Autophagy in non-immune-mediated rhabdomyolysis: Assessment of p62 immunohistochemistry.

INTRODUCTION/AIMS: p62 immunochemistry (IHC) has been shown to aid diagnosis with distinct patterns of muscle fiber staining observed in some inflammatory, hereditary, and degenerative myopathies, such as immune-mediated necrotizing myopathy (IMNM). The pattern of p62 staining may help narrow the pathological differential diagnosis of rhabdomyolysis. However, there is a lack of information on the pattern of p62 IHC in non-immune-mediated rhabdomyolysis. In this study we aim to describe histopathological findings in non-immune-mediated rhabdomyolysis, with particular emphasis on the pattern of p62 IHC. METHODS: We retrospectively reviewed the histopathological features of patients with a confirmed diagnoses of non-immune-mediated rhabdomyolysis referred to our center. RESULTS: Five patients were identified. Rhabdomyolysis was determined to be due to statin-associated toxicity in three patients, alcohol overuse in one patient, and intensive exercise in one patient. All patients showed increased numbers of necrotic and regenerating muscle fibers. Diffuse and finely granular sarcoplasmic positive p62 staining was present in scattered non-necrotic muscle fibers in all patients. DISCUSSION: Disturbance of autophagy appears to be a common mechanism in non-immune-mediated rhabdomyolysis. Our results show p62 IHC is sensitive but lacks specificity. Therefore, the pattern of p62 staining does not distinguish non-immune-mediated rhabdomyolysis from histopathologically similar IMNM.

Neuromuscular Complications of Statin Therapy.

PURPOSE OF REVIEW: This review provides an overview of neuromuscular side effects associated with statin use, their diagnosis, and treatment. RECENT FINDINGS: The discovery of anti-HMGCR antibodies led to a better understanding of clinical aspects of statin-associated anti-HMGCR myopathy and its treatment. Statins are widely prescribed medications with well-established benefits in the treatment of cardiovascular diseases and stroke. Adherence to statins is influenced by development of side effects, especially muscle related. There is wide range of neuromuscular side effects associated with statin therapy. Documented neuromuscular side effects include asymptomatic elevation of muscle enzymes, mild-moderate myalgias and cramps, toxic and immune-mediated severe necrotizing myopathy, and rare cases of rhabdomyolysis. In addition, statins can lead to unmasking or triggering of underlying muscle and neuromuscular junction disorders. This article identifies the risk factors and provides a review of neuromuscular side effects associated with statin use, their diagnosis and treatment.

The composition of cellular infiltrates in anti-HMG-CoA reductase-associated myopathy.

INTRODUCTION: To characterize cellular infiltrates in muscle biopsies from patients with anti-3-hydroxy-3-methyl-gulatryl-CoA reductase (HMGCR)-associated myopathy. METHODS: Biopsies from 18 anti-HMGCR myopathy and 7 control dermatomyositis patients were analyzed. RESULTS: CD4+ and CD8+ T-cells were scattered within the endomysium in 50% of anti-HMGCR biopsies. All anti-HMGCR biopsies included increased endomysial and/or perivascular CD163+ M2 macrophages; CD11c+ M1 macrophages were present in 18.8%. CD123+ plasmacytoid dendritic (PD) cells were observed within the endomysium and perivascular spaces in 62.5% of anti-HMGCR biopsies. Membrane attack complex was deposited on endothelial cells in 50% and on the sarcolemma of nonnecrotic muscle fibers in 85.7% of anti-HMGCR cases. Major histocompatibility complex class I antigen was up-regulated in 87.5% of the anti-HMGCR cases. CONCLUSIONS: In addition to necrosis, scattered CD4+, CD8+, and PD cells are characteristic of anti-HMGCR myopathy. Predominant M2 polarization suggests infiltrating macrophages are more likely to be involved with tissue repair than destruction.

Six Years Follow-Up of an 11-Year-Old Girl with Anti-HMGCR Myopathy.

Anti-HMGCR myopathy is decribed as an immune-mediated necrotizing myopathy which is characterised by subacute, progressive proximal muscle weakness and elevated creatine kinase (CK) level. In pediatric population, anti-HMGCR myopathy has been reported solely as small case reports, albeit rare. Although treatment consensus has not yet been established, proper treatment with several immunomodulators to include IVIg can show remarkable improvement. We report an 11-year-old-girl diagnosed with anti-HMGCR myopathy with 6 years of follow-up.

Statin-Induced Anti-3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase (Anti-HMGCR) Myopathy.

Statins are known to pharmacologically target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR). Several subtypes of anti-HMGCR autoimmune myopathies have been reported as a result of statin use. Although these types vary widely, a severe and rare form of statin-induced myopathy is immune-mediated necrotizing myopathy (IMNM), resulting in severe muscle injury that does not respond to statin cessation and is associated with poor outcomes. Diagnosis is confirmed through biopsy confirming the necrosis of biopsy fibers, in addition to elevated anti-HMGCR serum levels. Management lacks proper guidelines, however, immunosuppressive therapy has been proposed as a possible intervention. The aim of this report is to increase providers' knowledge of the presentation and possible treatment of statin-induced immune-mediated necrotizing myopathy.

Anti-HMGCR myopathy overlaps with dermatomyositis-like rash: a distinct subtype of idiopathic inflammatory myopathy.

OBJECTIVE: To characterize the clinical and pathological features of anti-HMGCR myopathy. METHODS: The presence of anti-HMGCR antibody in the serum of 227 patients with idiopathic inflammatory myopathy (IIM) and 100 healthy control individuals was assessed by ELISA. All ELISA positive samples were retested by indirect immunofluorescence assay (IIFA) on HEK293 cells. The clinical findings, muscle pathological features, and treatment outcomes of patients with anti-HMGCR myopathy, along with comparisons between anti-HMGCR myopathy with and without dermatomyositis (DM)-like skin rashes, and among MSA-based subgroups were analyzed. RESULTS: We established an optimized ELISA cutoff for anti-HMGCR antibody positivity as ≥ 5.28 U. The overall concordance between ELISA and IIFA was 96.83%. Twenty-one out of 227 IIM patients were anti-HMGCR-positive by both assays. Of these 21 patients, 9 had DM-like skin rashes, and 16 showed remarkable muscle inflammation; 5 patients were juvenile-onset, and 2 received statin treatment. The muscle biopsies from these patients demonstrated variable muscle necrosis and T cell infiltration. Most anti-HMGCR-positive patients achieved favorable outcomes following prednisone and additional immunotherapies. The anti-HMGCR myopathy patients with DM-like rashes, compared to those without DM-like rashes, were younger and had a shorter disease duration. CONCLUSIONS: Optimization of cutoff of anti-HMGCR antibody assays with confirmation by alternative assays can result in higher sensitivity and specificity. DM-like skin rashes and lymphocytic infiltrates were not rare in patients with anti-HMGCR myopathy. These findings suggest that while anti-HMGCR myopathy may overlap with DM-like rash, it is pathologically different from classic DM, and should be considered a distinct subgroup of IIM.

Slowly Progressive Limb-Girdle Weakness and HyperCKemia - Limb Girdle Muscular Dystrophy or Anti-3-Hydroxy-3-Methylglutaryl-CoA-Reductase-Myopathy?

BACKGROUND: Anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR)-myopathy is a usually rapidly progressive form of immune-mediated necrotizing myopathy (IMNM). Rarer clinical courses show slow progression and resemble the phenotype of limb-girdle dystrophy (LGMD). OBJECTIVE: We demonstrate the difficulties in differentiating LGMD versus anti-HMGCR-myopathy. METHODS: We report on a 48-year-old patient with slowly progressive tetraparesis and hyperCKemia for more than 20 years. RESULTS: Due to myopathic changes in initial and second muscle biopsy and typical clinical presentation, the patient was diagnosed with LGMD 20 years ago; despite comprehensive genetic testing including exome diagnostics, the genetic cause of disease could not be identified. Finally, HMG-CoA reductase antibodies were detected, confirming the diagnosis of anti-HMGCR-myopathy. By re-work-up of a second muscle biopsy specimen from year 2009, the diagnosis of a IMNM was made in retrospect. Seven cycles of high-dose immunoglobulins were administered; patient reported outcome measures have mildly improved. CONCLUSION: Patients with clinical LGMD phenotype, degenerative changes in muscle biopsy but without genetic confirmation of the disease should be tested for HMG-CoA-myopathy, thereby allowing for an early start of treatment.

Maintenance treatment with subcutaneous immunoglobulins in the long-term management of anti-HMCGR myopathy.

We describe the clinical response to long-term subcutaneous immunoglobulins (SCIg) in anti-3­hydroxy-3-methyl-glutaryl-coenzyme-A-reductase (anti-HMCGR) myopathy previously treated with intravenous immunoglobulins (IVIg). We collected data from patients affected by anti-HMGCR myopathy, switched from IVIg to SCIg therapy, after achieving clinical stabilization. The Medical Research Council sum score, creatine kinase (CK) levels, and anti-HMGCR antibodies were used to assess the response. We identified three patients with anti-HMGCR myopathy treated with SCIg with a favourable clinical course, allowing the maintenance of clinical stability, the reduction or suspension of steroids therapy and in two of them a complete CK normalization. Finally, anti-HMGCR antibodies tested in all patients after 12 months from SCIg starting, showed a global decrease. SCIg represent an useful alternative to long-term IVIg as already well known in several autoimmune neuromuscular disorders and inflammatory myopathies with advantages of lower side effects and home self-administration.

Statin-induced anti-HMGCR myopathy: successful therapeutic strategies for corticosteroid-free remission in 55 patients.

OBJECTIVE: To describe successful therapeutic strategies in statin-induced anti-HMGCR myopathy. METHODS: Retrospective data from a cohort of 55 patients with statin-induced anti-HMGCR myopathy, sequentially stratified by the presence of proximal weakness, early remission, and corticosteroid and IVIG use at treatment induction, were analyzed for optimal successful induction and maintenance of remission strategies. RESULTS: A total of 14 patients achieved remission with a corticosteroid-free induction strategy (25%). In 41 patients treated with corticosteroids, only 4 patients (10%) failed an initial triple steroid/IVIG/steroid-sparing immunosuppressant (SSI) induction strategy. Delay in treatment initiation was independently associated with lower odds of successful maintenance with immunosuppressant monotherapy (OR 0.92, 95% CI 0.85 to 0.97, P = 0.015). While 22 patients (40%) presented with normal strength, only 9 had normal strength at initiation of treatment. CONCLUSION: While corticosteroid-free treatment of anti-HMGCR myopathy is now a safe option in selected cases, initial triple steroid/IVIG/SSI was very efficacious in induction. Delays in treatment initiation and, as a corollary, delays in achieving remission decrease the odds of achieving successful maintenance with an SSI alone. Avoiding such delays, most notably in patients with normal strength, may reset the natural history of anti-HMGCR myopathy from a refractory entity to a treatable disease.

Anti-HMG-CoA reductase myopathy, an undesirable evolution of statin induced myopathy: a case report.

Statins are commonly used lipid lowering agents which play a pivotal role in reducing cardiovascular morbidity and mortality. Often well tolerated, these HMG-CoA reductase (HMGCR) inhibitors can sometimes cause severe muscle weakness and elevated creatinine kinase (CK) often labeled as statin intolerance or statin induced myopathy. These symptoms improve after discontinuation of the offending drug along with normalization of the enzyme levels. However, an entity called Immune Mediated Necrotizing Myopathy (IMNM), a type of autoimmune mediated myopathy, has been recognized and characterized in patients with history of statin exposure where there is persistence of proximal muscle weakness, CK elevation and myofiber necrosis can be seen on muscle biopsy even after stopping statins. With the increased use of statins, there seems to be a higher incidence of IMNM cases in recent years. Here we discuss a case of anti-HMG-CoA myopathy, one of the three recognized types of IMNM that has been more commonly associated with statin exposure and highly responsive to immunotherapy.

Anti-HMGCR Myopathy.

Anti-HMGCR myopathy was first recognized and characterized in patients with a history of statin exposure and immune-mediated necrotizing myopathy. After the discovery of anti-HMGCR autoantibodies, several international groups identified and characterized more patients, expanding the phenotypic spectrum of this disease to include pediatric patients and young adults without statin exposure and those with a chronic myopathy resembling limb-girdle muscular dystrophy. We provide a summary of clinical findings, pathologic features, muscle imaging, and immunogenetic risk factors of the disease. We also discuss the current treatment strategies and approaches to monitoring the therapeutic response. Lastly, we briefly summarize the current understanding of the pathophysiology of the disease and postulate a model for autoimmunity initiation and propagation in this disease.