Seronegative Immune-Mediated Necrotizing Myopathy: A Case Report

Area of Science:

• Rheumatology
• Neurology
• Immunology

Background:

• Idiopathic inflammatory myopathies (IIMs) encompass autoimmune disorders causing muscle weakness.
• Immune-mediated necrotizing myopathy (IMNM) is a specific IIM subtype.
• IMNM classification includes autoantibodies like anti-HMGCR and anti-SRP, or seronegative status.

Observation:

• A 61-year-old female with a history of lung cancer and current statin use presented with subacute proximal lower extremity weakness.
• Laboratory tests revealed markedly elevated creatinine kinase (CK) and amino transaminases.
• The patient exhibited bilateral proximal lower extremity muscle weakness.

Findings:

• Initial inpatient treatment with corticosteroids led to successful outcomes.
• Corticosteroids were discontinued and azathioprine was initiated three months post-admission.
• The patient achieved a 60% increase in muscle strength after treatment.

Implications:

• This case underscores the importance of recognizing IMNM in patients with risk factors like statin use.
• Effective management strategies involving immunosuppressive therapy can lead to significant clinical improvement.
• Further research into IMNM pathogenesis and treatment is warranted.