P079 A challenging case of anti-SRP-associated immune-mediated necrotising myopathy in a young patient Article Swipe

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Syed Adnan Alı Shah , Joy Adepoju , Paula Dospinescu · YOU? · · 2025 · Open Access · · DOI: https://doi.org/10.1093/rap/rkaf111.108

Introduction Idiopathic inflammatory myopathies (IIMs) are a heterogeneous disease group characterised by a subacute course of muscle weakness and inflammatory muscle changes that are presumed to be caused by autoimmune mechanisms. Immune-mediated necrotising myopathy (IMNM) is a distinct subgroup of inflammatory myopathy characterised by myofibre necrosis with minimal inflammatory infiltrates on muscle biopsy, highly elevated creatine kinase levels, and infrequent extra-muscular involvement. We will discuss a case of a 36-year-old lady presenting with nonspecific joint pains with mildly raised CK and anti-CCP positivity without clinical evidence of inflammatory arthritis eventually re-presenting two years later with significant muscle weakness. Case description A 36-year-old morbidly obese female patient initially presented with an episode of self-limited inflammatory arthralgia. There were no features of inflammatory arthritis despite significantly positive anti-CCP antibodies and rheumatoid factor. CRP was elevated at 14 mg/L. LFTs were noted to be deranged with ALT of 100 u/l and AST of 95 u/l. Creatine kinase (CK) was mildly raised at 279. She re-presented two years later with worsening mobility resulting in a fall and a hip dislocation. On examination, there was significant weakness particularly in the lower limbs with leg hip extensors and flexors having significantly reduced power at 2/5 with diminished reflexes in lower limbs. CRP was raised at 60 mg/l and CK was found to be 14000u/l. EMG showed myopathic changes; however, it was a difficult study due to high BMI. There were no extra muscular manifestations. Inflammatory myopathy was suspected and high dose steroids were commenced with DMARD therapy (methotrexate). Extended myositis panel showed anti-SRP positivity with the muscle biopsy identifying necrotising myopathy. Her immunosuppression was therefore augmented with the addition of rituximab. There was slow clinical and biochemical improvement after two doses of rituximab treatment. After initial response, CK remained elevated at 885u/l with clinical improvement having plateaued and the patient still having difficulty standing from a lying position and performing simple daily tasks. Therefore, through collaboration between the neurology and rheumatology team, treatment was augmented by addition of monthly IVIG which resulted in significant improvement in muscle function and CK levels improving to 265u/l. She was also reviewed and managed by the rehabilitation team of physiotherapists and occupational therapist throughout her treatment. The patient has recently expressed her strong wish to pursue pregnancy in the near future which currently poses a therapeutic dilemma around adjustment of immunosuppression to support her, having only just achieved disease remission on combination of immunomodulatory therapies. Discussion IMNM can be classified based on the proposed European Neuromuscular Centre (ENMC) criteria. It can also be characterised by myositis-associated antibodies which guides treatment. Preserving and maximising functional status is the major aim and desirable outcome of treatment. Corticosteroids are the first line of management for quick response. Steroid sparing agents are recommended; however, there are no specific clinical trials to support a specific agent of choice. For anti-SRP disease, rituximab instead or in addition to methotrexate is recommended. Early rituximab is often favoured in anti-SRP disease, as per the ENMC guidelines. Despite early introduction of combination of rituximab and methotrexate, together with corticosteroid, our patient demonstrated active disease both clinically and biochemically, with further improvement following addition of monthly courses of IVIG therapy. Having recently achieved disease stability, the patient is keen to pursue her first pregnancy, which poses several therapeutic dilemmas. Given the severity of her disorder, which requires combined immunosuppression, we need to carefully consider a suitable switch in her treatment which would be safe in pregnancy without jeopardising her prognosis. Other medications used in IMNM include azathioprine, mycophenolate mofetil, tacrolimus, cyclosporine, and cyclophosphamide, though evidence on individual agent efficacy remains limited. Azathioprine is an attractive replacement for methotrexate and IVIG are considered safe in pregnancy. However, we need to ensure disease stability for several months after changing immunosuppression. There are few data available on outcomes of pregnancy in patients with idiopathic inflammatory myopathies (IIM) and the influence of pregnancy on the activity of inflammatory muscle disease. Key learning points 1. Anti-SRP-associated IMNM is associated with significant muscle weakness and disability. 2. Young age of onset is a poor prognosticating factor. 3. Subtle biochemical changes (mildly raised CK and deranged liver function tests) can be picked up earlier in the disease course prior to clinical presentation of actual muscle weakness as in this case. 4. There are no clinical trials to guide management, and treatment is largely based on ENMC guidelines along with expert opinion and clinical observations. 5. An MDT approach is paramount in long-term management. 6. There are very limited data available on outcomes of pregnancy in patients with IIM and the influence of pregnancy on the activity of inflammatory muscle disease.

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P079 A challenging case of anti-SRP-associated immune-mediated necrotising myopathy in a young patient

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2025

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2025-11-01

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Syed Adnan Alı Shah, Joy Adepoju, Paula Dospinescu

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