Anti-signal recognition particle autoantibodies: marker of a necrotising myopathy

Abstract

OBJECTIVE: To elucidate the clinical importance of the anti-signal recognition particle (SRP) autoantibody in patients with myositis.\ud METHODS: Retrospective systematic assessment of the clinical, laboratory and histological characteristics of 23 anti-SRP-positive patients from six European centres. Data were compared with a large group of anti-SRP-negative patients with myositis published previously.\ud RESULTS: Clinically, patients with anti-SRP autoantibodies often had a severe symmetric proximal muscle weakness resulting in marked disability, dysphagia and highly elevated levels of serum creatine kinase. Three patients had typical dermatomyositis rashes. The disease was associated with the occurrence of extramuscular signs and symptoms including interstitial lung disease. No association was found with an increased risk of cardiac involvement, and the disease carried a reasonably favourable prognosis with most patients responding to treatment. None of the patients had the typical histological features of myositis. Most muscle biopsy specimens showed the presence of necrotic muscle fibres and no inflammatory infiltrates.\ud CONCLUSIONS: Anti-SRP autoantibodies are associated with a syndrome of a necrotising myopathy in the spectrum of immune-mediated myopathies that differs from typical polymyositis. Further studies are needed to elucidate the pathogenesis and to clarify the role of the anti-SRP autoantibodies in this unique diseas

Signal recognition particle (SRP) positive myositis in a patient with cryptogenic organizing pneumonia (COP)

“…Interstitial lung disease may be found in one quarter of patients suVering from anti-SRP autoimmune myositis, not diVering in incidence from polymyositis or dermatomyositis [5,9,11,16]. In our patient, cryptogenic organizing pneumonia occurred about one and a half years prior to the emergence of myositis, although anti-SRP antibodies were present from the very beginning.…”

“…This case is unusual, as myositis showed full regression without oral immune suppression but with extracorporeal treatment, performed as a combined therapy of plasmaexchange and immunoadsorption, which is said to be of little to no use in treating myositis [5,[9][10][11][12]. However, plasmaapheresis is already done for almost 3 years and is still continued without any side eVects.…”

“…However, plasmaapheresis is already done for almost 3 years and is still continued without any side eVects. According to Hengstman et al [9,13], treatment for myositis may be done for years.…”

“…In our patient, cryptogenic organizing pneumonia occurred about one and a half years prior to the emergence of myositis, although anti-SRP antibodies were present from the very beginning. Although, we can only speculate if SPR-autoantibodies have induced cryptogenic organizing pneumonia, literature reports interstitial lung disease in about one-third of cases preceeding autoimmune myositis [5,9,17]. According to Tazelaar [18], polymyositis or dermatomyositis may be accompanied by either usual interstitial pneumonia (UIP), diVuse alveolar damage (DAD) or bronchiolitis obliterans organizing pneumonia (BOOP, now called COP).…”

“…DiVuse alveolar damage is reported to have the worst prognosis and bronchiolitis obliterans organizing pneumonia (BOOP/COP) has the most favorable prognosis [10,15,19]. Anti-SRP antibodies, which are mainly polymyositis speciWc, may also be found in dermatomyositis or systemic sclerosis [5,9,13]. In a recent report, Suzuki et al [20] suggest to classify SRP positive myositis as a particular form of polymyositis.…”