A Small Change Can Make a Big Difference: A Lesson from Evolocumab.

BACKGROUND: Evolocumab is an expensive proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor which has been shown to significantly improve cardiovascular outcomes in high risk patients.

METHODS: This is a case study describing a stepwise approach to "PCSK9 inhibitor non-response" in a patient with familial hypercholesterolaemia. There are a few described pathophysiological mechanisms for "PCSK9 inhibitor non-response" including homozygous LDL-C receptor-negative mutations and alteration in the binding site of PCSK9 inhibitors.

RESULTS: We report the case of a 41-year-old woman with familial hypercholesterolaemia and premature cardiovascular disease, who was non-responsive to the action of PCSK9 inhibitor solely due to the incorrect subcutaneous injection technique.

CONCLUSIONS: This case study highlights the importance of reviewing the accuracy of SC injection technique in patients with minimal or no response to PCSK9 inhibitors prior to proceeding to costly genetic testing.