Comparison of patients with familial chylomicronemia syndrome and multifactorial chylomicronemia syndrome.

Context: Patients with rare familial chylomicronemia syndrome (FCS) and relatively common multifactorial chylomicronemia syndrome (MCS) both express severe hypertriglyceridemia, defined as plasma triglyceride concentration ≥10 mmol/L (≥885 mg/dL). Clinically there can be confusion between the two conditions.

Objective: To compare clinical and biochemical phenotypes in patients with genotypically characterized FCS and MCS.

Methods: We performed targeted sequencing of DNA from 193 patients with severe hypertriglyceridemia, classified them as having either FCS or MCS and compared clinical and biochemical characteristics.

Results: FCS compared to MCS patients were significantly younger (31.4 ± 16.7 vs. 51.0 ± 11.3 years; P =0.003), with earlier age at symptom onset (15.0 ± 15.8 vs. 37.8 ± 8.8 years; P =0.00066), lower body mass index (23.3 ± 3.1 vs. 30.7 ± 5.0 kg/m2; P =0.000016), and higher prevalence of pancreatitis events (81.8% vs. 35.2%; P=0.003). Furthermore, FCS compared to MCS patients had a higher ratio of triglyceride to total cholesterol, i.e. 4.18 ± 0.92 vs 1.08 ± 0.51 (P <0.0001) and lower plasma apolipoprotein B, i.e. 0.56 ± 0.15 vs 1.02 ± 0.43 g/L (P <0.0001). MCS patients with heterozygous pathogenic variants had a relatively more severe clinical presentation than other MCS genetic subgroups.

Conclusions: FCS patients have notable phenotypic differences from MCS patients, although there is overlap. While genetic analysis of patients with persistent severe hypertriglyceridemia can definitively diagnose FCS, 8.2% of MCS patients with sustained refractory hypertriglyceridemia behave functionally as if they have FCS, which should influence their eligibility for novel therapies for severe hypertriglyceridemia.