Objective weakness, statin-induced muscle disorders

Thanks Celine for presenting a great case! This is a case of an elderly person on a high-intensity statin for secondary prevention after an ischemic CVA with subacute progressive fatigue and proximal bilateral upper and lower extremity weakness found to ultimately have anti-HMGCR antibody positive autoimmune necrotizing myopathy likely secondary to statin use.

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Main points:

  1. ) Per our MKSAP question, patients with suspected myesthenic crisis should prompt ICU consultation for close monitoring of bedside PFTs such as FVC/NIFs for possible need for intubation. Here is an interesting blog post on the art (and evidence) behind when to consider intubation for these patients.
  2. ) Statins can cause a wide spectrum of rare to very rare muscle disorders from myalgias with normal CK to rhabdomyolysis from myonecrosis. Here is a great BMJ clinical review about this.
  3. ) Alan Hunter found this great reference on anti-HMGCR antibody induced myopathy and how only a small percent are secondary to statins.

Want to learn more?

High dose statin for secondary prevention of CVA

The 2006 NEJM industry sponsored SPARCL trial is a classic that examined the question whether patients with an ischemic CVA should be started on a high-intensity statin (specifically atorvastatin 80mg) for secondary prevention. They found the NNT to prevent 1 stroke in 1 year is 258 and at 5 years is 45. Here is the link to read for yourself and the link to our EBM video of Elizabeth Allen, Vinay Prasad and Adam Obley on how to critically appraise a randomized clinical trial on drug therapy

Approach to objective weakness

In the differential of objective muscle weakness, inflammatory myopathies are rare. Also be sure to consider drug/metabolic-induced, endocrine, muscular dystrophy, rheum, and NMJ disorders on the differential. The UpToDate article on this is excellent.

We had a similar case last month of a patient presenting with lower extremity weakness who was ultimately found to have idiopathic inflammatory myopathy. Here is the blog post from that highlighting the diagnoses that fall under inflammatory myopathy.