Did Shiitake Mushrooms Induce Immune-Mediated Necrotizing Myopathy?

Valentyn Volkov / shutterstock.com

Idiopathic inflammatory myopathies are heterogenous, acquired immune-mediated muscle diseases. Over the past decade, immune-mediated necrotizing myopathy has been recognized as a subcategory of idiopathic inflammatory myopathy characterized by myofiber necrosis in the absence of prominent inflammatory cells.¹ Autoantibodies against signal recognition particle (SRP) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) are thought to be associated with the development of immune-mediated necrotizing myopathy. The latter was originally identified in patients exposed to statin in the U.S. and was initially thought to be specific to statin-associated necrotizing myopathy.² In East Asia, however, the rate of statin-naive immune-mediated necrotizing myopathy seems to be much higher than in North America.^3-5

In this article, we present a case of statin-naive, anti-HMGCR and anti-SRP antibody-positive immune-mediated necrotizing myopathy possibly associated with the daily ingestion of shiitake mushrooms (Lentinula edodes).

Case Report

A 73-year-old man visited our hospital because of myalgia and a high serum creatine kinase (CK) level (1,169 IU/L). Eight months previously, his CK was found to be high at a routine health checkup. Five months previously, he had developed diffuse myalgia over the shoulders, back and thighs. He also noted mild difficulty climbing up stairs, but otherwise he did not notice any muscle weakness. He denied fever, weight loss, joint pain, skin rash, Raynaud’s phenomenon, cough or dyspnea. He had a past medical history of hypertension, gastric ulcer, and lumbar disc herniation. He was taking amlodipine, but had never taken a statin.