Management of a patient with a null low-density lipoprotein receptor mutation: a case report.

A 13-year-old Greek boy with severe dyslipidemia, large tuberous xanthomas over the knees and elbows, Achilles' tendon xanthomas, and a bilateral corneal arcus was referred to the Lipid Clinic. He had a supravalvular aortic stenosis, 50% to 60% stenosis of both carotid arteries, and normal coronary arteries. Familial hypercholesterolemia was clinically diagnosed. A V408M null low-density lipoprotein receptor (LDLR) mutation was identified in homozygosity. He responded to lipid-lowering drugs by decreasing total cholesterol by 32%, low-density lipoprotein cholesterol by 33%, and triglyceride levels by 30%. Additional treatment with low-density lipoprotein-apheresis further decreased total cholesterol by 52%, low-density lipoprotein cholesterol by 55%, and triglycerides by 43%. Low-density lipoprotein cholesterol levels between apheresis sessions showed a declining pattern. A significant regression of tuberous xanthomas was noted. A suitable combination of lipid-lowering drugs is effective even in this case of homozygosity for a null LDLR mutation. Furthermore, the coadministration of statins, cholestyramine, and ezetimibe during low-density lipoprotein-apheresis tends to counterbalance the postapheresis relapse in low-density lipoprotein cholesterol levels.