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Ten adult patients complained of exercise intolerance;five of them had cramps and three had recurrent myoglobinuria.Resting serum CK was increased in five.Muscle biopsies showed phosphorylase b kinase(PbK) deficiency,whereas the activities of other enzymes of carbohydrate metabolism were normal.None of the patients exhibited symptoms indicative of liver PbK deficiency.Thus,these patients are new additions to a class of PbK glycogen storage disease characterized by enzyme deficiency in muscle but not liver.Family histories were consistent with autosomal recessive transmission.Monoclonal antibodies specific for the B and y subunits of PbK cross-reacted differentially with muscle biopsies from three of these patients,suggesting that this phenotype of PbK deficiency is biochemically heterogeneous. |
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