PAROXYSMAL NOCTURNAL HEMOGLOBINURIA PRESENTING AS APLASTIC ANEMIA IN A CHILD. CASE REPORT WITH EVIDENCE OF DEFICIENT LEUKOCYTE ACETYLCHOLINESTERASE ACTIVITY

Leukemia arising out of paroxysmal nocturnal hemoglobinuria

In paroxysmal nocturnal hemoglobinuria (PNH), one or more hematopoietic stem cells that are defective in GPI anchor assembly as a result of mutation in the PIG-A gene preferentially expand in the bone marrow and give rise to peripheral blood elements that are deficient in GPI anchored protein expression. According to current concepts, 5-15% of PNH patients develop leukocyte dyscrasias which invariably are acute myelogenous leukemia (AML). In this review, the literature from 1962 to the present is analyzed regarding the type of leukocyte dyscrasia, incidence, and cytogenetic features of the abnormal cells that have been reported. Among a total of 119 cases that are well-documented, 104 myeloid dyscrasias involving several categories in addition to AML, as well as 15 lymphoid dyscrasias are described. Of 1,760 patients in 15 series that contain 20 or more patients, 16 (1%) are reported as having developed "acute leukemia." However, of 288 listed as having died, 13 (5%) are recorded as having had "acute leukemia." In 32 of the patients with hematological dyscrasias where karyotypes were analyzed, 7 were found to be normal and 25 found to harbor various alterations with the +8 abnormality present in 8. In 5 of 7 instances evidence indicates that the dyscratic cell arises from the PNH clone. Processes potentially involved in the evolution of the dyscratic cells from PNH clones are discussed.

A platelet and granulocyte membrane defect in paroxysmal nocturnal hemoglobinuria: usefulness for the detection of platelet antibodies

The tendency of platelets and leukocytes to lyse after their interaction with antibody and complement was studied by measuring the release of (51)Cr from cells labeled with this isotope. Platelets from six patients with paroxysmal nocturnal hemoglobinuria (PNH) were 15-230 times more sensitive to antibodies and 10-32 times more sensitive to complement than normal platelets or platelets from patients with other types of thrombocytopenic or hemolytic disorders. Mixed white blood cell (WBC) preparations from patients with PNH were 3-20 times more sensitive to anti-WBC antibodies and 5-10 times more sensitive to C' than were WBC preparations from normal subjects, but PNH lymphocytes showed normal immunologic reactivity. PNH platelets, like PNH erythrocytes, lysed more readily than normal platelets in acidified serum and in media of reduced ionic strength, but these characteristics were not demonstrable with PNH WBC's under the conditions of study. In PNH, platelets appear to comprise a single population with respect to their sensitivity to immune lysis, yet their survival time as measured with (51)Cr falls within normal limits. PNH granulocytes likewise appear to consist of a single, uniformly sensitive population. It is concluded that, in PNH, platelets and granulocytes share the membrane defect characteristic of erythrocytes in this disorder. These observations support the concept that PNH arises as the result of a somatic mutation in a primitive cell capable of differentiating into erythroblast, myeloblast, and megakaryoblast lines. PNH platelets or enzymatically treated normal platelets permit the detection of some types of platelet antibodies in dilutions up to 2000-fold greater than is possible with currently available methods, a finding suggesting that the immune lysis technique will prove useful for the study of platelet immunology.

Disorders of the red cell membrane: a review of biochemical and physiologic alterations of erythrocyte membranes which may lead to morphologic changes and shortened cell survival

Morphologically similar cells can be seen in such varied conditions as liver disease, renal disease, a-betalipoproteinemia, malab sorption states, congenital nonspherocytic anemias, thalassemia, iron deficiency, pykno cytosis, hemolytic-uremic syndrome, erythro cyte enzyme deficiencies, etc.

The common denominator in these condi tions may be an increase in membrane rigid ity, resulting from a diversity of causes. These would include altered protein-lipid- carbohydrate composition, abnormally struc tured hemoglobins, the presence of Heinz bodies due to altered glycolysis or unstable hemoglobins. The end result of such altered membrane elasticity, regardless of cause, would be fragmentation and destruction of the red cells during passage through small vascular channels, particularly in the spleen. Changes in erythrocyte stromal composi tion often seem to reflect more generalized systemic metabolic disorders. Whether any of the alterations of membrane composition are causally related to either the morpho logic changes or the shortened cell survival still remains to be proven.