[Type III hyperlipoproteinemia in monoclonal IgM gammopathy]

A 42-year-old woman, found to have increased blood-lipid levels, developed hand-line xanthomas 3 months later. She also had an increased erythrocyte-sedimentation rate and a type lambda monoclonal IgM abnormality. In the course of the following 4 years the IgM concentration rose (from 5.8 to 12.3 g/l) steadily and synchronously with those of the triglycerides (from 147 to 391 mg/dl) and cholesterol (from 212 to 380 mg/dl). During the entire period of observation the ratio of VLDL cholesterol and triglyceride concentrations was elevated (greater than 0.4; normal: less than 0.3). Division of the lipoprotein fractions pointed to a type III hyperlipoproteinaemia. She also had an abnormality of lipid metabolism on the basis of a genetic defect (apolipoprotein-E2 homozygotism), which only manifested itself when an additional factor, IgM paraproteinaemia, was present. Paraproteins thus apparently interfered with the breakdown of the lipoproteins. Neither bezafibrate in increasing doses (200-800 mg daily) with low-fat diet nor administration of lovastatin (20 mg twice daily) together with nicotinic acid (500 mg twice daily) were adequate treatment for this form of auto-immune hyperlipidaemia.