The significance of clinical and laboratory features in the diagnosis of glycogen storage disease type v: a case report

Glycogen storage disease type V (GSD-V) is the most common disorder of muscle glycogenosis with characteristic clinical and laboratory findings. A 32-yr-old woman complained of exercise intolerance and myoglobulinuria since early adolescence. She reported several episodes of second-wind phenomenon. Physical examination did not show any neurological abnormality, including fixed muscle weakness or atrophy. Serum creatine kinase level was 1,161 IU/L at rest. The result of the non-ischemic forearm exercise test was compatible with GSD-V. Mutation analysis identified the compound heterozygous mutations of the PYGM, p.D510fs and p.F710del, which has not yet been reported in Korea. The present case recognizes that detail clinical and laboratory analysis is the first step in the diagnosis of GSD-V.

McArdle's disease: a clinical review and case report

McArdle's Disease is a rare glycogen disease involving deficiency in muscle phosphorylase. This deficiency can lead to rhabdomyolysis and subsequently renal failure. McArdle's Disease has a similar presentation as several other metabolic myopathies with exercise-induced fatigue, myalgias, weakness or unexplained rhabdomyolysis. Suspicion should be raised in the presence of unexplained symptoms, and muscle biopsy can be done to confirm the diagnosis.

[A case of acute renal failure secondary to late-onset McArdle's disease]

INTRODUCTION

Mc Ardles disease, also known as Type V glycogen storage disease, is a rare deficiency of the enzyme glycogen phosphorylase in muscle cells, inherited as an autosomal recessive trait. In the absence of this enzyme, muscles cannot break down glycogen during exercise, so in patients affected by McArdles disease even moderate physical activity produces cramps, pain and fatigue. Anaerobic activity leads to severe fixed contractures and rhabdomyolisis with myoglobinuria and raised serum creatine-kinase, which, in turn, can lead to acute renal failure. Disease onset is usually in early childhood, although diagnosis is often not made until the second or third decade.

CASE REPORT

We present the case of a 68-year-old man who presented to the Emergency Room with fatigue, vertigo, diarrhea and oliguria. The patient underwent five daily hemodialysis sessions, diuresis reappeared and there was progressive recovery of renal function. The patient described episodes of fatigue and muscular pain occurring since childhood: the positive personal history, together with persistently raised CPK levels in the absence of any infective or toxic cause of myositis, led us to suspect the presence of this rare metabolic disease, which was subsequently confirmed by muscle biopsy.

CONCLUSION

To date, there is no specific treatment for type V glycogenosis, although a diet rich in protein and saccarose, vitamin B6 supplementation and creatine administration are generally recommended. Moderate physical activity can help manage symptoms by improving exercise tolerance and blood supply to the muscles, ensuring provision of glucose and free fatty acids for the muscle fibers.

Exercise induced fatigue: unfit or unwell?

This case report outlines the diagnoses of a rare myophosphorylase deficiency (McArdle Syndrome) in a unique way. A set of characteristic values from a Cardiopulmonary Exercise Test (CPET) combined with a typical patient history pointed to a failure of the glycolytic pathway in the skeletal muscle. McArdle Syndrome was confirmed with a skeletal muscle biopsy. There is no evidence of such a diagnostic method in the literature.

[Myalgia during warming-up in a 12-year-old boy]

INTRODUCTION

McArdle disease is a hereditary myopathy caused by muscle phosphorylase deficiency. Patients experience painful muscle cramps after strenuous exercise; the condition is sometimes associated with rhabdomyolysis, myoglobinuria and resulting acute renal failure.

CASE DESCRIPTION

A 12-year-old boy visited the Paediatric and Neurology outpatients' departments with symptoms of leg myalgia, occurring during the warming-up phase of soccer practice, which disappeared after a short rest. Detailed history-taking revealed that he already experienced pain while walking during early childhood. An elevated serum creatine kinase concentration in combination with the typical presentation led to the presumptive diagnosis 'McArdle disease', which was confirmed by molecular genetic analysis.

CONCLUSION

There is no effective gene therapy; a multidisciplinary approach by a neurologist, paediatrician, physiotherapist and nutritionist is advised.

A case of McArdle disease: efficacy of vitamin B6 on fatigability and impaired glycogenolysis

McArdle disease is a glycogenetic myopathy caused by a deficit of myophosphorylase inherited in an autosomal recessive pattern. Here, we report a case of McArdle disease in which fatigability was the only subjective complaint. Objective neurological findings were normal except for very mild muscle weakness in limbs and an elevated serum creatine kinase level. Ischemic forearm exercise test showed deficient glycogenolysis. In the muscle biopsy specimen, periodic acid Schiff (PAS) stained subsarcolemmal glycogen was increased and the muscle phosphorylase A activity was decreased. After administration of vitamin B6, fatigability was diminished and ischemic forearm exercise test showed improved glycogenolysis. Vitamin B6 may be beneficial for McArdle disease, especially for its easy fatigability.

Recurrent acute kidney failure due to McArdle disease

We present an adolescent with McArdle disease and recurrent acute kidney failure due to rhabdomyolysis. The patient was admitted with acute kidney failure for 3 times and due to a history of proximal weakness, fatigue, and muscular cramps after physical activities a glycogen-storage disease was suspected. Serum creatine phosphokinase and urine myoglobin were found to be elevated. McArdle disease was diagnosed based on pathologic examination of muscle tissue specimen. Patients presenting with rhabdomyolysis following strenuous exercise should be evaluated for McArdle disease.

[Late diagnosis of a McArdle disease's case (type V glycogenosis)]

McArdle's disease is a metabolic myopathy characterized by a myophosphorylase deficiency resulting in an inability to degrade glycogen stores. We report the case of a 48 years old patient who complained since adolescence of rest and exercise myalgias and presented a chronic increased plasma creatine kinase activity. First, a maximal exercise test was performed. This test demonstrated a quasi lack of rise of respiratory exchange ratio and of blood lactate, possibly due to a glycogenolytic/glycolytic pathway deficiency. Second, a biopsy of vastus lateralis muscle was performed using Bergström needle. As expected, the analysis of mitochondrial function was normal. The in vitro screening test of the glycogenolysis/glycolysis pathway showed a lack of lactate production in presence of glycogen substrate. The study of muscular metabolism of glycogen revealed a glycogen accumulation and a decrease of active and total phosphorylase activities. These data allowed us to diagnose a type V glycogenosis, or McArdle's disease. The patient appeared heterozygous for the most frequent mutation (p.R50X).

Rhabdomyolyse massive révélant une maladie de McArdle

INTRODUCTION

McArdle's disease is an autosomal recessive glycogenosis caused by deficiency of muscle glycogen phosphorylase resulting in glycogen accumulation in the skeletal muscle. Typically, McArdle's disease is characterized by exercise intolerance with muscle cramps and myoglobinuria.

CASE REPORT

We report a 20-year-old woman with massive rhabdomyolysis and acute renal failure revealing a McArdle's disease.

DISCUSSION

Although muscle impairment is constant in McArdle's disease, massive rhabdomyolysis with severe acute renal failure has been rarely reported as a presenting feature. The mechanisms and therapeutic implications of renal injury are discussed.

McArdle disease presenting as acute renal failure

In 1951, McArdle described a glycogen storage disorder which presents primarily as a myopathy. It is characterized by muscle pain, weakness and exercise intolerance with elevated creatine kinase from rhabdomyolysis. The pathophysiology involves a deficiency of myophosphorylase enzyme resulting in an inability to degrade glycogen stores. We present a novel case of McArdle disease (glycogen storage disease V [GSDV]) in a patient who had sickle cell trait and bulimia. The disease went unrecognized despite several admissions to the hospital with increased creatine kinase and muscle myopathy until the patient's initial presentation with acute renal failure.

A proposed molecular diagnostic flowchart for myophosphorylase deficiency (McArdle disease) in blood samples from Spanish patients

McArdle disease is a metabolic myopathy due to molecular defects in the myophosphorylase gene (PYGM), usually diagnosed in muscle biopsy. The aims of this study were to characterize genetically a large series of patients and to establish a protocol of molecular diagnosis on blood samples. We studied 55 Spanish unrelated patients with McArdle disease. Screening for the three more frequent mutations in the PYGM gene in the Spanish population (c.148C>T, p.R50X; c.613G>A, p.G205S; and c.2392T>C, p.W798R) were performed with polymerase chain-reaction and restriction fragment length polymorphism (PCR-RFLP) methods. To identify other mutant alleles, the coding region of PYGM gene was sequenced. The p.R50X mutation was observed in 38 patients, the p.G205S substitution in eight, and the p.W798R change in nine. Nine novel mutations, five missense (c.247A>T, p.I83F; c.521G>A, p.G174D; c.1094C>T, p.A365V; c.1468C>T, p.R490W; and c.1730A>G, p.Q577R), one nonsense mutation (c.2352C>A, p.C784X), three frameshift (c.402del, p.N134KfsX161; c.212_218dup, p.Q73HfsX7; c.1470dup, p.R491AfsX7), and nine previously reported mutations were found. In addition, we also updated the molecular data of 95 unrelated patients with McArdle disease studied thus far in our center. Of these patients, 56 were either homozygous or compound heterozygous for the p.R50X, p.G205S, or p.W798R mutation. By including in the molecular diagnosis protocol sequencing of the exons 1, 14, 17 and 18 of the PYGM gene, 16 further patients were characterized, and therefore we were able to detect the molecular defect in 72 out of 95 patients. A proposed molecular diagnosis protocol of the disease based on blood DNA would avoid muscle biopsy in 75.8% [95% confidence interval (95% CI): 62.1%-78.6%] of patients with McArdle disease.

Impaired oxygen extraction in metabolic myopathies: Detection and quantification by near-infrared spectroscopy

Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O(2) extraction, low maximal aerobic power, and reduced exercise tolerance. Non-invasive tools are needed to quantify the metabolic impairment. Six patients with MM, 6 with McA, 25 with symptoms of metabolic myopathy but negative biopsy (patient-controls, P-CTRL) and 20 controls (CTRL) underwent an incremental cycloergometric test. Pulmonary O(2) uptake (VO(2)) and vastus lateralis oxygenation indices (by near-infrared spectroscopy, NIRS) were determined. Concentration changes of deoxygenated hemoglobin and myoglobin (Delta[deoxy(Hb + Mb)]) were considered an index of O(2) extraction. Delta[deoxy(Hb + Mb)] peak (percent limb ischemia) was lower in MM (25.3 +/- 12.0%) and McA (18.7 +/- 7.3) than in P-CTRL (62.4 +/- 3.9) and CTRL (71.3 +/- 3.9) subjects. VO(2) peak and Delta[deoxy(Hb + Mb)] peak were linearly related (r(2) = 0.83). In these patients, NIRS is a tool to detect and quantify non-invasively the metabolic impairment, which may be useful in the follow-up of patients and in the assessment of therapies and interventions.

Do carriers of PYGM mutations have symptoms of McArdle disease?

The authors investigated whether carriers of single myophosphorylase gene (PYGM) mutations have symptoms of McArdle disease. They studied the oxidative capacity and lactate responses to maximal cycle exercise in eight patients with McArdle disease, seven single PYGM mutation carriers, and 11 healthy subjects. Heterozygotes had maximal oxidative capacity and peak lactate responses identical to control subjects. Thus, carriers of single PYGM mutations are not prone to develop symptoms of McArdle disease.

Diagnostic evaluation of clinically normal subjects with chronic hyperCKemia

The authors analyzed muscle biopsy specimens of 104 patients with creatine kinase activity greater than 500 UI/L (normal 10 to 170 UI/L) without signs of muscle weakness. They achieved a definite or probable diagnosis in 55% of cases. The most frequently identified diseases were glycogen storage diseases, muscular dystrophies, and inflammatory myopathies. The probability of making a diagnosis was higher in children and when creatine kinase level was greater than 2,000 UI/L.

Neuromuscular Disorders in Clinical Practice: Case Studies

Neuromuscular disorders represent a large group of highly varied and interesting clinical disorders, many of which have major general medical manifestations. These disorders can be diagnosed largely based on the patient's history and physical examination with a little help from modern technology. Despite the outdated belief that neurologic conditions are diagnosed but rarely treatable, all cases discussed herein represent disorders for which there are extensive options and opportunities for meaningful management. These 16 brief case overviews challenge and refresh diagnostic skills and provide the framework for selected comments regarding management options.

Internal restriction sites: quality assurance aids in genotyping

Improvements to restriction fragment length polymorphism (RFLP)-based genotyping assays currently used for detection of mutations responsible for bovine ferrochelatase and myophosphorylase deficiencies, and equine hyperkalemic periodic paralysis (HYPP) are described. Reports of sporadic inhibition of restriction enzyme activity suggest a critical factor in RFLP-based genotyping assays should be assurance that restriction enzymes perform to specification with every sample. The RFLP genotyping assays that use either a mismatched recognition sequence in one or both of the oligonucleotides, or incorporate a second native site within the PCR amplicon, provide the mechanism by which efficiency of restriction enzymes can be assessed with every sample. The outcome is confirmation of the activity of the discriminating enzyme regardless of genotype.

McArdle's Disease Presenting as Unexplained Dyspnea in a Young Woman

McArdle's disease is a rare, inherited deficiency of myophosphorylase, an enzyme required for the utilization of glycogen. Patients with myophosphorylase deficiency classically present with exercise intolerance, leg pain and muscle fatigue. The case of a young woman with exertional dyspnea and leg cramps is described. Exercise testing confirmed the presence of exercise intolerance and demonstrated an accelerated heart rate response, despite the absence of an anaerobic threshold and a respiratory exchange ratio of less than 1.0. Subsequent ischemic forearm testing and muscle biopsy confirmed the diagnosis of myophosphorylase deficiency. Evaluation of lung mechanics with esophageal pressure measurements demonstrated the presence of respiratory muscle weakness and early fatiguability, suggesting that the patient's dyspnea might have been attributable to an increased respiratory effort. Dyspnea is not a classic symptom associated with myophosphorylase deficiency, although subclinical respiratory muscle impairment may be present. No previous studies have evaluated respiratory muscle function during exercise in patients with myophosphorylase deficiency.

Prueba de ejercicio con isquemia en el antebrazo. Estandarización y valor diagnóstico en la identificación de la enfermedad de McArdle

BACKGROUND AND OBJECTIVE

The forearm ischemic exercise test (FIET) with serial lactate determinations is used worldwide for the screening of McArdle's disease and other glucogenosis. Yet there is no uniformity with regard to the intensity of the work and the ischemia time. The aim of this study was to standardize the test conditions in normal people and to check its efficacy in our population.

PATIENTS AND METHOD

In a first stage, we included 9 healthy persons in whom four different conditions were applied regarding the cuff pressure and ischemia time. In a second stage, 5 previously known McArdle disease patients, 30 normal individuals and 25 patients with a diagnosis of myopathy other than glucogenosis underwent FIET with the conditions standardized in the first stage.

RESULTS

The best curve profile was obtained with a cuff pressure 20 mm Hg above systolic blood pressure and with exercise until fatigue o cramps without time limitation. With a cut-point at 200% of the basal values of ammonium and lactate, the sensitivity and specificity of FIET were 100% and 96%, respectively, for McArdle's disease. No major side effects were recorded in any case.

CONCLUSIONS

Conditions of FIET have been standardized. Taking into account the high sensitivity and specificity of the test, its use should be considered in the screening of anaerobic metabolic myopathies.