Glycogenosis type 5
Overview
Summary: McArdle’s disease is resulted from the deficiency of the muscle isoform of glycogen phosphorylase (myophosphorylase). This is the first myopathy in which a single enzyme defect was demonstrated. It is also entirely restricted to muscle. Other than the fatal infantile form, McArdle’s disease is compatible with long-term survival. It is classically associated with life long exercise intolerance. The initial symptoms are mild and patient may be carrying a label of “lazyness”. Later symptoms include muscle cramps after exercise, myoglobinuria, and, in later course of the disease, muscle wasting. Severe sternous exercise may cause myoglobinuria that is severe enough to cause acute renal failure. In the past, many cases are not diagnosed until adulthood. Histologically, there is an increased storage of glycogen and absence of phosphorylase activity. The presence of abundance of necrotic and regenerating fibers could qualify this disease as a muscular dystrophy. The biochemical structure of the stored glycogen is normal.
Symptoms
* Muscle cramps after exercise * Myoglobin in urine * Reduced muscle phosphorylase activity * Absent muscle phosphorylase activity
Treatment
Treatment of glycogenosis type V with ketogenic diet Verena Busch, MD 1, Klaus Gempel, MD 2, Alexandra Hack 1, Klaus Müller, PhD 3, Matthias Vorgerd, MD 3, Hanns Lochmüller, MD 4, Friedrich A. M. Baumeister, MD 1 1Department of Pediatrics and Children's Hospital Medical Center, Munich University of Technology, Munich, Germany 2Institute for Clinical Chemistry, Molecular Diagnostics and Mitochondrial Genetics and Munich Metabolic Disease Centre at the Academic Hospital Schwabing, Munich, Germany 3Department of Neurology, Kliniken Bergmannsheil, Neuromuscular Center Ruhrgebiet, Bochum, Germany 4Department of Neurology, Friedrich-Baur-Institut and Gene Center, Klinikum der Universität-Innenstadt, Ludwig Maximilian University, Munich, Germany