Interestingly, our cDNA-based array analysis in PAXgene-separated RNA samples followed by enzyme activity assay in PBMCs demonstrated that several genes and proteins of the PPP such as glucose-6-phosphate dehydrogenase (G6PDH), transaldolase (TALDO), and transketolase (TK) were upregulated and activated during ME/CFS pathogenesis [21]. Here, TKT is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.