Pseudo-hypertriglyceridemia in a 2-year-old male with global developmental delay, myopathy and adrenal hypoplasia

Pseudo-hypertriglyceridemia is an overestimation of serum triglyceride levels due to laboratory assays that measure free glycerol concentrations instead of triglycerides directly. Consequently, conditions presenting with elevated levels of endogenous or exogenous free glycerol, such as glycerol kinase deficiency, result in an overestimation of serum triglycerides. Glycerol kinase deficiency (GKD) is caused by pathogenic variants of the GK gene on chromosome Xp21. GKD is characterized biochemically by hyperglycerolaemia and glyceroluria. We herein report a 2-year-old male presented with a history of global developmental delay, axial hypotonia, poor head control and inability to sit unassisted or walk with elevated triglycerides at 683 (normal 44-157 mg/dL). Organic acid analysis showed abnormal accumulation of glycerol. Chromosomal microarray results showed a 4.2 Mb deletion of Xp21.3p21.1 (29296579-33551038) including complete copies of GK, DMD, and NR0B1 genes as well as multiple exons of IL1RAPL1. This confirmed his glycerol kinase deficiency (GKD) as part of the Xp21 continuous gene deletion syndrome. Elevated triglycerides were then recognized as pseudo-hypertriglyceridemia after the diagnosis. The younger sister and the mother have presented with developmental delay, and have been found to have same mutation. This family highlights the importance recognizing pseudohypertriglyceridemia and diagnostic challenges. Earlier identification through urine organic acid analysis could have been made. The combination of clinical presentations and increased glycerol should cause suspicion for GKD.