Objectives Diagnosing the idiopathic inflammatory myopathies (IIMs) can be challenging as several conditions, including genetic myopathies such as limb girdle muscular dystrophy type R12 (LGMD 2 l, anoctaminopathy), mimic the presentation. Here we describe learning points identified from review of four patients with LGMD 2 l who were initially incorrectly diagnosed with IIM. Our aim is to provide clinicians working in adult rheumatology services with a toolkit to help identify non-inflammatory presentations of myopathy. Methods We performed retrospective review of medical notes, laboratory results, muscle imaging and histological findings of four patients with LGMD 2 l who were previously misdiagnosed with IIM. We focused on clinical presentation and progression, therapeutic agents used, and events leading to revision of the diagnosis. Results Three males and one female patients with a mean age of 51 years at presentation were reviewed. In each case treatment with immunosuppressants, in one case for >15 years, was observed without a clear therapeutic response. All patients were negative for anti-nuclear antibodies and available myositis-associated/specific autoantibodies and associated connective tissue disease features were absent. Prominent fatty infiltration and selective muscle involvement on thigh muscle magnetic resonance imaging was a common. Conclusions Adult-onset genetic myopathies, particularly LGMD R12, can mimic IIM. Accurate diagnosis is crucial to avoid use of potentially harmful immunosuppressive therapies, allow appropriate genetic counselling, and facilitate involvement in research studies.
ObjectiveThe idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of immune-mediated systemic disorders that commonly target skeletal muscles. The aim of our review is to remind clinicians to be vigilant of common mimickers, and what red flags to look for to avoid misdiagnosis. Methods We reviewed the clinical documentation and investigation results of illustrative real-life case examples of significant IIM mimickers with valuable learning points. Following an initial diagnosis of IIM, the patients had been referred toour Adult Neuromuscular Service at Salford Royal Hospital Northern Care Alliance NHS Foundation Trust, UK. ResultsFour cases, two males and two females, were analysed. Retrospective review of key case-specific features suggestive of alternative diagnoses were identified and described, prompting a broader discussion of common disease groups that can mimic IIM. ConclusionThe presentation of IIM is heterogeneous and the differential diagnosis wide. Several non-inflammatory conditions can present as mimickers of IIM, each requiring a different management approach.
The idiopathic inflammatory myopathy (IIMs) are a rare heterogenous group of immune-mediated diseases leading to muscle inflammation. Prompt and accurate diagnosis is important so that immunosuppressive treatment can commence and irreversible tissue damage be avoided. Other rare conditions may mimic IIM, making confirmation of diagnosis sometimes difficult.Limb girdle muscular dystrophy type R12 (LGMD 2L, anoctaminopathy) is a recessive genetic myopathy which may present in adulthood and is caused by pathogenic variants in the ANO5 gene. Clinical pres- entation can vary from asymptomatic hyper-CK-aemia to exertional myalgia and/or progressive muscle weakness.Here we present four cases of genetically confirmed LGMD R12 who were initially misdiagnosed with IIM. In each case treatment with immunosuppressants, >15 years in one case, was observed without a clear therapeutic response. All patients were negative for anti-nuclear antibodies and all myositis-associated/specific autoantibodies for which testing is available. Prominent fatty infiltration and selective pattern of muscle involvement on muscle magnetic resonance imaging was also observed.The diagnosis of IIM must be carefully considered in autoantibody-negative patients. Adult-onset genetic myopathies, particularly LGMD R12, are differential diagnoses. Avoidance of potentially harmful immu- nosuppressive therapies, genetic counselling, and involvement in research are key benefits of accurate diagnosis in such cases.italo.marago@nhs.net
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