BACKGROUND: Genetic underpinnings in Parkinson\'s disease (PD) and parkinsonian syndromes are challenging, and recent discoveries regarding their genetic pathways have led to potential gene-specific treatment trials.
METHODS: We report 3 X-linked levodopa (l-dopa)-responsive parkinsonism-epilepsy syndrome cases due to a hemizygous variant in the phosphoglycerate kinase 1 (PGK1) gene. The likely pathogenic variant NM_000291.4 (PGK1):c.950G > A;p.(Gly317Asp) was identified in a hemizygous state.
METHODS: Only 8 previous cases have linked this phenotype to PGK1, a gene more commonly associated with hemolytic anemia and myopathy. The unusual association of epilepsy, psychiatric symptoms, action tremor, limb dystonia, cognitive symptoms, and l-dopa-responsive parkinsonism must draw attention to PGK1 mutations, especially because this gene is absent from most commercial hereditary parkinsonism panels.
CONCLUSIONS: This report aims to shed light on an overlooked gene that causes hereditary parkinsonian syndromes. Further research regarding genetic pathways in PD may provide a better understanding of its pathophysiology and open possibilities for new disease-modifying trials, such as SNCA, LRRK2, PRKN, PINK1, and DJ-1 genes.

Phosphoglycerate kinase (PGK) deficiency is an X-linked disorder characterized by a combination of hemolytic anemia, myopathy, and brain involvement. We herein report a Japanese man who had several episodes of rhabdomyolysis but was training strenuously to be a professional boxer. Mild hemolytic anemia was noted. The enzymatic activity of PGK was significantly reduced, and a novel missense mutation, p.S62N, was identified in the PGK1 gene. A literature review revealed only one case with a mixed hemolytic and myopathic phenotype like ours. This mild phenotype indicates the complex pathophysiology of PGK deficiency and suggests the benefits of dietary control and exercise.

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In this review hereditary disorders of muscle metabolism are summarized. Defects in the glycogen metabolism, the glycolysis, the carnitine metabolism, the respiratory chain in the mitochondria and other rare defects are discussed.

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Recent developments dealing with the age-related alteration of enzymes have been examined. Since the last review of this field, three enzymes have been purified to homogeneity from young and old nematodes (enolase, phosphoglycerate kinase, triosephosphate isomerase) and one from the liver of young and old rats (superoxide dismutase). In all cases except for triosephosphate isomerase, the enzymes from old animals show a reduced catalytic ability compared to those from young animals. In addition, new reports of increases in the amount of altered enzymes in late-passage cells in tissue culture have appeared, though contrary evidence has also been published. The data from these and other papers are compared and discussed. Possible explanations for the alteration of enzymes include error theory, substitution of individual amino acids and conformational change without sequence change. Though final conclusions cannot be made, the evidence favors the latter idea to explain the presence of altered enzymes in old animals.