Diagnostic evaluation of clinically normal subjects with chronic hyperCKemia

Association of Plasma Creatinine Phosphokinase Elevation and a History of Idiopathic Cardiomyopathy in Recipients of Heart Transplant

Plasma creatinine phosphokinase (CPK) elevation is frequent after heart transplantation. In the present study, we tested the hypothesis that this CPK elevation is related to idiopathic cardiomyopathy as primary cardiac disease. We included 203 patients who survived >1 year after heart transplantation. Plasma CPK was measured every 4 months during a 15.1 ± 7.7-year follow-up. In univariate analysis, CPK elevation was significantly associated with age at transplantation, length of follow-up, treatment with everolimus, and idiopathic cardiomyopathy as primary cardiac disease. In multivariate analysis, idiopathic cardiomyopathy and length of follow-up were the only significant predictors of CPK elevation (p = 0.002 and p = 0.0001, respectively). A subgroup of 19 patients had frequent CPK elevation (>20% of the dosages). All these patients but 1 had an idiopathic cardiomyopathy as primary disease. In 5 of these 19 patients, we identified a syndrome known to affect both cardiac and skeletal muscles. In conclusion, underlying idiopathic cardiomyopathy is a major determinant of plasma CPK elevation after heart transplantation. Our results show that besides well-described syndromes associating skeletal and cardiac muscle disease, idiopathic cardiomyopathy may be associated with subclinical skeletal muscle myopathy.

What Is in the Myopathy Literature?

ABSTRACT

This update begins with the results of a positive trial of intravenous immunoglobulin in dermatomyositis and a study of molecular and morphologic patterns in inclusion body myositis that may explain treatment refractoriness. Single center reports of muscular sarcoidosis and immune-mediated necrotizing myopathy follow. There is also a report of caveolae-associated protein 4 antibodies as a potential biomarker and cause of immune rippling muscle disease. The remainder covers updates on muscular dystrophies as well as congenital and inherited metabolic myopathies with an emphasis on genetic testing. Rare dystrophies, including one involving ANXA11 mutations and a series on oculopharyngodistal myopathy, are discussed.

Causes of HyperCKemia in Children: A Retrospective Cohort Study

Background and Objectives: Creatine kinase (CK) is a commonly used screening test for neuromuscular disorders (NMDs). However, hyperCKemia can result from several pathologic and physiologic causes. We analyzed neuromuscular disorders in noninfant children with hyperCKemia including those with no weakness and mild CK elevations (<5 times the upper limit of normal). We hypothesized that children with mild CK elevation and no weakness would be unlikely to have neuromuscular disorders and require additional evaluation. Methods: We retrospectively evaluated patients between 1 and 18 years of age seen at a single children's hospital over a 3-calendar-year period with initial total CK values greater than the upper limit of normal with at least 2 years of follow-up data. Final diagnoses were analyzed and associations with possible risk factors assessed. Receiver operating characteristic curves were generated to assess altering CK cutoff values. Results: Of 260 subjects with hyperCKemia, 18 had a neuromuscular disorder (6.9%, 95% confidence interval [CI] 4.2%-10.9%). Of 166 subjects with CK <5 times the upper limit of normal and no weakness, 8 had a neuromuscular disorder (4.8%, 95% CI 2.3%-9.6%). Weakness (odds ratio [OR] 32.5, 95% CI 4-385, P = .0002), and family history of neuromuscular disorders (OR not calculable, P = .0003) were associated with neuromuscular disorders. An optimal CK threshold of 777 was identified on receiver operating characteristic curve analysis (sensitivity of 72% and specificity of 64%). The most commonly identified neuromuscular disorders were muscular dystrophies, inflammatory myopathies, and metabolic myopathies. Conclusion: Most children with hyperCKemia will not be diagnosed with a neuromuscular disorder, but a significant minority even with mild hyperCKemia and without weakness may warrant additional evaluation.

Case Report: Persistent Moderate-to-Severe Creatine Kinase Enzyme Activity Elevation in a Subclinical Dog

A 4-year-old, male-castrated, mixed breed dog was presented for a routine wellness examination at which time a moderate increase in serum creatine kinase (CK) enzyme activity (hyperCKemia) (15,137 IU/L; reference interval 10–200 IU/L), and moderate increases in alanine transaminase and aspartate aminotransferase enzyme activities were first identified. There was no history of clinical abnormalities (e.g., lethargy, lameness, anorexia, dysphagia, weakness, gait abnormalities, or exercise intolerance) and the physical examination was unremarkable. The dog was screened for several relevant potential infectious diseases known to cause inflammatory myopathies and was treated empirically with clindamycin. The serum total CK enzyme activity remained increased, which prompted recommendations for an echocardiogram, electromyogram (EMG), and muscle biopsy acquisition. The echocardiogram and electrocardiographic monitoring were unremarkable. The EMG and muscle biopsies were declined by the owner. The dog was evaluated several times in the subsequent 5 years and remained subclinical with unremarkable physical examinations despite a persistent moderate-to-severe hyperCKemia. Differential diagnoses considered most likely in this dog were an occult/latent hereditary muscular dystrophic disorder or idiopathic hyperCKemia, a phenomenon not yet reported in the veterinary literature. This report describes for the first time, clinical and diagnostic features of a subclinical dog with persistent moderate-to-severe hyperCKemia.

Muscle biopsy: what and why and when?

Skeletal muscle biopsy remains an important investigative tool in the diagnosis of a variety of muscle disorders. Traditionally, someone with a limb-girdle muscle weakness, myopathic changes on electrophysiology and raised serum creatine kinase (CK) would have a muscle biopsy. However, we are living through a genetics revolution, and so do all such patients still need a biopsy? When should we undertake a muscle biopsy in patients with a distal, scapuloperoneal or other patterns of muscle weakness? When should patients with myositis, rhabdomyolysis, myalgia, hyperCKaemia or a drug-related myopathy have a muscle biopsy? What does normal muscle histology look like and what changes occur in neurogenic and myopathic disorders? As with Kipling's six honest serving men, we hope that by addressing these issues we can all become more confident about when to request a muscle biopsy and develop clearer insights into muscle pathology.

Clinical Presentation and Laboratory Findings in Men Versus Women with Myocarditis

Objectives: Understanding sex differences in myocarditis is crucial to improve clinical care. We sought to investigate sex differences focusing on clinical presentation and laboratory parameters. Methods: From 2011 to 2018, 77 patients were diagnosed with myocarditis according to European Society of Cardiology (ESC) criteria with available clinical, laboratory, and cardiac magnetic resonance imaging data. First, we investigated sex differences of clinical and laboratory parameters in the entire cohort of 77 patients. Second, we focused on patients with acute myocarditis (n = 51) defined as recent symptom onset (≤10 days). Results: Myocarditis was present in 63 men (82%) and 14 women (18%). While men most frequently presented with chest pain (78%), a considerable amount of women presented with dyspnea as the only symptom (40%). Within the entire cohort, only creatinine kinase (CK) was higher in men versus women (364 ± 286 vs. 147 ± 148 U/L, p = 0.007), while in patients with acute myocarditis both CK and myoglobin (Mb) were higher in men versus women (CK: 327 ± 223 vs. 112 ± 65 U/L, p = 0.004 and Mb: 111 ± 126 vs. 25 ± 29 μg/L, p = 0.04). No sex differences were found for high-sensitivity troponin T, C-reactive protein, and NT-probrain natriuretic peptide. Conclusions: This is the first study reporting sex differences in clinical presentation and routine laboratory parameters in myocarditis. While clinical presentation appeared to be subtle in women with dyspnea being the only presenting symptom of myocarditis in a considerable part, men typically complained of chest pain. Similarly to observations in myocardial infarction, atypical symptoms and underdiagnosis may be a cause for under-representation of women in cohorts of myocarditis.

McLeod syndrome: Five new pedigrees with novel mutations

OBJECTIVE

To present five new McLeod Syndrome (MLS) pedigrees with novel XK gene mutations, review the literature of this disorder, and discuss the typical and atypical clinical features noted with these new mutations.

METHODS

This is a multi-center retrospective review of five MLS cases with novel gene mutations. Genotypic and phenotypic information has been obtained from each center.

RESULTS

Five novel mutations are reported in this Case series. New clinical findings include prolonged asymptomatic elevated creatine kinase (CK) levels, vocal tics, presence of obstructive sleep apnea (OSA), and one patient of Vietnamese ethnicity.

CONCLUSIONS

We expand on the clinical and genetic spectrum of MLS demonstrating the clinical variability of MLS.

Myalgia with the presence of pathologic EMG correlates with perimysial inflammatory infiltrates

Objective

We aimed to define normal numbers of inflammatory cells in muscle biopsies and to identify the predictive value of isolated muscle pain and increased creatine kinase regarding the diagnosis of myositis.

Methods

We analyzed muscle biopsies of 71 patients using immunostains for CD3+, CD4+, CD8+, CD68+, major histocompatibility complex class I, perforin, and myeloid-related protein (MRP) 8. Patients were categorized as follows—group 1: myalgia without further clinical or laboratory abnormalities (n = 24); group 2: asymptomatic elevation of creatine kinase (hyperCKemia, n = 26); group 3: myalgia and pathologic EMG findings (n = 9); and group 4: otherwise healthy controls who had malignant hyperthermia susceptibility testing (n = 12).

Results

In the normal muscle biopsy specimens from group 4, mean endomysial macrophage (CD68+) density was 21.7 ± 5.6/mm2, and perimysial density was 13.0 ± 5.6/mm2. Numbers of T-lymphocytes (CD3+) were 5 ± 3.5 endomysially and 2.2 ± 3.9/mm2 perimysially. This was not different from groups 1 and 2. Only group 3 patients had increased mean numbers of perimysial macrophages (24.1 ± 6.3/mm2; p = 0.0005), CD3+ (7.6 ± 4.9/mm2; p = 0.0056), and CD8+ T-lymphocytes (5.4 ± 3.1/mm2; p = 0.0008) and displayed the activation marker MRP8 in all cases. Although inflammatory cells were increased in the perimysium in group 3, histology did not fulfill the criteria for dermatomyositis, polymyositis, or inclusion body myositis.

Conclusions

Normal muscle contains a considerable number of macrophages and T-lymphocytes. Muscle biopsy is likely to detect inflammatory changes in patients with myalgia or hyperCKemia only if pathologic EMG findings are present.

Elevated Creatine Kinase in a 6-Year-Old Boy

Paucisymptomatic or asymptomatic but persistently elevated serum creatine kinase is not an uncommon pediatric neurology referral question. The challenge is in promptly identifying etiologies with specific treatments, even if they are rare. The presenting features for a child or adolescent with juvenile-onset Pompe disease (JOPD) can be nonspecific and heterogeneous. Clinical manifestations can appear at any age after 2 years and before adulthood, with insidious onset of symptoms related to slowly progressive skeletal or respiratory muscle weakness. This reported case highlights the importance of screening for JOPD in children with "hyper-CK-emia." Dried blood spot measuring acid α-glucosidase enzyme activity is reliable, rapid, noninvasive, and inexpensive, allowing early diagnosis. Diagnosis of JOPD is important as enzyme replacement therapy with alglucosidase alpha, an intravenous recombinant α-glucosidase, is available, and early treatment improves muscle function, quality of life, and long-term survival.

Creatine kinase is associated with reduced inflammation in a general population: The Tromsø study

Background

Creatine kinase (CK) has been associated with reduced inflammation in obesity while inflammation is associated with obesity-related cardiovascular diseases. We investigated the relationship between CK and high sensitive C-reactive protein (hs-CRP) in a general population.

Methods

CK and hs-CRP were measured in the population-based Tromsø study that included entire birth cohorts and random samples of citizens between 30–87 years of age. The analyses were performed sex-stratified in 5969 men and 6827 women.

Results

CK correlated negatively with hs-CRP in men (r = -0.08, P <0.001) and women (r = -0.06, P <0.001). In univariable regression analyses, CK associated negatively with hs-CRP in men (ß = -0.14, 95% CI -0.19 to -0.10, P <0.001) and women (ß = -0.13, 95% CI -0.18 to -0.08, P <0.001). Mean CK declined from the 2. to the 4. quartiles of hs-CRP in both genders (P <0.001 for trends). There were positive correlations between CK and body mass index (BMI) in men (r = 0.10, P <0.001) and women (r = 0.07, P <0.001). Multiple regression analyses showed a 0.13 unit decrease in hs-CRP (mg/dl) per unit CK increase in men (95% CI -0.35 to -0.20) and 0.29 mg/dl in women (95% CI -0.36 to -0.21) when adjusted for age, BMI, lipids, s-glucose, s-creatinine, transaminases and coronary heart disease.

Conclusion

CK were inversely and independently associated with hs-CRP in a general population. These data provide evidence that CK might have anti-inflammatory properties, but the mechanism and clinical implications are unclarified.

Spectrum of Neuromuscular Disorders With HyperCKemia From a Tertiary Care Pediatric Neuromuscular Center

Elevated creatine kinase is a useful screening test in the diagnostic workup of patients with neuromuscular disorders. We did a retrospective study of children with hyperCKemia (>175 IU/L) who were followed in the neuromuscular program of a tertiary care pediatric center from 2005 to 2016. Patients with hyperCKemia were divided into 2 groups: myopathic and nonmyopathic. Within the myopathic group, there were 3 arbitrary subgroups based on creatine kinase values: A (creatine kinase >10 times normal), B (creatine kinase 5-10 times normal), and C (creatine kinase 1-5 times normal). The 3 major categories of myopathies across all the subgroups were muscular dystrophies (commonest) followed by metabolic myopathies and inflammatory myopathies. Among the nonmyopathic causes of hyperCKemia, spinal muscular atrophy was the commonest. Muscular dystrophies should be considered in children with hyperCKemia, muscle weakness, or calf hypertrophy, and metabolic myopathies to be considered in children with recurrent rhabdomyolysis.

Approach to the Patient With HyperCKemia

PURPOSE OF REVIEW

Neurologists commonly receive consultation requests regarding the evaluation of patients with an elevated serum creatine kinase (CK), a condition known as hyperCKemia. This article outlines an approach to the history and examination of patients with hyperCKemia in order to narrow the localization and differential of an elevated CK and guide possible next steps. This article aims to help clinicians identify treatable or reversible etiologies as well as those that will change management.

RECENT FINDINGS

An unrevealing patient history (assessing for acquired and hereditary etiologies) in an otherwise neurologically intact individual who has a normal nerve conduction study and EMG predicts that the likelihood of diagnosing the patient after further investigations will be quite low. After a comprehensive workup, a positive diagnosis is made in approximately 25% of cases of hyperCKemia.

SUMMARY

The best predictors for added diagnostic yield with further testing in hyperCKemia are a higher level of CK and a younger age; the presence of weakness increases the likelihood of a specific cause other than idiopathic or familial hyperCKemia. Many etiologies do not yet have treatments that alter clinical outcomes, and, even in the absence of a specific diagnosis, good communication with patients and primary care providers remains essential to ensure longitudinal surveillance with expectant management for potential consequences. Many patients with hyperCKemia of uncertain etiology, however, will not develop significant muscle disease on longitudinal follow-up.

Evaluation prevalence of Pompe disease in Iranian patients with myopathies of unknown etiology

Background

Pompe disease is a rare but potentially treatable metabolic disorder having an estimated worldwide incidence of one in forty thousand live births. While the introduction of enzyme replacement therapy (ERT) has considerably increased the awareness of the disease, the delay in diagnosis is still consistent and most patients go undetected.

Objective

This study aimed to determine the prevalence of late-onset Pompe disease (LOPD) in a high-risk population, using dried blood spot (DBS) as a main screening tool.

Methods

This cross-sectional study was performed on the 93 patients who attended to the neuromuscular center of Bu-ali hospital in Tehran, Iran, during 2014–2015. Inclusion criteria were: 1) age ≥1 years, 2) proximal myopathies of unknown etiology in lower limbs or symptoms of limb girdle muscle weakness (LGMW), and 3) unexplained elevated CPK (>174). Acid α-glucosidase (GAA) activity was measured separately on DBS by fluorometric method. For the final diagnosis, GAA deficiency was confirmed by a biochemical assay in skeletal muscle, whereas genotype was assessed by GAA molecular analysis. All statistical tests were performed using the SPSS version 16. Results are presented as mean (SD) or median (IQR), as appropriate.

Results

In a 12-month period, we studied 93 cases: 5 positive samples (5.3%) were detected by DBS screening, biochemical and molecular genetic studies finally confirmed LOPD diagnosis in 3 cases (3.22%). Among the 93 patients, 100% showed hyperCKemia, 89 patients (95.7%) showed LGMW and 4 patients had symptoms of proximal myopathies in the lower limb.

Conclusions

Results from the LOPED study suggest that GAA activity requires accurate screening by DBS in all patients referred for hyperCKemia and/or LGMW.

A Case of Asymptomatic Inclusion Body Myositis

OBJECTIVES

To present a case of asymptomatic inclusion body myositis.

METHODS

The authors report a case of a 67-year-old man who presented with idiopathic hyperCKemia. Physical examination including a complete neurological evaluation was unremarkable. Systemic causes of hyperCKemia, including medication side effects, metabolic and endocrine disorders, and connective tissue disorders, were ruled out with various indicated tests.

RESULTS

Two and a half years after initial consultation, the patient reported left knee pain. Magnetic resonance imaging of the left knee showed edema in the mid and distal aspect of the vastus medialis and vastus lateralis muscles. A biopsy of the left quadriceps muscles was diagnostic of inclusion body myositis. He remained asymptomatic for the ensuing 2.5 years.

CONCLUSIONS

Asymptomatic hyperCKemia should be investigated and followed closely for definitive diagnosis and possible treatable causes.

Asymptomatic hyperCKemia during a two-year monitoring period: A case report and literature overview

High creatine kinase (CK) levels can be associated with many disorders, including neuromuscular, cardiac, metabolic, endocrine and traumatic. Idiopathic hyperCKemia is a diagnostic dilemma for physicians even though its long-term prognosis is usually benign. We report a case of a Caucasian 61-year-old woman who presented as completely asymptomatic to her general practitioner with a serum CK (sCK) level at 6,122 IU/l. A complete diagnostic evaluation, including physical and laboratory examinations, electromyogram and muscle biopsy were negative for any neuromuscular or other disorder. Two years later the patient remains asymptomatic, active and overall healthy but sCK levels remain elevated, ≤6,591 IU/l (>50-fold higher than normal values).

Approach to asymptomatic creatine kinase elevation

How to manage a patient who has an elevated serum creatine kinase (CK) level but no or insignificant muscle-related signs and symptoms is a clinical conundrum. The authors provide a systematic approach, including repeat testing after a period of rest, defining higher thresholds over which pursuing a diagnosis is worthwhile, and evaluating for a variety of nonneuromuscular causes. They also outline a workup for neuromuscular causes.

Reevaluating Muscle Biopsies in the Diagnosis of Pompe Disease: A Corroborative Report

Background: Previous reports suggest that although a diagnostic muscle biopsy can confirm the presence of Pompe disease, the absence of a definitive biopsy result does not rule out the diagnosis. Methods: In this study, we reviewed patients with a limb-girdle syndrome who demonstrated nonspecific abnormalities of muscle, without evidence of the classical changes of acid maltase deficiency. These patients were rescreened for Pompe disease using dried blood spot (DBS) testing. Results: Twenty-seven patients provided blood samples for the DBS test. Four patients underwent subsequent genetic testing. Genetic analysis demonstrated that one patient tested positive for Pompe disease and one patient had one copy of a pathogenic variant. Conclusions: In conclusion, the ability of a diagnostic muscle biopsy to definitively rule out the presence of Pompe disease is limited. There is a role for a screening DBS in all patients presenting with a limb-girdle syndrome without a clear diagnosis.

Guidelines for the diagnosis, treatment and clinical monitoring of patients with juvenile and adult Pompe disease

ABSTRACT Pompe disease (PD) is a potentially lethal illness involving irreversible muscle damage resulting from glycogen storage in muscle fiber and activation of autophagic pathways. A promising therapeutic perspective for PD is enzyme replacement therapy (ERT) with the human recombinant enzyme acid alpha-glucosidase (Myozyme®). The need to organize a diagnostic flowchart, systematize clinical follow-up, and establish new therapeutic recommendations has become vital, as ERT ensures greater patient longevity. A task force of experienced clinicians outlined a protocol for diagnosis, monitoring, treatment, genetic counseling, and rehabilitation for PD patients. The study was conducted under the coordination of REBREPOM, the Brazilian Network for Studies of PD. The meeting of these experts took place in October 2013, at L’Hotel Port Bay in São Paulo, Brazil. In August 2014, the text was reassessed and updated. Given the rarity of PD and limited high-impact publications, experts submitted their views.

Milder forms of muscular dystrophy associated with POMGNT2 mutations

Objective:

To determine the genetic variants in patients with dystroglycanopathy (DGP) and assess the pathogenicity of these variants.

Methods:

A total of 20 patients with DGP were identified by immunohistochemistry or Western blot analysis. Whole-exome sequencing (WES) was performed using patient samples. The pathogenicity of the variants identified was evaluated on the basis of the phenotypic recovery in a knockout (KO) haploid human cell line by transfection with mutated POMGNT2 cDNA and on the basis of the in vitro enzymatic activity of mutated proteins.

Results:

WES identified homozygous and compound heterozygous missense variants in POMGNT2 in 3 patients with the milder limb-girdle muscular dystrophy (LGMD) and intellectual disability without brain malformation. The 2 identified variants were located in the putative glycosyltransferase domain of POMGNT2, which affected its enzymatic activity. Mutated POMGNT2 cDNAs failed to rescue the phenotype of POMGNT2-KO cells.

Conclusions:

Novel variants in POMGNT2 are associated with milder forms of LGMD. The findings of this study expand the clinical and pathologic spectrum of DGP associated with POMGNT2 variants from the severest Walker-Warburg syndrome to the mildest LGMD phenotypes. The simple method to verify pathogenesis of variants may allow researchers to evaluate any variants present in all of the known causative genes and the variants in novel candidate genes to detect DGPs, particularly without using patients' specimens.

A Neuromuscular Approach to Statin-Related Myotoxicity

Approximately 95% of statin-treated patients tolerate this form of cholesterol management without any adverse effects. However, given their efficacy in reducing low density lipoproteins and cardiovascular events large numbers of patients are selected for statin therapy. Therefore muscle complications are, in fact, quite common. Limited understanding of the underlying pathophysiology has hampered physicians' ability to identify patients at risk for developing statin myotoxicity. A growing number of published case reports/series have implicated statins in the exacerbation of both acquired and genetic myopathies. A clinical management algorithm is presented which outlines a variety of co-morbidities which can potentiate the adverse effects of statins on muscle. In addition, a rational approach to the selection of those patients most likely to benefit from skeletal muscle biopsy is discussed. Ongoing work will define the extent to which statin-intolerant patients represent carriers of recessive metabolic myopathies or pre-symptomatic acquired myopathies. The expanding importance of pharmacogenomics will undoubtedly be realized in the field of statin myopathy research within the next few years. Such critical information is needed to establish more definitive management and diagnostic strategies.

Hyponatraemia induced hyperCKaemia

A 32-year-old woman presented to Kasturba Hospital, Manipal with the features of gastroenteritis and one episode of generalised tonic clonic seizure with loss of consciousness for 5 min. No abnormalities were found during neurological examination. Her baseline investigations showed low sodium, low serum osmolality, normal renal and liver function tests, urine myoglobin and antinuclear antibodies profile were negative. Incidentally her creatine kinase (CK) levels were found to be very high. She was treated with intravenous fluids and high salt diet for hyponatraemia. With correction of hyponatraemia, CK levels also improved, suggesting the probable diagnosis of hyponatraemia induced myopathy leading to hyperCKaemia. The importance of early recognition of this potentially-dangerous and rare condition is emphasised.

Screening for later-onset Pompe's disease in patients with paucisymptomatic hyperCKemia

BACKGROUND

Pompe's disease is an inherited metabolic myopathy caused by acid α-glucosidase deficiency. Early diagnosis optimizes the treatment effectiveness.

METHODS

One-hundred-thirty-seven consecutive patients with unexplained hyperCKemia underwent the assessment of acid α-glucosidase activity on dried blood spot. Second tier confirmatory testing in positive patients included the assessment of α-glucosidase activity on lymphocytes or muscle tissue and molecular analysis.

RESULTS

Three patients were diagnosed with later-onset Pompe's disease, revealing 2.2% prevalence in asymptomatic hyperCKemia. Moreover, three patients positive to the screening revealed abnormal biochemical second tier testing, but were heterozygous for the common c.-32-13T>G mutation at molecular level.

CONCLUSIONS

The selective screening for later-onset Pompe's disease in asymptomatic hyperCKemia allowed the identification of affected patients in a pre-clinical stage. Additionally, the identification of carriers with biochemical alterations related to Pompe's disease extends the spectrum of its manifestations to heterozygous subjects.

Screening test for malignant hyperthermia in patients with persistent hyperCKemia: a pilot study

INTRODUCTION

Persistently elevated serum creatine kinase (CK) is frequently associated with predisposition to malignant hyperthermia (MH). We investigated whether a minimally invasive metabolic test is suitable to diagnose MH susceptibility among patients with hyperCKemia.

METHODS

Thirty-nine participants were included: 10 were MH susceptible (MHS); 21 MH were non-susceptible (MHN); and 8 had MHN with persistent hyperCKemia >500 U/L. Microdialysis probes were inserted into the vastus lateralis muscle, and halothane or caffeine was injected via an attached microtubing catheter. Lactate concentrations in dialysis samples were measured spectrophotometrically.

RESULTS

Baseline lactate did not differ between the groups. After local application of halothane or caffeine, a significant lactate increase was detected only in the MHS group.

CONCLUSIONS

Test results were not influenced by hyperCKemia. To avoid risks and complications of a surgical muscle biopsy this microdialysis test might be a useful screening tool for MH susceptibility among patients with persistent CK elevation.

Exertional rhabdomyolysis: a clinical review with a focus on genetic influences

In this review, the clinical and laboratory features of exertional rhabdomyolysis (ER) are discussed in detail, emphasizing the full clinical spectrum from physiological elevations of serum creatine kinase after exertion to life-threatening rhabdomyolysis with acute kidney injury and associated systemic complications. Laboratory markers used to diagnose both ER and rhabdomyolysis are very sensitive, but not very specific, and imperfectly distinguish "subclinical" or asymptomatic from severe, life-threatening illness. However, genetic factors, both recognized and yet to be discovered, likely influence this diverse clinical spectrum of disease and response to exercise. Genetic mutations causative for McArdle disease, carnitine palmitoyl transferase deficiency 2, myoadenylate deaminase deficiency, and malignant hyperthermia have all been associated with ER. Polymorphic variations in the myosin light chain kinase, α-actin 3, creatine kinase-muscle isoform, angiotensin I-converting enzyme, heat shock protein, and interleukin-6 genes have also been associated with either ER or exercise-induced serum creatine kinase elevations typical of ER. The prognosis for ER is significantly better than that for other etiologies of rhabdomyolysis, but the risk of recurrence after an initial episode is unknown. Guidelines for management are provided.

[Elevated plasma creatine kinase activity - does it always indicate muscle disease?]

Despite advanced diagnostic procedures in muscle disorders, creatine kinase (CK) activity is still one of the parameters most often investigated in serum. It is used mainly in neuromyology, and helps to differentiate between myogenic and neurogenic processes. Furthermore, it is applied to monitor the course of the disease and treatment results. Occasionally, marked elevated CK activity requires detailed diagnostic work-up, including electrophysiological, histopathological and genetic studies. In some cases, it enables the final diagnosis to be established. However, there is still a group of patients with so-called idiopathic hyper-CKemia and with no evidence of neuromuscular disorder. As little is known about potentially asymptomatic hyper-CK-emia, these patients should be carefully monitored.

Transient creatine phosphokinase elevations in children: a single-center experience

OBJECTIVES

To determine the etiologies and evolution of rhabdomyolysis in children.

STUDY DESIGN

We performed a retrospective study of patients with rhabdomyolysis who were seen in our tertiary care university-affiliated pediatric hospital. Patients in outpatient clinics, seen in the emergency department, or admitted from 2001 to 2002 were selected. With a standardized case report form, we collected predetermined data from each patient's chart.

RESULTS

A total of 130 patients with rhabdomyolysis were included in the study (male, 56%; mean age, 7.5 ± 5.9 years). The median elevation of creatine phosphokinase was 2207 IU/L (range, 1003 to 811 428 IU/L). The most frequent diagnoses were viral myositis (29, 22.3%), trauma (24, 18.4%), surgery (24, 18.4%), hypoxia (12 , 9.2%), and drug reaction (8, 6.2%). Metabolic myopathy was found only in one patient (0.8%). In 17 patients (13.1%), no definite diagnosis could be made.

CONCLUSIONS

Etiologies of rhabdomyolysis in children are varied and differ from those reported in adults. In most patients, rhabdomyolysis is benign and without recurrence. In our series, rhabdomyolysis was the initial symptom of a metabolic myopathy in only one patient.

Variation of serum creatine kinase (CK) levels and prevalence of persistent hyperCKemia in a Norwegian normal population. The Tromsø Study

In this cross-sectional study we assessed the prevalence of hyperCKemia, defined as persistent CK values ≥210 U/L in women, ≥400 U/L in men <50 years and ≥280 U/L in men ≥50 years (reference values according to the Nordic Reference Interval Project). Blood samples were obtained from 12,828 participants in the 6th survey of The Tromsø Study. We identified 686 (5.3%) individuals with incidentally elevated CK. After a standardized control test, 169 persons (1.3%) had persistent hyperCKemia, i.e. 69.9% normalization. Use of statins or other causes of hyperCKemia were detected in 78 individuals (46.2%), giving a prevalence of "idiopathic hyperCKemia" of 0.71%. CK variation was highest in younger men and in females between 60 and 69 years. This study has identified persistent hyperCKemia in 1.3% of the normal population, and demonstrates the importance of performing controlled CK analyses, also in those with identified risk factors.

Diagnostic criteria for late-onset (childhood and adult) Pompe disease

The diagnosis of late-onset (childhood and adult) Pompe disease can often be challenging, as it is a rare disease and the heterogeneous clinical presentation can mimic the presentation of other neuromuscular disorders. The objective was to develop a consensus-based algorithm for the diagnosis of late-onset Pompe disease. A systematic literature search was conducted, and an expert panel composed of neuromuscular specialists and individuals with expertise in Pompe disease reviewed the literature and convened for consensus development. An algorithm for the diagnosis of late-onset Pompe disease was created. Patients presenting with either a limb-girdle syndrome or dyspnea secondary to diaphragm weakness should undergo further testing, including evaluations of muscle strength, motor function, and pulmonary function. A blood-based acid alpha-glucosidase (GAA) enzyme activity assay is the recommended tool to screen for GAA enzyme deficiency. The diagnosis should be confirmed by a second test: either a second GAA enzyme activity assay in another tissue or GAA gene sequencing.

[McArdle disease (gycogenosis type V): analysis of clinical, biological and genetic features of five French patients]

INTRODUCTION

McArdle disease (glycogenosis type V) is an autosomal recessive metabolic myopathy. Defect in glycogen breakdown is due to mutations of the gene for myophosphorylase (PYGM). Among patients of the department, we searched for correlations between disease phenotype, biochemistry analysis of muscle samples and PYGM genotype.

METHODS

We included five patients whose muscle biopsy showed deposits of glycogen and negative histochemical staining for myophosphorylase.

RESULTS

All patients exhibited exercise intolerance and high serum CK levels (mean 4400). Two of them had an acute renal insufficiency caused by rhabdomyolysis. One patient developed moderate late-onset muscle weakness of the proximal part of upper limbs. Muscle glycogen concentration was high (three times the normal). Myophosphorylase activity was undetectable in four muscle samples out of five. Two patients were homozygous and two other heterozygous for the R50X mutation of PYGM. The other one had a novel missense mutation S814N. Patients homozygous for R50X mutation had higher CK levels (8080 versus 1457, p=0.046), but disease severity and muscle glycogen concentrations were equivalent.

CONCLUSIONS

Our patients had typical clinical and laboratory features of McArdle disease. Diagnosis was suggested by exercise intolerance with high CK levels. The R50X mutation was the most common (60% of the mutated alleles). We found no relationship between clinical severity, PYGM genotype and biochemistry analysis of muscle samples.