The disease predominates among people of Askenazi Jewish descent (probably due to a founder effect) and is most commonly due to the Y329S mutation in GBE1. Not too surprisingly, this is a “mild” mutation, which probably explains the late onset of symptoms. Thanks to the energy and compassion of one patient, Gregory Weiss, a research foundation (APBDRF; www.apbdrf.org) has been created to develop Inhibitors,research,lifescience,medical therapeutic strategies. GSD V (myophosphorylase deficiency, McArdle disease) The clinical picture and the block in muscle
glycogen breakdown were elegantly described by Brian McArdle in 1951 (35), the enzyme defects was discovered 8 years later (36-38), and it took 12 more years before the first mutations in PYGM were identified (39). Inhibitors,research,lifescience,medical Despite
its long history, McArdle disease still presents several riddles. First, although it was long considered a clinically homogeneous disease, its expression can vary from relatively mild exercise intolerance to a crippling Belinostat condition with frequent cramps and recurrent episodes of myoglobinuria. Explanations have ranged from rare cases Inhibitors,research,lifescience,medical of “double trouble” (i.e. the coexistence in the same individuals of one mutation in PYGM and another in the gene encoding adenylate deaminase) to the association with insertion/deletion polymorphisms in the
angiotensinconverting enzyme (ACE) (40). Probably more important is the protecting effect of even small Inhibitors,research,lifescience,medical amounts of myophosphorylase residual activity, which is determined by the type of mutations: for example, splice mutations are associated to milder clinical phenotypes (41). What remains unexplained is the fatal infantile form Inhibitors,research,lifescience,medical of McArdle disease, which has been reported in a handful of cases (42-45). In these unfortunate infants muscle morphology, biochemistry, and molecular genetics [showing the "common" R50X null mutation (39, 45)] are no different from typical McArdle patients, despite the dismal outcome. GSD VII (phosphofructokinase found [PFK] deficiency, Tarui disease) PFK is a tetrameric enzyme under the control of three autosomal genes: PFKM encodes the muscle subunit, PFKL encodes the liver subunit, and PFKP encodes the platelet subunit. Mature human muscle expresses only the M subunit and contains exclusively the M4 homotetramer, whereas erythrocytes, which express both the M and the L subunit, contain five isozymes, the two M4 and L4 homotetramers and three hybrid forms. In patients with typical PFK deficiency, mutations in PFKM cause total lack of activity in muscle but only partial deficiency in red blood cells.