Rituximab therapy for myopathy associated with anti–signal recognition particle antibodies: A case series

Objective

The myopathy associated with anti–signal recognition particle (anti‐SRP) is a severe necrotizing immune‐mediated disease characterized by rapidly progressive proximal muscle weakness, markedly elevated serum creatine kinase (CK) levels, and poor responsiveness to traditional immunosuppressive therapies. Reports on the efficacy of B cell depletion therapy for anti‐SRP–associated myopathy are mixed. We describe 8 patients with anti‐SRP–associated myopathy and their response to treatment with the anti‐CD20 monoclonal antibody rituximab.

Methods

We identified 8 patients with myopathy who tested positive for anti‐SRP antibodies by immunoprecipitation and were treated with rituximab as part of clinical care. We reviewed their medical records to assess clinical, serologic, and histologic characteristics and response to therapy. In 5 patients, serum was collected before and after rituximab therapy. Autoantibodies were detected by immunoprecipitation and quantitated by densitometry, and the percent decreases in anti‐SRP autoantibody levels were calculated.

Results

Six of 8 patients who had been refractory to standard immunosuppressive therapy demonstrated improved manual muscle strength and/or decline in CK levels as early as 2 months after rituximab treatment. Three patients sustained the response for 12–18 months after initial dosing. All of the patients were continued on adjunctive corticosteroids, but doses were substantially reduced after rituximab. Quantitative levels of serum anti‐SRP antibodies also decreased after rituximab treatment.

Conclusion

B cell depletion therapy with rituximab is effective for patients with myopathy associated with anti‐SRP. The substantial decrease in anti‐SRP antibody levels after rituximab treatment also suggests that B cells and anti‐SRP antibodies may play a role in the pathogenesis of this myopathy.     

抗信号识别颗粒抗体阳性肌病伴心脏损害1例

1临床资料患者,男,43岁,因四肢近端肌肉无力9个月,加剧1周于2013年9月22日入院。患者于9个月前无明显诱因下出现四肢肌肉无力,以近端肌力减退为主,主要表现为上楼梯费力,提重物困难,易疲劳,尚可参加工作,无发热、皮疹、肌痛、感觉异常等,无明显晨轻暮重的波动现象,上述症状逐渐加重,劳动耐量和日常生活能力进行性下