Background/Purpose:  The use of Rituximab (RTX) in patients with autoimmune diseases has been associated with an increased incidence of infection and risk factors for this complication are not well established. The aim of our study was to compare the incidence of infections and its related factors in the first six months after RTX infusion in two rheumatic diseases: systemic lupus erythematosus (SLE) and inflammatory myopathies (IM).

Methods: From August 2009 to March 2015, a total of 48 SLE and 39 IM consecutive patients were longitudinally followed in the biologic therapy center of Rheumatology Division of a tertiary university hospital using a standardized electronic database protocol including demographic data, clinical and laboratorial findings and treatment. RTX is regularly administered in our center with infectious screening and the protocol consisted of either 4 weekly doses of 375mg/m² or two doses of 1g (day 0 and 14). IM standard treatment also included the recommendation of IVIG 2-4 weeks pre RTX infusion, whereas IVIG was only indicated for lupus for severe refractory activity. Severe infection was defined as episode that required the use of intravenous antibiotics or hospitalization.

Results:  SLE patients presented a significant higher incidence of overall (50.0 vs. 7.7%, p<0.001) and severe (22.9 vs. 0%, p<0.001) infections than IM patients in the first 6 months after RTX infusion. SLE and IM patients had similar age (38.0±13.3 vs. 41.5±13.2, p=0.230) and frequency of female gender (93.8 vs. 82.1%, p=0.105). At baseline, both groups had similar mean IgG level (1168.8±527.0 vs. 1346.3±397.0 mg/dL, p=0.087). With regard to treatment, mean prednisone dose (32.0±21.1 vs. 22.3±15.4mg/day, p= 0.018) was higher in SLE but the frequency of patients with associated immunosuppressants was lower in SLE (79.2 vs. 97.4%, p=0.020). IVIG infusion (2g/Kg) before RTX infusion was less often used in SLE than in IM patients (14.6 vs.69.2%, P<0.001). Previous history of severe infection 6 months before RTX was alike in SLE and IM (10.4 vs. 2.6%, p=0.218). Further analysis of 11 severe infection episodes revealed that they only occurred in SLE, more than half (64%) were sepsis and they were observed at a mean of 3.6 months (range 1 – 5 months) post infusion. At baseline, these patients were under a mean prednisone dose of 41.4±30.2mg/day and their mean IgG level was 1361.5±753.1 mg/dL.

Conclusion:  We observed that SLE was associated with an unexpected higher incidence of overall and severe infections than IM patients in spite of adequate and comparable baseline IgG levels. Risk factors identified were high glucocorticoid dose and less use of pre-RTX IVIG infusion. Further studies are necessary to determine if the recommendation of IVIG pre-RTX treatment will reduce severe early infection in SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-factors-for-severe-infections-in-rituximab-treated-patients-comparison-of-systemic-lupus-erythematosus-and-inflammatory-myositis/