The influence of age and relative weight on the presentation of familial combined hyperlipidemia in childhood

Background: Familial combined hyperlipidemia (FCHL) has been described as the leading cause of familial hyperlipidemia. FCHL is dominantly inherited, occurs in at least 1% of the population, and is responsible for about 10% of premature coronary artery disease (CAD). Objective: Because FCHL in childhood is not well characterized, we evaluated the interrelationships among age, percentage of ideal body weight (%IBW) and plasma lipoprotein levels in FCHL children (age 2-18 years), exploring the possibility that obesity and age may influence the presentation of FCHL in childhood. Methods: One hundred and eighty-nine children with FCHL were studied. Significant correlations within this group were further evaluated by examining a subset of 36 FCHL children, each of whom had an unaffected sibling who could serve as a control for comparison. Results: When the full group was divided into those with TG levels > 90% and those with TG levels < 90%, the correlation with %IBW was stronger in the former (r = 0.45, P < 0.005) as compared with the latter (r = 0.25, P = 0.05). Within the subset of 36 FCHL children and their 36 unaffected siblings (controls), age and sex distributions were similar. Percentage IBW(mean +/- S.D.)(117.3 +/- 29.1 for FCHL and 111.2 +/- 19,4 for controls) was similar and in the overweight range. FCHL children had significantly higher levels of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), apolipoprotein B (ape B) and triglyceride (TG) levels compared with controls (P < 0.0005 for all comparisons). Of several significant correlations observed in the full group (n = 189), only the correlations of %IBW with plasma TG levels (r = 0.45, P = 0.006), and of age with plasma TG levels (r = 0.48, P = 0.003) persisted with a similar degree of magnitude in the subset of 36 FCHL children. No correlation was significant in the controls. By Fisher's Z-test, the correlation between %IBW and TG in the FCHL children was significantly different from controls. Conclusions: These results suggest that TG levels in FCHL children, but not in their unaffected siblings, are sensitive to the presence of obesity, implying an interaction between obesity and the underlying condition. in addition, the association between age and TG level in FCHL children suggests a gradual expression of the hyperlipidemia (i.e. TG) during childhood.