Anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) immune-mediated necrotizing myopathy (IMNM) is a neuromuscular disorder that presents muscle weakness in proximal extremities and/or the trunk with an elevation of creatine kinase (CK). Young and asymptomatic anti-HMGCR IMNM patients are very rare and a treatment regimen has not been established. The present case, a 17-year-old woman without any muscular symptoms, only showed hyperCKemia that was detected by chance. After close examinations, including a muscle biopsy and antibody search, she was diagnosed as anti-HMGCR IMNM, and initial treatment with methotrexate and continuous intravenous immunoglobulin seemed to be effective. The present case is the unusually young asymptomatic case of anti-HMGCR IMNM. The diagnosis was successfully made, leading to the early introduction of a treatment. Given the course of this case, we believe that the preceding antibody testing is one of the diagnostic option for rhabdomyolysis.

To investigate immune-mediated necrotizing myopathy (IMNM) association with cancer and its clinical implications.
IMNM cases were identified 1 January 2000 to 31 December 2020 matching sex and age controls (4:1).
A total of 152 patients with IMNM were identified and among serologically tested, 60% (83/140) were HMGCR-IgG+, 14% (20/140) were SRP-IgG+ and 26% (37/140) were seronegative. Cancer rates were not significantly different between serological subgroups; 18.1% (15/83) HMGCR-IgG+, 25% (5/20) SRP-IgG+ and 30% (11/37) seronegative (P = 0.34). Cancer screening was performed within 12 months from IMNM diagnosis in 88% (134/152) (whole-body CT plus FDG-PET CT in 53, CT alone in 72 and FDG-PET alone in 9). FDG-PET/CT was positive in 73% (25/34) of cancers. Increasing age was the only risk associated with cancer (P = 0.02). The odds of developing cancer at ±3 or ±5 years from IMNM diagnosis was not higher than controls (OR = 0.49; CI: 0.325-0.76). Lifetime IMNM diagnosis of cancer was less compared with controls (OR = 0.5 CI: 0.33-0.78, P = 0.002). Most patients responded to treatment (137/147, P < 0.001). Death and treatment response did not significantly differ between cancer [23% (8/34); 88% (29/33)] and non-cancer patients [19% (23/118); 92% (108/118)]. In total, 13% (20/152) of patients died during follow-up compared with 14% (41/290) of medicine and 16% (46/290) of neurology controls (P = 0.8). Seropositives had greater life expectancy than seronegatives (P = 0.01).
Greater cancer risk is not observed in IMNM vs controls. Cancer screening in IMNM should be individualized based on age-personal and family history, including consideration of FDG-PET/CT. Immune-treatment response did not differ with cancer.

Anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) related myositis is a form of immune-mediated necrotizing myopathy (IMNM). Anti-HMGCR autoantibodies target HMGCR, a glycoprotein linked to the endoplasmic reticulum implied in the cholesterol synthesis pathway, and exert a pathogenic effect on skeletal muscle cells. More than 60% of patients affected by HMGCR-related myositis shares statin-exposure in their medical history. Patients commonly experience CK levels elevation, myalgia, muscle weakness and soreness at variable extent, which manifest acutely or sub acutely with a progressively worsening course, in some cases mimicking limb-girdle muscular dystrophies (LGMD) phenotype and treatment is based on an immunosuppressive strategy. Here we present the peculiar case of a previously statins-exposed 72 y.o. asymptomatic man with persistent moderate hyperCKemia and high levels of anti-HMGCR, in which pharmacotherapy has not been initiated yet, while a wait-and-see approach has been adopted instead.

A 70-year-old previously independent man developed progressive proximal leg weakness resulting in a fall at home suffering traumatic brain injury. He was prescribed a statin medication two years prior, but this was discontinued on admission to the hospital due to concern for statin myopathy. His weakness continued to progress while in acute rehabilitation, along with the development of dysphagia requiring placement of gastrostomy tube and respiratory failure requiring tracheostomy. Corticosteroids and intravenous immunoglobulin were administered without response. Nerve conduction study demonstrated no evidence of neuropathy; electromyography revealed spontaneous activity suggestive of myopathy. A muscle biopsy was performed and demonstrated myonecrosis. Serology was positive for autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), verifying our diagnosis of statin-associated autoimmune myopathy (SAM). The patient was subsequently treated with rituximab and methotrexate and demonstrated mild clinical improvement. He was eventually liberated from the ventilator. However, later in the course of treatment, he developed respiratory distress and required ventilator support. The patient was discharged to long-term acute care two months after his initial presentation and died due to ventilator-acquired pneumonia three months later. Since their introduction 30 years ago, statin medications have been widely prescribed to prevent cardiovascular diseases. Myalgias and/or myopathic symptoms are among the most recognized side effects of the medication. Statin-associated autoimmune myopathy is a very rare complication of statin use and estimated to affect two to three for every 100,000 patients treated. Clinically, the condition presents as progressive symmetric weakness, muscle enzyme elevations, necrotizing myopathy on muscle biopsy, and the presence of autoantibodies to HMGCR. These findings will often persist and even progress despite discontinuation of the statin. Very few cases of SAM have been described in the literature. Describing this rare condition and the ultimately fatal outcome of our patient, we aim to further understanding of SAM, its presentation and clinical course to promote earlier diagnosis and prompt management.

BACKGROUND: Severe dysphagia may occur in the immune mediated necrotizing myopathies (IMNM). Neck swelling and severe dysphagia as the initial symptoms upon presentation has not been previously described.
METHODS: A 55-year-old male with a 4 week history of neck swelling, fatigue, dysphagia, myalgias, night sweats, and cough was admitted for an elevated CK. He underwent extensive infectious and inflammatory evaluation including neck imaging and muscle biopsy. Neck CT and MRI showed inflammation throughout his strap muscles, retropharyngeal soft tissues and deltoids. Infectious work up was negative. Deltoid muscle biopsy demonstrated evidence of IMNM. Lab tests revealed anti-3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies confirming the diagnosis of HMGCR IMNM.
CONCLUSIONS: HMGCR IMNM is a rare and incompletely understood disease process. Awareness of HMGCR IMNM could potentially lead to earlier diagnosis, treatment and improved clinical outcomes as disease progression can be rapid and severe.