ABSTRACT
There is another context in which FDB3500 is of theoretical interest. In FH, the LDL receptor is defective and this must interfere to some extent with uptake of apoE-rich lipoproteins such as IDL and chylomicron remnants. In many patients with FH, therefore, in addition to the increased LDL, there is also some increase in IDL (though obviously not to the same extent as in type III hyperlipoproteinaemia, because the remnant receptors for IDL are functioning and because apo E may still bind to mutant receptors better than apo B100). In FDB3500, only lipoproteins dependent on apo B100 for receptor binding are expected to accumulate in the circulation, and thus serum LDL alone should be elevated if current theories about the clearance of apo E-containing lipoproteins are correct. Serum LDL does indeed appear to be the sole lipoprotein that is increased in FDB3500.
