Homozygous familial hypercholesterolaemia (FH) is a rare genetic disorder with aberrantly high level of low-density lipoprotein cholesterol (LDL-C) requiring multiple combined aggressive lipidlowering therapy to reduce the progression of atherosclerotic cardiovascular disease. Alirocumab, a proprotein convertase subtilisin/kexin type 9 inhibitor (PCSK9i) has been approved for treatment of FH, which requires further lowering of LDL-C in addition to diet modification and maximally tolerated statin therapy. We report the response of short-term alirocumab treatment on a young patient with clinically and genetically confirmed FH, who suffered from acute coronary syndrome, and in particular, discussed the hypothesised legacy effect of PCSK9i. The patient was initially treated with a combination of high-intensity statin and ezetimibe for 12 weeks. Subsequently, alirocumab was added to the patient's lipid-lowering regime and he managed to attain guideline recommended LDL-C target within 10 weeks. However, alirocumab was stopped at week 54 due to financial constraint. Interestingly, despite cessation of PCSK9i therapy for a period of 30 weeks, the patient's LDL-C level rose slightly not returning to his baseline level.