Rapid Clinical Improvement of Anti-HMGCR Immune-mediated Necrotizing Myopathy (IMNM) Treated with Efgartigimod
Quantao Zeng1, Kai Chen1, Li Zeng1, Lixia Xu1, Song Tan2
1Department of Neurology, 2Department of Rare Disease; Department of Neurology, Sichuan Provincial People’s Hospital
Background:
Immune-mediated necrotizing myopathy (IMNM) with anti-HMGCR antibody positivity is characterized by proximal extremity weakness, increased creatine kinase, and extensive muscle edema. There is an urgent need to find more appropriate treatment options for anti-HMGCR IMNM patients who do not respond well to conventional therapy in the acute phase. With the advent of targeted biologics, new treatment options are available.
Results:
We report on a 66-year-old anti-HMGCR IMNM patient who initially presented with a 1-month history of progressive proximal extremity weakness (Manual Muscle Testing-8 [MMT8]: 63 out of 80; Water Swallow Test: grade 2) and dysphagia with markedly elevated creatine kinase. The patient did not respond to conventional high-dose glucocorticoid and intravenous immunoglobulin therapy, and his symptoms rapidly deteriorated over the 2 weeks after this treatment (MMT8: 48 out of 80; Water Swallow Test: grade 4), with worsening limb weakness that prevented walking, marked proximal muscle atrophy, and weight loss. After one cycle (four infusions) of efgartigimod, the patient’s symptoms improved markedly (MMT8: 74 out of 80, Water Swallow Test: grade 1) and he has since (for several months) remained in a good clinical state.
Conclusions:
There are no previous studies or case reports on the use of efgartigimod in patients with anti-HMGCR IMNM, and our case provides some limited experience in this regard.
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