Hemolysis in primary lipoprotein lipase deficiency.

A slight to moderate hemolysis is often present in plasma from patients with primary lipoprotein lipase (LPL) deficiency. To determine the nature of this hemolysis, we measured erythrocyte hypo-osmotic fragility, plasma free hemoglobin, and phospholipid composition in 26 patients with primary LPL deficiency and 21 unrelated controls. In some patients, these investigations were completed by erythrocyte cytoskeletal protein determinations and abdominal echography. Osmotic fragility was similar between control subjects and patients. However, there was a significantly increased concentration of plasma free hemoglobin in primary LPL deficiency (0.282 +/- 0.331 v 0.048 +/- 0.038 g/L in controls, P < .005). In LPL-deficient patients, an increase of plasma lysophosphatidylcholine concentration (12.6% +/- 5.8% v 6.4% +/- 1.9% in controls, P < .0001) was also found. The protein composition of the erythrocyte membrane skeleton was abnormal in some LPL-deficient patients and splenomegaly was present in 12, but these abnormalities did not correlate with plasma free hemoglobin levels. Bilirubin and haptoglobin levels were also within physiologic ranges in these patients, suggesting that the observed hemolysis did not result from hypersplenism. It appears likely that the accumulation of lysophosphatidylcholine was due to an impairment in the reverse metabolic pathway converting lysophosphatidylcholine back to phosphatidylcholine. Collectively, these data, along with a positive correlation between plasma free hemoglobin and lysophosphatidylcholine levels (r = .58, P = .0001), suggest that the hemolysis observed in primary LPL deficiency is mediated to some extent by the abnormally elevated concentration of lysophosphatidylcholine.