Cytoplasmic T Lymphocyte Antigen-4 (CTLA-4) gene encodes for a glycoprotein, expressed on activated T-cells to transfer an inhibitory signal to control T-cell activation and proliferation. Techniques coupled with Real-time Polymerase Chain Reaction (PCR) and High-Resolution Melting Analysis (HRMA) were used to screen a missense signal peptide polymorphism (CTLA-4 + 49 A/G rs231775) in the Indian population to detect its association with Rheumatoid Arthritis (RA). Further, the resulting outcome was confirmed by Sanger\'s sequencing technique, and genotype frequencies were calculated. In eukaryotic cells, the M domain of the Signal Recognition Particle (SRP-54) recognizes the N-terminal region of the Signal Peptide (SP) sequence. It directs the polypeptide chain into the Sec-61 translocon of the Endoplasmic Reticulum (ER) for further protein modification. As the Single Nucleotide Polymorphism (SNP) rs231775 lies in the signal peptide region of CTLA-4, an in-silico study was also performed to predict the mRNA stability and SP-SRP protein interaction. From the study, it was observed that the genotype frequency of rs231775 SNP G/G homozygous dominant was significantly higher in RA patients than G/A heterozygous dominant and A/A homozygous recessive conditions (Odd Ratio (OR) = 2.0862; 95 % Confidence Interval (C.I) = 1.2584 to 3.4584; Relative Risk (RR) = 1.8507; P = 0.0044). Moreover, the rs231775 SNP G allele frequency was higher than the control group G = 0.407 (40.7 %) vs 0.32 (32 %). In silico approaches of Protein-Protein docking and Molecular Dynamics (MD) simulation reveal CTLA-4 rs231775 SNP (G allele) has destabilized the SP-SRP protein complex, which may affect the translocation of CTLA-4 nascent polypeptide chains into the ER via activating Regulation of Aberrant Protein Production (RAPP) pathway.

Immune-mediated necrotizing myopathy (IMNM) is a rare subtype of idiopathic inflammatory myopathy that is characterized by severe subacute proximal weakness, myofiber necrosis, and significantly elevated serum creatine kinase. Anti-signal recognition particle (SRP) and anti-3-hydroxy-3-methylglutaryl-coenzyme-A reductase autoantibodies have been found in about two-thirds of patients with IMNM. This myopathy is usually idiopathic and there is a scarce literature concerning its association with connective tissue diseases. Herein, we report an unusual case of a young woman who presented with both rheumatoid arthritis and severe anti-SRP IMNM. Thankfully to a therapeutic protocol combining rituximab and cyclophosphamide, an important improvement was achieved, and notably no serious side effect was observed.

Immune-mediated necrotizing myopathies (IMNM) is a rare disease that was first described in 2004. Due to the lack of large case series, there are no formal treatment recommendations for IMNM.
We presented a case of a 47-year-old woman who experienced progressive limb weakness, starting from the lower limbs and gradually affecting the upper limbs. She also reported experiencing dyspnea after engaging in daily activities. When she was admitted to the hospital, her upper limbs were almost unable to move and she could not stand even with support. Her Creatine kinase (CK) level significantly increased (> 3500 u/l). Electromyography showed myogenic damage, anti-Signal recognition particle (anti-SRP) and anti-Ro52 antibodies were highly positive. Pathological biopsy of the right biceps muscle showed necrotizing myopathy in the skeletal muscle. She was ultimately diagnosed with anti-SRP IMNN, and was given monotherapy with methylprednisolone and combination therapy with immunoglobulin, but her symptoms continued to worsen. The patient refused to bear the possible further liver dysfunction and blood system damage caused by Cyclophosphamide and Rituximab, and she chose to try to use Ofatumumab (OFA).
After receiving three doses of OFA treatment without any adverse reactions, she reported that her muscle strength had basically recovered and she was able to walk independently. The B cells in the circulatory system have been depleted, and blood markers such as liver function have consistently remained within normal range. During the follow up, her activity tolerance continued to improve.
We have presented a severe case of SRP-IMNM in which the patient showed poor response to conventional immunotherapy. However, rapid symptom relief was achieved with early sequential use of OFA treatment. This provides a new option for the treatment of SRP-IMNM, and more large-scale studies will be needed in the future to verify our results.

Autosomal dominant mutations in the signal recognition particle (SRP) 54 gene were recently described in patients with severe congenital neutropenia (SCN). SRP54 deficiency cause a chronic and profound neutropenia with maturation arrest at the promyelocyte stage, occurring in the first months of life. Nearly all reported patients with SRP54 mutations had neutropenia without a cyclic pattern and showed a poor or no response to granulocyte colony-stimulating factor (G-CSF) therapy. We report here an 11-year-old female patient with cyclic neutropenia and recurrent heterozygous p.T117del (c.349_351del) in-frame deletion mutation in SRP54, who showed remarkable therapeutic response to G-CSF treatment. The diagnosis of cyclic pattern of neutropenia was established by acceptable standards. ELANE gene mutation was excluded by using various genetic approaches. The patient described here also had dolichocolon which has not been described before in association with SCN.

We have reported a case of a 44-year-old woman with anti-signal recognition particle (SRP) antibody-positive immune-mediated necrotizing myopathy triggered by human parvovirus B19 (PVB19) infection. She was admitted to the hospital because of lower leg edema and muscle weakness after erythema infectiosum. Magnetic resonance imaging of the lower extremities revealed high signals in the proximal muscles and subcutaneous edema on STIR. Muscle biopsy showed myofiber regenerative changes and variation in fiber size. A myositis-specific autoantibody profile indicated a positive result for anti-SRP antibodies. We diagnosed the patient with immune-mediated necrotizing myopathy (IMNM). Muscle strength and subcutaneous edema improved gradually in 3 months following immunotherapy. This is the first case report of an IMNM associated with PVB19 infection.

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Immune-mediated necrotizing myopathy (IMNM) is characterized by proximal limb weakness, elevated creatine kinase (CK) levels, and myofiber necrosis without or with only a small amount of inflammatory cell infiltrate. There is only 1 report of hypothyroidism combined with antibody-negative IMNM to date. We aimed to describe a rare case of hypothyroidism combined with anti-signal recognition particle (SRP) IMNM for the first time and review the previous literature. A 50-year-old male, who had a 4-year history of hypothyroidism treated with levothyroxine replacement therapy, presented with progressive symmetrical proximal muscle weakness. Laboratory testing showed an elevated CK level of 6,106 U/L. Electrophysiological examination elicited carpal tunnel syndrome and myogenic damage. Muscle MRI revealed diffuse abnormal signals in both lower limbs. Given that muscle symptoms are widely recognized among hypothyroid patients, hypothyroid myopathy was initially suspected, and thyroid hormone tablets were added for a week. However, muscle weakness persisted along with an even higher CK (7,020 U/L). Quadriceps muscle biopsy was performed and indicated inflammatory myopathy. Myositis specific antibodies (MSAs) detection revealed that anti-SRP was positive. A diagnosis of hypothyroidism combined with anti-SRP IMNM was finally made. Treatment of corticosteroid and immunosuppressive agents achieved a positive clinical and biochemical response. This case indicates that hypothyroidism combined with anti-SRP IMNM is a rare clinical entity, possibly caused by a general immunologic dysregulation.

Immune-mediated necrotizing myopathy (IMNM) is characterized by markedly elevated creatinine kinase and histologically scattered necrotic muscle fibers and generally associated with autoantibodies against signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-coA-reductase (HMGCR). Poor clinical response to conventional therapies and relapses commonly occur in severe cases. Anti-B-cell therapies have been used in refractory/relapsing cases.
The characteristics of a patient with IMNM associated with anti-SRP antibodies including physical examination, laboratory tests, and disease activity assessment were evaluated. Conventional therapy, belimumab treatment schedule, and follow-up data were recorded. Medical records of IMNM patients treated in our department from September 2014 to June 2021 were reviewed to evaluate the efficacy and safety of anti-B-cell therapy for anti-SRP IMNM. A literature review of patients with anti-SRP IMNM treated with anti-B-cell therapies was performed.
We describe a case of a 47-year-old woman with IMNM associated with anti-SRP antibodies who relapsed twice after conventional therapy but showed good response and tolerance to belimumab at 28 weeks follow-up. In this review, three patients from our department were treated with rituximab. Two of the three patients rapidly improved after treatment. Twenty patients and five retrospective studies were included in the literature review. All patients were administered rituximab as an anti-B-cell drug.
Despite a lack of rigorous clinical trials, considerable experience demonstrated that anti-B-cell therapy might be effective for patients with IMNM associated with anti-SRP antibodies. Belimumab in association with steroids might be an encouraging option for refractory/relapsing cases.

Immune-mediated necrotizing myopathy (IMNM) is a group of immune-related myopathies characterized by progressive proximal muscle weakness, extremely high serum creatine kinase (CK) levels, and necrotic muscle fibers with a relative lack of inflammation. Treatment of IMNM is challenging, with most cases refractory to high-dose steroids in combination with multiple immunotherapies. The role of rituximab (RTX) for IMNM has been explored in isolated case reports and small series. The aim of this article was to perform a literature review of patients with IMNM treated with RTX and to evaluate RTX efficacy and safety. A total of 34 patients with IMNM were reviewed: 52.9% (18/34) with anti-signal recognition particle (SRP) antibodies and 47.1% (16/34) with anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibodies. Patient age at onset varied from 11 years to 81 years (mean 41 years). The majority of patients presented as a severe proximal muscle weakness and the peak level of CK varied from 3900 IU/L to 56,000 IU/L (mean 18,440 IU/L). Prior to RTX administration, all patients were treated with high-dose steroids and most were treated with multiple immunotherapies. The reason for initiating RTX was that 64.7% (22/34) of patients showed no improvement after previous treatments, and 35.3% (12/34) of patients relapsed when attempting to wean steroids or other immunosuppressive agents. With regard to RTX efficacy, 61.8% (21/34) of patients presented a response to RTX. Our data may support the use of RTX as an effective treatment strategy against IMNM resistant to steroids and multiple immunotherapies. Meanwhile, RTX as a first-line therapy could be a choice in IMNM, particularly in African Americans with anti-SRP antibody-positive subsets. ANA, antinuclear antibody; CK, creatine kinase; HMGCR, 3-hydroxy-3-methylglutaryl-CoA reductase; IMNM, immune-mediated necrotizing myopathy; MAC, membrane attack complex; MHC-I, major histocompatibility complex-I; RTX, rituximab; SRP, signal recognition particle.

A 60-year-old Japanese woman presented with subacute progressive muscle pain and weakness in her proximal extremities. She was diagnosed with influenza A (H3N2) infection a week before the onset of muscle pain. At the time of admission, she exhibited weakness in the proximal muscles of the upper and lower limbs, elevated serum liver enzymes and creatinine kinase, and myoglobinuria. She did not manifest renal failure and cardiac abnormalities, indicating myocarditis. Electromyography revealed myogenic changes, and magnetic resonance imaging of the upper limb showed abnormal signal intensities in the muscles, suggestive of myopathy. Muscle biopsy of the biceps revealed numerous necrotic regeneration fibers and mild inflammatory cell infiltration, suggesting immune-mediated necrotizing myopathy (IMNM). Necrotized muscle cells were positive for human influenza A (H3N2). Autoantibody analysis showed the presence of antibodies against the signal recognition particle (SRP), and the patient was diagnosed with anti-SRP-associated IMNM. She was resistant to intravenous methylprednisolone pulse therapy but recovered after administration of oral systemic corticosteroids and immunoglobulins. We speculate that the influenza A (H3N2) infection might have triggered her IMNM. Thus, IMNM should be considered as a differential diagnosis in patients with proximal muscle weakness that persists after viral infections.