[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).
Flavier
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Service central de physiologie clinique, Unité d'exploration métabolique (CERAMM), Hôpital Lapeyronie, CHU de Montpellier et Inserm, équipe ERI 25 / EA 4202 Muscle et pathologies, Montpellier.
Rolland
M O
MO
Eude
M
M
Fédou
C
C
Brun
J F
JF
Maire
I
I
Mercier
J
J
Raynaud
E
E
D003402:Creatine Kinase / Q000097:blood; D005080:Exercise Test; D005260:Female; D006003:Glycogen / Q000378:metabolism; D024982:Glycogen Phosphorylase, Muscle Form / Q000235:genetics; D006012:Glycogen Storage Disease Type V / Q000175:diagnosis* / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D006005:Phosphorylases / Q000032:analysis; D011659:Pulmonary Gas Exchange
D019344:Lactic Acid; D006003:Glycogen; D024982:Glycogen Phosphorylase, Muscle Form; D006005:Phosphorylases; D003402:Creatine Kinase