Pseudohypertriglyceridemia as a clue: clinical and genetic spectrum of glycerol kinase deficiency in three pediatric cases.

OBJECTIVES: Glycerol kinase deficiency (GKD) is a rare X-linked metabolic disorder caused by pathogenic variants in the GK gene. It can be present in either isolated or complex forms and often mimics primary hyperlipidemia, leading to diagnostic challenges and unnecessary treatment. This study aims to highlight the phenotypic variability and diagnostic features of GKD through a case series.

CASE PRESENTATION: We describe three pediatric patients diagnosed with GKD. Two siblings with isolated GKD presented with persistent, asymptomatic hypertriglyceridemia, confirmed by glyceroluria and genetic testing revealing a hemizygous c.213_214delAT (p.Cys72Ter) mutation. The third patient, diagnosed with complex GKD, presented in infancy with multisystem involvement, including immunodeficiency, hypotonia, splenic abscesses, and elevated and creatine kinase levels. Genetic analysis revealed a 6.9 Mb contiguous deletion spanning Xp21.2-Xp11.4. In all cases, elevated triglyceride levels were unresponsive to therapy, and serum samples lacked lipemic appearance. Lipid-lowering treatments were discontinued following diagnosis, with no adverse outcomes.

CONCLUSIONS: This case series underscores the clinical and genetic heterogeneity of GKD. Urinary glycerol analysis and the absence of serum lipemia are key diagnostic clues. Early recognition is essential to prevent misdiagnosis and guide appropriate management, particularly in treatment-resistant hypertriglyceridemia.