Georgirene D. Vladutiu

Statin-Associated Myopathy with Normal Creatine Kinase Levels

Context Although severe myopathy can occur with statin therapy, some patients receiving statins develop muscle symptoms but have normal serum creatine kinase levels. Contribution This report documents biopsy-confirmed myopathy in four statin-treated patients with normal creatine kinase levels. When patients were challenged with placebo or statin, symptoms and histologic changes occurred only during statin use. Implications Normal creatine kinase levels do not rule out statin-associated myopathy in patients with muscle symptoms. The frequency of this disorder is unknown. The Editors 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are the mainstay of therapy for hypercholesterolemia because of their effectiveness and exceptional safety profile (1-3). Nonetheless, many patients treated with statins have muscle symptoms, and some patients develop severe muscle toxicity. Little is known about the mechanism by which statin therapy leads to muscle toxicity. The recent withdrawal of cerivastatin from the U.S. market has highlighted both our ignorance and the need for postmarketing surveillance of these therapies (4). There are credible reports of patients who have muscle symptoms and normal serum creatine kinase levels while receiving statins. One of us described 15 patients with muscle stiffness and tenderness who had normal levels of creatine kinase. Muscle biopsies in these patients revealed ragged red fibers consistent with mitochondrial myopathy (5). Other researchers have described patients with reproducible muscle pain during statin therapy despite normal creatine kinase levels (6, 7). Cell cultures and animal models have shown statin toxicity despite normal creatine kinase levels (8, 9). Thus, it appears that muscle symptoms of some patients receiving statin therapy might represent a muscle toxicity below the threshold needed to increase creatine kinase levels. We describe four such patients who had myopathy during statin therapy despite normal creatine kinase levels. Methods Four patients were identified among the first 20 patients randomly assigned in an ongoing, unfunded, double-blinded, crossover clinical trial that had been approved by an investigational review board. The objective of the trial is to determine whether patients with muscle symptoms and normal creatine kinase levels while taking statins could distinguish blinded statin therapy from placebo. We hypothesized that some patients would be able to identify blinded statin therapy and have objective findings. Patients who had muscle symptoms during statin therapy that resolved when they were not receiving statins for 2 weeks were recruited from a clinical research group. Eligible patients had to have normal creatine kinase levels while they were experiencing symptoms. End points were 1) whether patients could accurately identify blinded statin therapy and 2) standard measures of functional capacity and muscle strength. The muscular strength tests during both placebo use and statin therapy included hip abduction and flexion measured by Nicholas Manual Muscle Tester (Lafayette Instrument Co., Lafayette, Indiana) (10). The 4 patients presented here were identified during a preliminary analysis of the first 21 patients. These 4 patients correctly identified the statin therapy phase because of the reproducible muscle symptoms. Tissue samples from percutaneous muscle biopsies were fresh frozen in liquid nitrogen for metabolic and genetic analysis and were fixed for pathologic analysis according to standard techniques (11). Pathologists reading the muscle biopsy findings were not blinded to the treatment status of the patients, and requisitions read possible myopathy. Plasma concentrations of HMG-CoA reductase inhibitors were measured by using a validated enzyme inhibition assay (12). The findings of these 4 patients are presented here and summarized in the Table. Table. Patient Characteristics Some muscle specimens were analyzed for mitochondrial point mutations at an accredited mitochondrial disease laboratory by using a standard point mutation analysis panel and Southern blotting techniques. Urine specimens were analyzed for organic acids by using standard mass spectrometry techniques. Results Patient 1 Patient 1 developed muscle aches and decreased exercise tolerance during 4 years of simvastatin therapy. She found it difficult to ascend one flight of stairs without resting to relieve severe leg aching. Symptoms did not change during a brief trial of atorvastatin. After the patient entered the trial, her muscle symptoms markedly resolved during the 2-week washout period and the blinded placebo phase. Muscle aching recurred within 48 hours of initiation of the statin phase. After 2 weeks of statin therapy, the patient again found it difficult to ascend a flight of stairs because of leg pain and weakness. She repeated the protoco l and again experienced symptoms while receiving statin; the symptoms again resolved during the placebo phase. Results of serum and urine biochemical analyses are reported in the Table. Muscle biopsy revealed extensive lipid-filled vacuoles distributed within the myofibers (Figure), along with cytochrome oxidasenegative myofibers. Figure. Muscle biopsy specimens obtained while patients were receiving and not receiving statin therapy. parts A, C, and E parts B, D, and F The patients muscle symptoms and hip weakness improved 3 months after she had discontinued statin therapy. At that point, repeated muscle biopsy showed complete resolution of the pathologic abnormalities (Figure). Patient 2 Patient 2 developed muscle pains and weakness while receiving lovastatin, 40 mg/d. She could not open jars or snap her fingers. Her physician changed her therapy to niacin for 2 years. Each time simvastatin was added to improve her lipid control, the patient developed muscle aches, weakness, and shortness of breath with exertion. She entered the double-blinded trial for two separate evaluations and correctly identified the statin phases because of reproduction of her symptoms. The patient had muscle weakness and normal creatine kinase levels during each statin phase (Table). Muscle biopsy revealed accentuated lipid droplet accumulation and cytochrome oxidasenegative muscle fibers that were consistent with myopathy. Repeated muscle biopsy performed 3 months after discontinuation of statin therapy revealed complete resolution of the abnormal lipid stores. Patient 3 Patient 3 developed aching and weakness of the shoulder, hip, and thigh while taking atorvastatin, 20 mg/d, for 2 years. During a 2-week vacation, he forgot his medication and noticed a substantial resolution of his muscle symptoms. He entered the trial for two separate evaluations and correctly identified the statin arm both times after developing weakness; his creatine kinase level was normal at both evaluations (Table). A muscle biopsy performed during atorvastatin therapy revealed increased lipid droplets, ragged red fibers, and cytochrome oxidasenegative muscle fibers, all consistent with lipid myopathy. Repeated biopsy done after the patient had not received statin therapy for 5.5 months showed resolution of the increased lipid droplets. Patient 4 Patient 4 began receiving atorvastatin, 10 mg/d, for combined hyperlipidemia, and within 2 weeks he noticed leg aches when climbing stairs. His symptoms resolved 2 weeks after he had stopped taking atorvastatin. Upon enrollment in the trial, he correctly identified the blinded statin therapy and had measurable hip weakness despite a normal creatine kinase level (Table). His muscle biopsy demonstrated cytochrome oxidasenegative fibers. Electron microscopy showed abnormal lipid droplets surrounded by electron-dense membranous debris. The patient did not undergo biopsy after discontinuation of statin therapy. Testing We performed a series of tests to exclude possible causes of mitochondrial dysfunction other than statin therapy. Biochemical testing of these patients during statin therapy did not reveal any evidence of carnitine deficiency or hypothyroidism. Discussion Randomized trials and community surveillance have demonstrated an extremely low incidence of serious muscle toxicity in patients receiving statins: 1 case per 10 000 (13, 14). Despite this low incidence, many patients attribute their muscle symptoms to statin therapy. The similar clinical, pathologic, and biochemical features of our four patients suggest that the patients have the same type of myopathy. More important, these features are convincingly related to statin therapy and fulfill the accepted criteria for an adverse drug reaction: 1) Muscle symptoms occurred when the patients were receiving statins in a double-blinded fashion, 2) these symptoms normalized when the patients received placebo, 3) muscle toxicity recurred upon re-exposure to the statin, as it had occurred upon previous exposures, 4) the adverse reaction was confirmed by pathologic and biochemical findings, and 5) the pathologic abnormality reversed upon discontinuation of statin therapy (15). A limitation of our report is that the pathologists were not blinded to the treatment status of the patients at biopsy. Nonetheless, the histochemical findings in these four patients were surprisingly similar. Unusually prominent accumulations of lipid were present in the type 1 fibers on oil red O stains or electron microscopy in all four patients. Other evidence of myopathy included cytochrome oxidasenegative staining fibers and ragged red fibers. These myopathic findings reversed when three of these patients had repeated biopsy while not receiving statins. Increased lipid stores, cytochrome oxidasenegative myofibers, and ragged red fibers are features of mitochondrial respiratory chain dysfunction and suggest myopathy due to a metabolic abnormality. Although some of these findings may rarely occur in myofibers because of aging, the pattern of increased lipid is unusual. It has pre

Statin-associated muscle symptoms: impact on statin therapy—European Atherosclerosis Society Consensus Panel Statement on Assessment, Aetiology and Management

Statin-associated muscle symptoms (SAMS) are one of the principal reasons for statin non-adherence and/or discontinuation, contributing to adverse cardiovascular outcomes. This European Atherosclerosis Society (EAS) Consensus Panel overviews current understanding of the pathophysiology of statin-associated myopathy, and provides guidance for diagnosis and management of SAMS. Statin-associated myopathy, with significant elevation of serum creatine kinase (CK), is a rare but serious side effect of statins, affecting 1 per 1000 to 1 per 10 000 people on standard statin doses. Statin-associated muscle symptoms cover a broader range of clinical presentations, usually with normal or minimally elevated CK levels, with a prevalence of 7–29% in registries and observational studies. Preclinical studies show that statins decrease mitochondrial function, attenuate energy production, and alter muscle protein degradation, thereby providing a potential link between statins and muscle symptoms; controlled mechanistic and genetic studies in humans are necessary to further understanding. The Panel proposes to identify SAMS by symptoms typical of statin myalgia (i.e. muscle pain or aching) and their temporal association with discontinuation and response to repetitive statin re-challenge. In people with SAMS, the Panel recommends the use of a maximally tolerated statin dose combined with non-statin lipid-lowering therapies to attain recommended low-density lipoprotein cholesterol targets. The Panel recommends a structured work-up to identify individuals with clinically relevant SAMS generally to at least three different statins, so that they can be offered therapeutic regimens to satisfactorily address their cardiovascular risk. Further research into the underlying pathophysiological mechanisms may offer future therapeutic potential.

Clinical Spectrum, Morbidity, and Mortality in 113 Pediatric Patients with Mitochondrial Disease

Objectives. The aim of this study was to elucidate the frequency of major clinical manifestations in children with mitochondrial disease and establish their clinical course, prognosis, and rates of survival depending on their clinical features. Methods. We performed a retrospective review of the medical records of 400 patients who were referred for evaluation of mitochondrial disease. By use of the modified Walker criteria, only patients who were assigned a definite diagnosis were included in the study. Results. A total of 113 pediatric patients with mitochondrial disease were identified. A total of 102 (90%) patients underwent a muscle biopsy as part of the diagnostic workup. A significant respiratory chain (RC) defect, according to the diagnostic criteria, was found in 71% of the patients who were evaluated. In this cohort, complex I deficiency (32%) and combined complex I, III, and IV deficiencies (26%) were the most common causes of RC defects, followed by complex IV (19%), complex III (16%), and complex II deficiencies (7%). Pathogenic mitochondrial DNA abnormalities were found in 11.5% of the patients. A substantial fraction (40%) of patients with mitochondrial disorders exhibited cardiac disease, diagnosed by Doppler echocardiography; however, the majority (60%) of patients had predominant neuromuscular manifestations. No correlation between the type of RC defect and the clinical presentation was observed. Overall, the mean age at presentation was 40 months. However, the mean age at presentation was 33 months in the cardiac group and 44 months in the noncardiac group. Twenty-six (58%) patients in the cardiac group exhibited hypertrophic cardiomyopathy, 29% had dilated cardiomyopathy, and the remainder (13%) had left ventricular noncompaction. Patients with cardiomyopathy had an 18% survival rate at 16 years of age. Patients with neuromuscular features but no cardiomyopathy had a 95% survival at the same age. Conclusions. This study gives strong support to the view that in patients with RC defects, cardiomyopathy is more common than previously thought and tends to follow a different and more severe clinical course. Although with a greater frequency than previously reported, mitochondrial DNA mutations were found in a minority of patients, emphasizing that most mitochondrial disorders of childhood follow a Mendelian pattern of inheritance.

Genetic risk factors associated with lipid-lowering drug-induced myopathies.

Lipid‐lowering drugs produce myopathic side effects in up to 7% of treated patients, with severe rhabdomyolysis occurring in as many as 0.5%. Underlying metabolic muscle diseases have not been evaluated extensively. In a cross‐sectional study of 136 patients with drug‐induced myopathies, we report a higher prevalence of underlying metabolic muscle diseases than expected in the general population. Control groups included 116 patients on therapy with no myopathic symptoms, 100 asymptomatic individuals from the general population never exposed to statins, and 106 patients with non–statin‐induced myopathies. Of 110 patients who underwent mutation testing, 10% were heterozygous or homozygous for mutations causing three metabolic myopathies, compared to 3% testing positive among asymptomatic patients on therapy (P = 0.04). The actual number of mutant alleles found in the test group patients was increased fourfold over the control group (P < 0.0001) due to an increased presence of mutation homozygotes. The number of carriers for carnitine palmitoyltransferase II deficiency and for McArdle disease was increased 13‐ and 20‐fold, respectively, over expected general population frequencies. Homozygotes for myoadenylate deaminase deficiency were increased 3.25‐fold with no increase in carrier status. In 52% of muscle biopsies from patients, significant biochemical abnormalities were found in mitochondrial or fatty acid metabolism, with 31% having multiple defects. Variable persistent symptoms occurred in 68% of patients despite cessation of therapy. The effect of statins on energy metabolism combined with a genetic susceptibility to triggering of muscle symptoms may account for myopathic outcomes in certain high‐risk groups. Muscle Nerve, 2006

Novel mutations associated with carnitine palmitoyltransferase II deficiency

The most common form of carnitine palmitoyltransferase II (CPT II) deficiency occurs in adults and is characterized by muscle pain, stiffness, and myoglobinuria, triggered by exercise, fasting, or other metabolic stress. This study reports the molecular heterogeneity of CPT2 mutations and their biochemical consequences among a series of 59 individuals who were suspected of having CPT II deficiency based on the decreased CPT activity observed in muscle or leukocytes samples, clinical findings, or referral for mutation analysis from other laboratories. Only 19 subjects were considered to be at particularly high risk of CPT II deficiency based on review of their clinical symptoms and residual CPT activity. The samples were initially screened for 11 mutations with allele‐specific oligonucleotides (ASO). Extensive sequence analysis was subsequently performed on 14 samples which either had a CPT2 mutation detected by ASO screening or the residual CPT activity was below that observed in ASO positive samples. Three known (P50H, S113L, and F448L) and three novel mutations were identified among 13 individuals in this study. A single nucleotide polymorphism was also identified 11 bp distal to the CPT2 polyadenylation site that will be useful for linkage analysis. Two of the new mutations were single nucleotide missense mutations, R503C and G549D, that occurred in highly conserved regions of the CPT isoforms, and the third was a frameshift mutation, 413 delAG, caused by a 2‐bp deletion upstream of a previously identified missense mutation, F448L. The 413 delAG mutation was the second most common mutation identified in our study (20% of mutant alleles) and all individuals with the mutation were of Ashkenazi Jewish ancestry suggesting a defined ethnic origin for the mutation. Despite rigorous mutation analysis, six of 13 individuals identified with CPT2 mutations remained as heterozygotes. We propose that heterozygosity for certain CPT2 mutations, S113L and R503C, is sufficient to render individuals at risk of clinical symptoms. Hum Mutat 13:210–220, 1999.

Excretion-Reuptake Route of β-Hexosaminidase in Normal and I-Cell Disease Cultured Fibroblasts

It has been proposed that in cultured fibroblasts the final packaging of enzymes in lysosomes requires excretion followed by pinocytosis by neighboring cells via a carbohydrate-specific receptor mechanism. It has also been proposed that the abnormally high activity of lysosomal enzymes in the medium of cultured fibroblasts from patients with I-cell disease (mucolipidosis II) results from an altered carbohydrate recognition residue on the enzymes which prevents reuptake into the cells. With beta-hexosaminidase as a marker, and competitive inhibition of uptake by 2 mM mannose-6-phosphate, we have determined that only 12% of the total (intra- and extracellular) beta-hexosaminidase in normal fibroblasts is channeled through the excretion-reuptake route. After 9 d of exposure to mannose-6-phosphate, normal fibroblast cultures accumulated in the medium only a fraction of the enzyme excreted by I-cell disease fibroblasts in the same period. Furthermore, this minimal loss of enzyme to the medium did not result in a decrease of intracellular enzyme activity. Finally, if the defect in I-cell disease were only because of an impairment of a reuptake mechanism that involves only 12% of the total enzyme, then 88% of the newly synthesized enzyme should be retained by I-cell fibroblasts, resulting in intracellular activity three to nine times higher than that which is observed. These data are consistent with our previous proposal that excessive lysosomal enzyme activity in the medium of I-cell disease fibroblasts results from preferential exocytosis.

Simvastatin–Fluconazole Causing Rhabdomyolysis:

OBJECTIVE: To report a case of rhabdomyolysis after concomitant use of simvastatin, a commonly used hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, and fluconazole, an azole antifungal agent. CASE SUMMARY: An 83-year-old white man with a history of congestive heart failure and hyperlipidemia presented to the hospital 1 week following the addition of fluconazole to a medication regimen that included simvastatin 40 mg once daily. The patient had severe muscle weakness and a markedly elevated serum creatine kinase activity, which resolved following discontinuation of simvastatin and fluconazole. DISCUSSION: Rhabdomyolysis is a recognized adverse effect of HMG-CoA reductase inhibitors (statins), commonly caused by their interaction with other drugs, such as azole antifungals, that inhibit the cytochrome P450 isoenzyme family. An objective causality assessment revealed that the adverse drug event was probable. Although drug interactions have been described for combinations of other HMG-CoA reductase inhibitors and azole antifungals, rhabdomyolysis likely caused by the interaction between simvastatin and fluconazole has not yet been reported. This case reinforces the importance of being vigilant for drug interactions, particularly in connection with commonly prescribed medications such as statins. CONCLUSIONS: Patients receiving statins who have cancer may receive azole antifungals and other drugs that inhibit CYP3A4 during treatment, predisposing them to toxicity. These patients should therefore be monitored closely for drug interactions.

Novel homoplasmic mutation in the mitochondrial tRNATyr gene associated with atypical mitochondrial cytopathy presenting with focal segmental glomerulosclerosis

We report a 9‐year‐old girl with a mitochondrial cytopathy preceded by steroid‐resistant focal segmental glomerulosclerosis (FSGS). The proband presented at the age of 2 years with steroid‐resistant nephrotic syndrome caused by FSGS. Her renal function progressively deteriorated and a dilated cardiomyopathy developed at the age of 7 years. A skeletal muscle biopsy showed a combined respiratory chain (RC) defect and a partial deficiency of coenzyme Q10. A novel mutation in the evolutionary highly conserved region of the mitochondrial tRNATyr gene was found in homoplasmic state in skeletal muscle, blood, and renal tissue. The mutation was also found in homoplasmic state in her mildly symptomatic mother. No other maternal family members were available for testing. The present case of mitochondrial cytopathy initially presenting with steroid‐resistant nephrotic syndrome, unusual biochemical and renal findings associated with a novel tRNA point mutation suggests that steroid‐resistant FSGS can predate other features of mitochondrial disease for a prolonged period of time and that the progressive glomerulopathy associated with combined mitochondrial RC defects is genetically heterogeneous.

Genetic risk for malignant hyperthermia in non-anesthesia-induced myopathies.

Malignant hyperthermia (MH) is a pharmacogenetic, autosomal dominantly inherited disorder of skeletal muscle triggered by volatile anesthetics and infrequently by extreme exertion and heat exposure. MH has variable penetrance with an incidence ranging from 1 in 5000 to 1 in 50,000-100,000 anesthesias. Mutations in the ryanodine receptor gene, RYR1, are found in 50-70% of cases. We hypothesized that a portion of patients with drug-induced muscle diseases, unrelated to anesthesia, such as severe statin myopathy, have underlying genetic liability that may include RYR1 gene mutations. DNA samples were collected from 885 patients in 4 groups: severe statin myopathy (n=197), mild statin myopathy (n=163), statin-tolerant controls (n=133), and non-drug-induced myopathies of unknown etiology characterized by exercise-induced muscle pain and weakness (n=392). Samples were screened for 105 mutations and variants in 26 genes associated with 7 categories of muscle disease including 34 mutations and variants in the RYR1 gene. Disease-causing mutations or variants in RYR1 were present in 3 severe statin myopathy cases, 1 mild statin myopathy case, 8 patients with non-drug-induced myopathy, and none in controls. These results suggest that disease-causing mutations and certain variants in the RYR1 gene may contribute to underlying genetic risk for non-anesthesia-induced myopathies and should be included in genetic susceptibility screening in patients with severe statin myopathy and in patients with non-statin-induced myopathies of unknown etiology.

CPT2 gene mutations resulting in lethal neonatal or severe infantile carnitine palmitoyltransferase II deficiency

Three distinct clinical manifestations of carnitine palmitoyltransferase II (CPT II) deficiency have been defined including a mild adult onset myopathy, a severe infantile disorder and a lethal neonatal form. In this study we have examined the genomic DNA of five patients, 3 with the lethal neonatal form and 2 with the severe infantile form of the disease and identified two disease-causing mutations in the CPT2 gene for each patient, three of which are novel. In addition, based on currently available structural, biochemical and clinical data, we have classified all 64 known disease-causing mutations into groups with different predicted phenotypes depending on their CPT2 allelic counterparts.