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

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.