<scp>GPIHBP1</scp> Autoantibody‐Related Hypertriglyceridemia in Children: A Report of Two Cases and a Review of Pediatric Cases From the Literature

BACKGROUND: Severe hypertriglyceridemia (HTG) is rare in children and is often caused by monogenic disorders. However, autoimmune mechanisms, particularly antibodies against glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), have emerged as rare causes. Pediatric-onset GPIHBP1 autoantibody-related HTG remains poorly characterized. METHODS: We evaluated two 3-year-old children with extreme HTG (triglyceride level > 3000 mg/dL). Whole-exome sequencing was performed to investigate monogenic etiologies. Autoimmune testing included antinuclear antibodies (ANAs) and anti-Sjögren's syndrome-related antigen A (SSA) antibodies, as well as an enzyme-linked immunosorbent assay (ELISA) for anti-GPIHBP1 antibodies. A clinical response to immunosuppressive therapy was assessed. A literature review of previously reported pediatric cases was conducted. RESULTS: No pathogenic variants were identified by whole-exome sequencing. Both patients were positive for ANAs (1:320, speckled), and one had high-titer anti-SSA antibodies. The ELISA confirmed the presence of anti-GPIHBP1 antibodies in both cases. Immunosuppressive therapy with hydroxychloroquine effectively reduced the triglyceride level in one patient, while the other required additional prednisolone. At follow-ups (ages 9 and 10), neither patient developed overt systemic autoimmune disease. A literature review revealed 13 previously reported pediatric cases, most of which were diagnosed after the age of 11 years and were frequently associated with systemic lupus erythematosus or other autoimmune disorders. CONCLUSION: GPIHBP1 autoantibody-related HTG is important and potentially treatable severe pediatric HTG, representing an early manifestation of autoimmune dysregulation that requires an accurate diagnosis and longitudinal surveillance.