Association of apolipoprotein(a) phenotypes in children with family history of premature coronary artery disease.

Although blacks have higher plasma levels of lipoprotein(a) [Lp(a)] than whites, the Lp(a) levels are not associated with clinical coronary artery disease (CAD) or parental history of myocardial infarction in blacks. To explore whether ethnic differences in the pathogenicity of Lp(a) are related to the thrombogenic component of Lp(a), this study investigated in children the associations of apolipoprotein(a) [apo(a)] phenotypes and Lp(a) levels with family history of premature CAD. Subjects were 46 children aged 7 to 11 years divided according to family history of premature CAD and assessed for Lp(a), apo(a) phenotypes, and other lipids and lipoproteins. The prevalence of small isoforms was higher in children with positive family history of premature CAD than in children with negative family history of premature CAD (32% versus 10%). Large isoforms were more prevalent in whites (24% versus 6%), and medium-sized isoforms were more prevalent in blacks (75% versus 52%). The black/white difference was smaller (19% versus 24%) in regard to small isoforms. Lp(a) levels were inversely related to apo(a) size in both blacks and whites (P = .084 and P = .049, respectively). Single-banded small apo(a) isoforms predicted positive family history of premature CAD, independent of ethnicity and Lp(a) levels. Small apo(a) isoforms in children were independent predictors of family history of premature CAD. Unlike Lp(a), they appear to be equally pathogenic for blacks and whites.