Fresh frozen plasma as functional replacement therapy in early infantile ApoC-II deficiency: a molecularly confirmed case series

Objectives Familial chylomicronemia syndrome (FCS) caused by apolipoprotein C-II (ApoC-II) deficiency is a rare and potentially life-threatening disorder characterized by severe hypertriglyceridemia beginning in early infancy. This study aimed to describe the clinical, biochemical, and molecular characteristics of infants with ApoC-II deficiency and to evaluate the therapeutic and diagnostic role of fresh frozen plasma (FFP). Case presentation We report three male infants from consanguineous families presenting with extreme hypertriglyceridemia (range: 3,228–5,802 mg/dL). All patients carried the homozygous APOC2 c.55+1G>C pathogenic variant. A fat-restricted diet was initiated at diagnosis; however, the rate of triglyceride reduction was insufficient for rapid metabolic stabilization. Administration of FFP (10 mL/kg twice daily for three days) resulted in marked biochemical improvement, with up to 98.3 % reduction in triglyceride levels within 72 h. Clinical manifestations included lactescent serum, vomiting, and eruptive xanthomas, which resolved following treatment. Conclusions FFP infusion provides temporary functional ApoC-II replacement, enabling rapid metabolic stabilization while supporting the diagnosis of ApoC-II deficiency in early infancy. Early recognition and timely intervention may help prevent serious complications during the establishment of definitive long-term dietary management.