Molecular genetic study of myophosphorylase deficiency (McArdle's disease) in two Yemenite-Jewish families

Using direct sequencing and restriction fragment length polymorphism analysis, we identified two novel mutations in two unrelated Yemenite-Jewish families with typical symptoms of McArdle's disease. In one family, both father and daughter were affected, an example of pseudo-dominant transmission. The daughter was a compound heterozygote for a new nonsense mutation (R207X) and a new missense mutation (R602Q) while her father was homozygous for the R207X mutation. The mother carried only the R602Q mutation and was an asymptomatic heterozygote. In the second family, the only affected member was homozygous for the R207X mutation. This first molecular genetic study of McArdle's disease in Yemenite-Jewish patients expands the already remarkable genetic heterogeneity of McArdle's disease and suggests the existence of ethnic or private mutations within this group.     

McArdle's disease and gout.

We report the first case of McArdle's disease (muscle phosphorylase deficiency) and tophaceous gout. To examine the contribution of adenine nucleotide degradation to the disturbance of uric acid metabolism, we labeled the adenine nucleotide pool with [8-14C]adenine, and measured plasma and urine purines following vigorous exercise tests. Plasma and urinary hypoxanthine and xanthine concentrations and the specific radioactivity of urinary purines increased markedly, but plasma urate levels and uric acid excretion were not substantially modified. We suggest that, in this patient, the association of McArcle's disease with gout is coincidental.     

McArdle's disease: two clinical expressions in the same pedigree

Summary Two patients with McArdle's disease within the same pedigree and with two different clinical forms are presented. The first patient suffered from progressive muscle weakness and atrophy. Muscle morphology was that of myopathy. Residual activity of phosphorylase was 28% and sodium dodecyl sulphate electrophoresis showed decreased protein. The second case was typical of McArdle's disease, clinically and biochemically. It was concluded that the first patient was a heterozygote (residual activity 28% of normal) and the second was a homozygote, the genetic transmission being autosomal recessive.     

Molecular heterogeneity of myophosphorylase deficiency (McArdle's disease): a genotype-phenotype correlation study.

We report on 54 Spanish patients with McArdle's disease from 40 unrelated families. Molecular analysis revealed that the most common R49X mutation was present in 70% of patients and 55% of alleles. The G204S mutation was less frequent and found in 14.8% of patients and 9% of mutant alleles. The W797R mutation was observed in 16.5% of patients, accounting for 13.7% of mutant alleles. Moreover, 78% of mutant alleles among Spanish patients can be identified by using polymerase chain reaction-restriction fragment length polymorphism analysis for the R49X, G204S, and W797R mutations, which makes noninvasive diagnosis possible through molecular genetic analysis of blood DNA. Six novel mutations were found. Three were missense mutations, E348K, R601W, and A703V; two nonsense mutations, E124X and Q754X; and one single base pair deletion, 533 delA. No clear genotype-phenotype correlation emerges from our study. Most of the mutations of uncharged and solvent inaccessible residues and the truncations must disrupt the basic structure of the protein. The mutations of charged residues would be expected to interfere with internal hydrogen bonding networks, introducing severe incompatible partnering that is caused by poor packing or electrostatic repulsions.     

McArdle's disease in two generations: autosomal recessive transmission with manifesting heterozygote

A 17-year-old boy had exercise-induced cramps and myoglobinuria. The mother had myalgia and weakness after exercise but the father was asymptomatic. Muscle biopsy was normal in the father but showed glycogen storage and absent or markedly decreased histochemical stain for phosphorylase in mother and son. Autosomal dominant McArdle's disease was considered likely, but biochemical studies showed that muscle phosphorylase activity was 0.6% of normal in the son, 20% in the mother, and 45% in the father, with corresponding decreases of cross-reacting material by immunotitration. These data suggest autosomal recessive transmission. One of the parents was clinically silent and the other was a manifesting heterozygote.     

Myophosphorylase gene transfer in McArdle's disease myoblasts in vitro.

McArdle's disease is due to a genetic deficiency of glycogen phosphorylase and results in a lack of glucose mobilization from glycogen during anaerobic exercise. A genetic defect in Merino sheep produces a similar picture. We constructed a first-generation adenoviral recombinant containing the full-length human phosphorylase cDNA under the control of the Rous sarcoma virus promoter. Primary myoblast cultures from phosphorylase-deficient human and sheep muscle were efficiently transduced with this vector, resulting in restoration of the phosphorylase activity. A similar correction of the genetic defect in muscles of McArdle's patients in vivo appears feasible, preferably with the use of an adeno-associated viral vector.     

Myofibrillar activation failure in McArdle's disease

Contractile properties of the adductor pollicis muscle were examined in 9 normal volunteers and 7 patients with histochemically proven myophosphorylase deficiency (McArdle's disease). Fatiguing contractions were produced by supramaximal stimulation of the ulnar nerve, delivered over a range of frequencies, to allow further examination of the mechanisms responsible for the premature fatigue in patients. The excessive reductions in force, demonstrated in patients at all frequencies, were not associated at high frequencies (50 and 100 Hz) with excessive declines in excitation (measured as compound muscle action potential). These results demonstrate that, in patients, myofibrillar activation failure occurs over and above that due to excitation failure. Abnormal slowing of relaxation mechanisms was also confirmed. These findings appear consistent with the hypothesis of inhibition of various ATPases by metabolic products. The observed, clear differences between normal subjects and myophosphorylase-deficient patients constitute the basis of an objective screening procedure for this and other glycolytic disorders.     

Early-onset Alzheimer's disease in 2 large Belgian families

Familial Alzheimer's disease (FAD) is a dominantly inherited condition that may present with an early onset, and myoclonus occurs frequently in the course of the disease. We report clinical and neuropathologic data on 2 large Belgian families with FAD in which we obtained 17 autopsies of the CNS. In family A, each of 11 autopsies had the typical neuropathologic features of Alzheimer's disease (AD), and there were a few cerebellar plaques in the molecular layer. In family B, in addition to the typical characteristics of AD in 6 autopsies, there were numerous amyloid plaques in the cortical cerebellar layers. In both families, we immunostained the amyloid deposits for the A4 protein, and they were negative for prion-associated protein immunoreactivity.     

Molecular and clinical study of McArdle's disease in a cohort of 123 European patients. Identification of 20 novel mutations

McArdle's disease is the most common muscle glycogenosis. It is caused by the deficiency of myophosphorylase, encoded by the PYGM gene. We studied 123 patients previously diagnosed with McArdle's disease and we identified 20 novel mutations (10 missense and 3 nonsense mutations, 3 small deletions, 2 gross deletions and 2 small insertions). Most patients of this cohort belong to Spanish and French populations. This allowed us to determine the differences between the allelic frequencies of the common mutations R50X and G205S of these populations. The R50X has an allelic frequency in this cohort of about 61.7%, being 68.5% in French and 53.7% in Spanish patients. The G205S had a higher allelic frequency in the Spanish (10.2%) than in the French population (3.2%). Moreover, a clinical study of 91 patients was performed to establish both genotype-phenotype correlation and gender influence in the severity of the disease. We conclude that no genotype-phenotype correlation is evident and that no gender effect is related to the phenotype.     

Exercise tolerance and daily life in McArdle's disease

McArdle's disease is a common disorder of muscle metabolism and is due to myophosphorylase deficiency. The major complaint of patients with this disease is effort intolerance. Although the clinical features of affected patients are well known, their daily lifestyle is not well documented. The main objective of this work was to assess their mean daily energy expenditure (DEE) and compare it with control subjects. Thirty patients and 87 control subjects completed a questionnaire. A 3-day self-record of daily physical activities was used to estimate the mean DEE for patients and control subjects. A separate section of the questionnaire was used to assess patients' clinical features and daily lifestyle. The DEE of patients (44.1 +/- 6.9 kcal/kg) was not significantly different from control subjects (44.5 +/- 5.6 kcal/kg). Half of the patients with McArdle's disease performed a daily physical leisure activity as sport, sometimes at a high level (17%). Despite large individual variation, physical abilities and patients' symptoms were negatively correlated. Physical leisure activity significantly decreased the sensation of muscle pain (P < 0.03). These findings show that patients with McArdle's disease do not have a strictly sedentary lifestyle. Moreover, physical exercise appears to have positive effects on the main clinical features, such as effort intolerance. Thus, regular, moderate physical activity may be beneficial in McArdle's disease.     

Huntington病两家系基因分析

目的 建立准确而快速的IT15基因胞嘧啶-腺嘌呤-鸟嘌呤(CAG)重复序列检测方法,并应用于Huntington病患者的基因诊断及症状前诊断.方法 应用聚合酶链反应、聚丙烯酰胺凝胶电泳及DNA测序技术对Huntington病两家系中的15名成员进行IT15基因CAG重复数目的检测及分析.结果 两家系中共计检出8名成员携带异常的IT15基因,其中2例先证者CAG重复序列存在异常扩增,1例(AⅡ4)出现Huntington病临床表现,其余5例尚未出现Huntington病临床症状与体征.结论 IT15基因CAG重复序列的异常扩增是Huntington病的发病基础,应用上述检测方法对IT15基因CAG重复序列进行检测可对Huntington病患者进行准确的基因诊断及症状前诊断.     

Anderson-Fabry disease with cerebrovascular complications in two Italian families

We describe four patients with cerebrovascular complications from two unrelated Italian families with Anderson-Fabry disease. Clinical examination, neuroimaging (MRI), biochemical and genetic analyses were carried out in all the patients. α-Galactosidase A activity was detected by fluorimetric assay and genetic analysis was performed by DNA sequencing. Family 1. A male patient presented recurrent strokes when he was 34 years old, albuminuria and subsequently progressive renal failure to renal transplantation. Family 2. A male patient, aged 32 years, had diplopia for a few days and then recurrent strokes with left spastic hemiparesis and internuclear ophthalmoplegia. A female patient, aged 48 years, presented L-dopa-responsive parkinsonism, and her sister had stroke when she was 55 years old. MRI was abnormal in all the patients and showed lacunar infarctions in the periventricular white matter, basal ganglia and pons. Lesions were detected by MRI even before stroke in a female patients. In patients with Anderson-Fabry disease, stroke is a frequent complication, and may be the first threatening clinical manifestation. In young people with undefined stroke, even without signs of renal involvement, it is important to consider the diagnosis of Anderson-Fabry disease and so to perform clinical examination and biochemical analyses. The pre-clinical stage of cerebrovascular involvement may be evaluable by MRI. Received: 10 November 2001 / Accepted in revised form: 15 March 2002     

Impairment of muscle mitochondrial oxidative metabolism in McArdle's disease

Impairment of muscle glycogenolysis in McArdle's disease (myophosphorylase deficiency) leads to exercise intolerance and exercise-induced myalgia. The pathophysiology of these symptoms is not entirely clear. We used phosphorus magnetic resonance spectroscopy to measure muscle phosphate metabolite concentrations and intracellular pH during brief ischemic exercise and in the period of aerobic metabolic recovery after exercise, with special attention to cytoplasmic adenosine 5′-diphosphate (ADP). In 5 patients with McArdle's disease, calculated muscle intracellular ADP concentrations at the beginning of recovery were higher than in normal control subjects (70–425 mmol/L, control mean: 73 ± 40 mmol/L, P < 0.05). The half-time for intracellular ADP recovery after exercise, an index of maximal mitochondrial oxidative phosphorylation, was 0.16 ± 0.07 in normal controls and was independent of metabolic state or intracellular pH. ADP recoveries were abnormally slow in all patients with McArdle's disease (range: 0.32–0.83 min, mean = 0.2 min, P < 0.0001). These results are indicative of a limitation in the rate of oxidative phosphorylation in muscle of patients with McArdle's disease, most likely due to impaired substrate delivery to mitochondria. This impairment of mitochondrial function may contribute to the exercise-related symptoms in McArdle's disease. © 1996 John Wiley & Sons, Inc.     

Myophosphorylase deficiency (McArdle's disease): report of a family.

The clinical and biochemical findings are presented of two brothers suffering from McArdle's Disease (Myophosphorylase Deficiency). Tissue enzyme estimations and lactate levels were done in affected and non-affected members of the family. Affected members showed absence of phosphorylase enzyme by histochemical and quantitative estimation. No quantitative abnormalities were found in other enzyme systems of glycolytic pathways in the family investigated. Various other aspects of clinical features, biochemical abnormalities and inheritance are discussed.