[Erythrocyte from Duchenne muscular dystrophy is fragile]

Intermittent indirect hyperbilirubinemia was occasionally observed in Duchenne muscular dystrophy (DMD) patients. We suspected that hyperbilirubinemia might be caused by hemolysis of fragile erythrocytes due to damaged endothelium, which was reported in DMD. To examine the fragility of erythrocytes, we performed osmotic resistance test in 25 DMD, 12 myotonic dystrophy (DM), 12 amyotrophic lateral sclerosis (ALS) and 24 healthy volunteers (male 15, female 9). Minimum resistance (beginning point of hemolysis) of DMD (0.447 +/- 0.016%) was higher than that of age matched male controls (0.425 +/- 0.018%: p = 0.0008) and that of DM (0.440 +/- 0.015%) was also higher than that of total controls (0.423 +/- 0.016%, p = 0.0077). The number of poikilocytes was increased in DMD (35.45 +/- 41.17 per a high magnitude field), however no obvious correlation was detected between the ratio of poikilocytes and resistances. Total bilirubin showed correlation (p = 0.029) to minimum resistance. These findings suggested that erythrocyte membrane is fragile in DMD. Involvement of endothelial damage could not be proven, because all investigated patients showed normal tissue plasminogen activator inhibitor-1. Although the mechanism of fragile erythrocytes in DMD is still unknown, we should pay attention to interpret bilirubin in DMD, because hemolysis due to erythrocyte fragility may influence the value.