Comprehensive analysis of Chinese patients with non-LPL familial chylomicronemia syndrome: Genetic variants, dietary interventions, and clinical insights.

Background: Familial chylomicronemia syndrome (FCS) comprises a group of ultrarare disorders caused by biallelic variants in LPL or, less frequently, by GPIHBP1, APOC2, APOA5, or LMF1.

Objectives: To evaluate the phenotypes and management of eight non-lipoprotein lipase (LPL)-FCS patients.

Methods: Seven pediatric and one adult patients with non-LPL-FCS were enrolled. Clinical features, treatment outcomes, and genetic profiles were assessed.

Results: Among the 33 patients with FCS, 25 (76%) had LPL-FCS and eight (24%) had non-LPL-FCS; five had variants in GPIHBP1, one each in the LMF1, APOC2, and one with composite heterozygous variants in APOA5 and LPL. Twelve non-LPL variants were identified, five of which were novel variants in GPIHBP1 and two in LMF1. In silico predictions indicated that all novel variants might impact protein function. Elevated baseline triglyceride (TG) levels [22.9 (17.4-30.8) mmol/L, 2026.7 (1540.0-2728.5) mg/dL] were observed in all patients. Among the pediatric patients (7/7), chylomicronemia was the most common onset symptom. Acute pancreatitis was observed in only one patient with LMF1-FCS during pregnancy. The frequency of symptoms and lipid levels in the non-LPL-FCS group were slightly lower than those in the LPL-FCS group (P > 0.05). Dietary fat restriction reduced TG levels by 84.0% to 4.21 mmol/L (372.6 mg/dL, P < 0.01). Compared with other non-LPL-FCS patients, GPIHBP1-FCS patients experienced greater challenges in managing TG levels (P < 0.05).

Conclusion: This study unveiled the genetic profile of the Chinese FCS cohort and enriched the mutation spectrum of non-LPL-FCS. The clinical characteristics and treatment outcomes of patients with non-LPL-FCS were delineated.