Unusual dyslipoproteinemia in a patient with primary systemic amyloidosis and nephrotic syndrome. Role of excessive cholesterol synthesis.

We describe a patient with primary systemic amyloidosis, nephrotic syndrome and unusual dyslipoproteinemia. Levels of plasma cholesterol greater than 2,000 mg/dl and triglycerides greater than 3,000 mg/dl were observed. As much as 70% of the plasma cholesterol separated into abnormal very-low-density lipoprotein (VLDL) with cholesterol ester/triglyceride weight ratio of 0.7-1.0. Intermediate-density lipoprotein (IDL) and low-density lipoprotein (LDL) were also elevated, and high-density lipoprotein (HDL) was low. Both LDL and HDL were triglyceride rich. Neither IDL nor LDL was detected after in vitro lipolysis of VLDL triglycerides (95%); hence, IDL and LDL were most probably secreted directly from liver cells. Treatment by weekly plasma exchange was instituted, and the progression of the amyloidosis was slowed. Endogenous cholesterol synthesis, estimated from increments of plasma cholesterol after exchange, was greater than 2,000 mg/dl. We conclude that the unusual dyslipoproteinemia observed in this patient represents a special type of nephrotic syndrome with remarkably enhanced endogenous cholesterol production.