From Persistent Hypertriglyceridemia to Isolated Glycerol Kinase Deficiency: A Case Report

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Abstract
Pseudohypertriglyceridemia (pseudo-HTG) is a rare laboratory phenomenon in which serum triglyceride levels are falsely elevated due to analytical interference from endogenous glycerol, most often caused by glycerol kinase deficiency (GKD), an X-linked disorder caused by pathogenic variants in the GK gene. We report a 50-year-old man referred for persistent hypertriglyceridemia (4.98–7.42 mmol/L) over two years despite dietary modification and statin–fibrate therapy. He had no history of pancreatitis, alcohol intake, diabetes, renal or thyroid dysfunction. Physical examination showed no xanthomas or corneal arcus; body mass index was 26.9 kg/m2. Serum samples were repeatedly visually clear, and lipoprotein electrophoresis revealed an unexpectedly normal lipid distribution. Given the discordance between triglyceride concentrations and the clinical and electrophoretic findings, pseudo-HTG due to GKD was suspected. Glycerol-specific biochemical testing was locally unavailable. Thus, we performed whole genome sequencing (WGS), which identified a likely pathogenic GK nonsense variant, c.1324C>T (p.Gln442Ter), consistent with isolated GKD. Peripheral atherosclerosis and hepatic steatosis were also noted, indicating coexisting cardiometabolic disease. This case highlights isolated GKD as an underrecognized cause of prominent treatment-refractory HTG. In patients with discordant triglyceride results, clear fasting serum, and normal lipoprotein electrophoresis, pseudo-HTG should be considered; genetic evaluation may be informative when glycerol-specific assays are unavailable.

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