Paroxysmal nocturnal hemoglobinuria with no evidence of hemolysis presenting as Budd-Chiari syndrome

Paroxysmal nocturnal hemoglobinuria clones in children with acquired aplastic anemia: a multicentre study

A multicentre study evaluating the presence of glycosil phosphatidyl-inositol (GPI)-negative populations was performed in 85 children with acquired aplastic anemia (AA). A GPI-negative population was observed in 41% of patients at diagnosis, 48% during immune-suppressive therapy (IST), and 45% in patients off-therapy. No association was found between the presence of a GPI-negative population at diagnosis and the response to IST. In addition, the response rate to IST did not differ between the patients who were GPI-positive at diagnosis and later developed GPI-negative populations and the 11 patients who remained GPI-positive. Two patients with a GPI-negative population >10%, and laboratory signs of hemolysis without hemoglobinuria were considered affected by paroxysmal nocturnal hemoglobinuria (PNH) secondary to AA; no thrombotic event was reported. Excluding the 2 patients with a GPI-negative population greater than 10%, we did not observe a significant correlation between LDH levels and GPI-negative population size. In this study monitoring for laboratory signs of hemolysis was sufficient to diagnose PNH in AA patients. The presence of minor GPI-negative populations at diagnosis in our series did not influence the therapeutic response. As occasionally the appearance of a GPI-negative population was observed at cyclosporine (CSA) tapering or AA relapse, a possible role of GPI-negative population monitoring during IST modulation may need further investigation.

Large Clones With PNH-Type Phenotype are Not Common in Patients Presenting With Intra-Abdominal Thrombosis—A Prospective Study

Intra-abdominal thrombosis is a complication of paroxysmal nocturnal hemoglobinuria (PNH). There is scarcity of data on cases presenting with thrombosis in whom PNH is the predisposing factor. We assessed the role of PNH defect in 81 patients with intra-abdominal thrombosis, 44 patients of Budd Chiari syndrome and 37 patients of extra hepatic venous obstruction. Flowcytometry with glycosylphosphatidyl inositol-anchored proteins (GPI-AP)-CD55, -CD59, and -CD16 was performed on all patients and controls to assess the prevalence of deficiencies and PNH-type phenotype clone size. Deficiencies of individual GPI-AP were seen in 17.3% cases versus 3.4% controls. This was due to CD55 deficiency on red blood cells and CD16 deficiency on the granulocytes. Deficiency of multiple GPI-APs was less frequent (3.7% cases). Data of this study indicate that the PNH defect as detected with CD55, CD59, and CD16 is not an important cause of intra-abdominal thrombosis in northwestern India.

Mechanisms and clinical implications of thrombosis in paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare acquired disease characterized by a clone of blood cells lacking glycosyl phosphatidylinositol (GPI)-anchored proteins at the cell membrane. Deficiency of the GPI-anchored complement inhibitors CD55 and CD59 on erythrocytes leads to intravascular hemolysis upon complement activation. Apart from hemolysis, another prominent feature is a highly increased risk of thrombosis. Thrombosis in PNH results in high morbidity and mortality. Often, thrombosis occurs at unusual locations, with the Budd–Chiari syndrome being the most frequent manifestation. Primary prophylaxis with vitamin K antagonists reduces the risk but does not completely prevent thrombosis. Eculizumab, a mAb against complement factor C5, effectively reduces intravascular hemolysis and also thrombotic risk. Therefore, eculizumab treatment has dramatically improved the prognosis of PNH. The mechanism of thrombosis in PNH is still unknown, but the highly beneficial effect of eculizumab on thrombotic risk suggests a major role for complement activation. Additionally, a deficiency of GPI-anchored proteins involved in hemostasis may be implicated.

Microvascular thrombosis in the hepatic vein of a patient with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated hemolysis, venous thrombosis, and bone marrow failure. In May 2003, a 33-year-old man was admitted to a hospital with right hypochondralgia and fever. He had a history of aplastic anemia. The patient's diagnosis of diffuse microvessel thrombosis in the hepatic vein due to an unknown cause was derived from the findings of a contrast-enhanced computed tomography examination of the abdominal region, angiographic evaluation of abdominal vessels, and pathohistologic examination of a liver biopsy sample. The patient was subsequently treated with warfarin. The abdominal pain and fever continued, however, and anemia gradually appeared. In April 2004, the patient was referred to our hospital to examine the cause of the thrombosis. On admission, slight anemia and a low serum haptoglobin level were observed. A flow cytometry evaluation of CD55 and/or CD59, CD59, and CD48 expression in erythrocytes, granulocytes, and monocytes, respectively, showed that the respective proportions of negative populations were 5.6%, 97.1%, and 96.2%. The patient then received a diagnosis of aplastic anemia/PNH syndrome, which had caused the hemolytic anemia and thrombosis, although no hemoglobinuria had been observed during his clinical course. This patient is, to our knowledge, the first reported case of a PNH patient with thrombosis present only in hepatic microvessels and not in hepatic large vessels, in spite of the presence of few hemolytic events.