood-onset-systemic-lupus-erythematosus/