The perils of myositis mimickers with illustrative case reports

Objective: The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of immune-mediated systemic disorders that commonly target skeletal muscles. The aim of this article 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 to our Adult Neuromuscular Service at Salford Royal Hospital Northern Care Alliance NHS Foundation Trust, UK.

Results: Four 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.
Conclusion: The 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.