Peripheral nerve and vasculature involvement in myophosphorylase deficiency (McArdle's disease)

Dilative arteriopathy in metabolic myopathies, particularly Pompe's disease

There is increasing evidence that some metabolic myopathies are associated with dilative arteriopathy. This review aimed at summarizing recent findings concerning the pathogenesis, presentation, diagnosis and treatment of dilative arteriopathies in patients with metabolic myopathies. Dilative arteriopathy manifests as ectasia or aneurysms. Dilative arteriopathy most frequently occurs in patients with Pompe's disease. More rarely, dilative arteriopathy occurs in other glycogenoses or mitochondrial disorders. Complications of dilative arteriopathy may be intracerebral or subarachnoid bleeding, dissection of the arterial wall or ischemic stroke. Because of the often fatal complications, patients at risk for developing dilative arteriopathy should be screened for it as soon as the diagnosis of a metabolic myopathy has been established. Dilative arteriopathy is a phenotypic feature, particularly of Pompe's disease. Early recognition of ectasias and aneurysms and appropriate interventions by enzyme replacement therapy, stenting, coiling or surgery may prevent mild or severe cerebrovascular complications or even death in some of these patients.

Muscular glycogen storage diseases without increased glycogen content on histopathological examination

Histopathological findings of muscle biopsies from five patients with two different muscular glycogen storage diseases (mGSD) were presented. From these investigations it emerged that the yield of histopathology in mGSD is low. In only one of five patients histopathological findings gave a clue towards diagnosis. It can be concluded that non-specific findings or even normal appearance of a muscle biopsy does not exclude mGSD.

Myophosphorylase deficiency affects muscle mitochondrial respiration as shown by 31P-MR spectroscopy in a case with associated multifocal encephalopathy

We report here a glycogen storage myopathy type V associated with multifocal encephalopathy. The patient, a 43-year-old male with increased serum CK, a heavy drinker and smoker, had been affected by generalized epilepsy since age 24, after a cranial injury. He had had a right hemiparesis 2 years before coming to our observation and a transient left hemiparesis the following year. CT and MRI of the brain showed multiple hemispheric lesions consistent with an ischemic process, as suggested by single photon emission tomography of the brain. Muscle biopsy showed a vacuolar myopathy, and myophosphorylase activity was 13% of the normal mean. Phosphorus magnetic resonance spectroscopy (31P-MRS) performed on resting calf muscles showed increased PCr to ATP and decreased PCr to P(i) ratios. During both aerobic and ischemic exercise 31P-MRS failed to show any cytosolic acidification and phosphomonoesters (PME) accumulation, two MRS findings in agreement with McArdle's syndrome diagnosis. Mitochondrial respiration was also affected as shown by a low PCr to P(i) ratio at rest and by a low rate of PCr re-synthesis during recovery from aerobic exercise. This latter finding in McArdle's disease can be explained by decreased mitochondrial substrate availability, which in turn can contribute to the phenotypic manifestations of the disease.