Apolipoprotein E deficiency with a depressed mRNA of normal size

We studied a 39-year-old man who had palmar xanthomas complicated with marked hyperlipidemia. His serum cholesterol and triglyceride were 2000 and 6300 mg/dl, respectively. Serum apolipoprotein E (apo E) was undetectable in the patient by the methods of single radial immunodiffusion, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and radioimmunoassay. Serum apo E concentrations of his father and sister were low. This evidence is consistent with a diagnosis of familial apo E deficiency. We studied the synthesis of apo E in cultures of peripheral blood monocyte macrophages (M-M cultures) obtained from the patient, and detected no secretion of apo E in the culture medium and no newly synthesized apo E in the cell lysate. There were only trace amounts of apo E mRNA of the M-M cultures and the size of the mRNA appeared the same as normal apo E mRNA, indicating a different mutation of the gene from that of the case reported by Zannis et al. (J. Biol. Chem., 260 (1985) 12891).