Acute myocardial infarction in an 8-year old male child with homozygous familiar hypercholesterolemia: laboratory findings and response to lipid-lowering drugs.

Background: Homozygous familial hypercholesterolemia (HoFH) is a rare, inherited metabolic disease, caused by low-density lipoprotein (LDL) receptor abnormality, consequently leading to an increase of serum levels of LDL cholesterol (LDL-C). Clinically, this disease is characterized by the deposition of LDL-C in skin, tendons, and arterial wall. Children with HoFH develop significant coronary artery disease (CAD) in the first decade of life and frequently die of myocardial infarction (MI) before 20 years of age.

Methods: An 8-year-old boy with a diagnosis of acute MI on January 15, 2012 was admitted to our hospital for further evaluation of the potential cause and treatment. He had severe hypercholesterolemia for the past several years and showed typical signs of FH. Laboratory work-up excluded secondary causes of hypercholesterolemia and a diagnosis of HoFH was made after assessing the lipid profiles of his parents and his relatives. After careful consideration, he was prescribed a combination regime of lipid-lowering therapy. The plasma pro-protein convertase subtilisin/kexin type 9 (PCSK9) levels were also evaluated for him and his family members.

Results: His total cholesterol (TC) was 18.96 mmol/L and both parents had hypercholesterolemia (TC of mother: 7.46 mmol/L and father: 8.74 mmol/L). The plasma level of PCSK9 of the patient was significantly higher than his parents and his uncles and this pattern was similar with the level of their lipid profile. Importantly but not surprisingly, his serum lipid profile was not significantly improved by concomitant use of rosuvastatin 10 mg and ezetimibe 10 mg daily for one month, even a double dose of rosuvastatin and ezetimibe 10 mg daily for another month.

Conclusions: The present case may have an important clinical implication for future investigation regarding the relation of HoFH to statin and PCSK9.