This Figure illustrates the LDL-C levels in untreated HoFH and HeFH patients.  On average, untreated HoFH patients will have LDL-C levels ≥465 mg/dL.  Treated HoFH patients never attain normal LDL-C levels; typically serum LDL-C levels are > 300 mg/dL, even on maximum therapy.  

This is not true for heterozygous FH patients.  Multiple studies have found that, on average, heterozygous FH patients on maximal lipid lowering therapy will see their LDL-C levels decrease to a mean of 135 mg/dL.  This is not true, however, for patients with severe heterozygous FH.  Even on maximum lipid-lowering therapy, these patients will still have seriously elevated LDL-C levels, >200 mg/dL if they have documented CHD or >300 mg/dL if they have not yet had a CHD event.  These severe heterozygous FH patients will typically have CHD in the fourth and fifth decades of life.