Prevalence of familial hyper- and hypolipoproteinemias in blacks: The Princeton School District Family Study

Abstract Using black subjects from the Princeton School Family Study cohort, our specific aim was to estimate the prevalence of suspected familial hyper- and hypolipoproteinemias, and to provide empirical risk estimates for the proportion of probands' first-degree relatives who were similarly affected. Suspected familial hyper- and hypolipoproteinemias were arbitrarily identified in those kindreds having at least two first-degree relatives in the same decile as the proband, top or bottom, respectively, for low- or high-density lipoprotein cholesterol (LDLC, HDLC). Some cutpoint for identification of elevated LDLC must be arbitrarily selected, and the level chosen here, the top decile, will affect ascertainment of the familial disorder. One hundred and seven probands, 52 randomly recalled, 55 from a hyperlipidemic recall group, and their relatives were assessed. Of the 52 randomly recalled black probands, 2 of whom had top decile LDLC, 1 had suspected familial hyperchlosterolemia (FHA). Of the 55 hyperlipidemic recall probands, 25 of whom had top decile LDLC, 4 had apparent FH: one kindred had three-generation vertical and horizontal transmission of top decile LDLC. In the five kindreds with suspected FH, overt disease, drugs, and dietary excess did not appear to cause the elevated LDLC. After adjustment for Quetelet index, there was a significant positive partial correlation between LDLC and both systolic and diastolic blood pressure in top decile LDLC probands and their first-degree relatives. Of the 52 randomly recalled probands, 8 had top decile HDLC, and 2 had suspected familial hyperalphalipoproteinemia (FHA). Of the 55 hyperlipidemic recall group probands, 10 had top decile HDLC, 1 had suspected FHA. In the three kindreds with suspected FHA, the elevated HDLC could not be accounted for by disease, drugs, or alcohol intake known to elevate HDLC. Whatever definition of FH or FHA is used, the high prevalence of suspected FH and FHA underlines the importance of sampling all first-degree relatives of top decile LDLC and HDLC probands; clustering of CHD (or its absence) in families may be related in part to familial aggregation of LDLC and/or HDLC.