Case reportMarked efficacy of a therapeutic strategy associating prednisone and plasma exchange followed by rituximab in two patients with refractory myopathy associated with antibodies to the signal recognition particle (SRP)
Introduction
Antibodies to the signal recognition particle (SRP) are detected in 5–6% of patients with idiopathic inflammatory myopathy [1], [2]. Patients with anti-SRP antibodies usually develop severe myopathy with high serum creatine kinase (CK) levels, specific pathological features upon muscle biopsy and usually poor response to corticosteroids (CS) [3], [4]. We here report on the marked efficacy of a combination therapy of corticosteroids (CS) and plasma exchange (PE) followed with rituximab in two patients with severe intractable myopathy associated with anti-SRP Abs.
Section snippets
Case 1
A 20-year-old Malian man presented in 1988 with myalgia, proximal limb weakness and high serum CK. The diagnosis of myositis was made upon muscle biopsy. He had a past history of urinary bilharziosis and hepatitis B and delta viruses co-infection responsible for chronic hepatitis.
He successively received CS, intravenous immunoglobulins (IVIg), CS and PE, cyclosporine A (CyA), intravenous pulse cyclophosphamide (CYC), and mycophenolate mofetil. However, only CyA and the combination of CS and PE
Case 2
A 24-year-old woman from Senegal presented in December 1999 with severe symmetrical proximal weakness, graded at 2/5–3/5 in proximal arms and legs and 1/5 in the neck flexor. Serum CK was high at 10,000 IU/l. Serum anti-nuclear Abs were positive (1:1280), with a cytoplasmic fluorescence. Anti-SRP Abs were identified by immunoblotting. Anti-synthetase Abs were negative. A muscle biopsy revealed many necrotic and regenerating fibres, a single focus of mononuclear cells in the endomysium and MHC
Discussion
Our two patients had typical ‘anti-SRP syndrome’ with severe myopathy, high serum CK, muscle fiber necrosis and regeneration, prominent endomysial fibrosis, little or no inflammation upon muscle biopsy and poor response to conventional treatment [3].
There are several lines of argument for the humoral immune mediated nature of the ‘anti-SRP syndrome’: (i) there is no argument for a CD8+T cell mediated cytotoxicity, since there is a lack of myofiber major histocompatibility complex (MHC) class 1
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