Paroxysmal nocturnal haemoglobinuria with chromosome abnormalities: possible preleukaemia

Cytogenetic and morphological abnormalities in paroxysmal nocturnal haemoglobinuria

Paroxysmal nocturnal haemoglobinuria (PNH) is characterized by the expansion of a haematopoietic stem cell clone with a PIG-A mutation (the PNH clone) in an environment in which normal stem cells are lost or failing: it has been hypothesized that this abnormal marrow environment provides a relative advantage to the PNH clone. In patients with PNH, generally, the karyotype of bone marrow cells has been reported to be normal, unlike in myelodysplastic syndrome (MDS), another clonal condition in which cytogenetic abnormalities are regarded as diagnostic. In a retrospective review of 46 patients with a PNH clone, we found a karyotypic abnormality in 11 (24%). Upon follow-up, the proportion of cells with abnormal karyotype decreased significantly in seven of these 11 patients. Abnormal morphological bone marrow features reminiscent of MDS were common in PNH, regardless of the karyotype. However, none of our patients developed excess blasts or leukaemia. We conclude that in patients with PNH cytogenetically abnormal clones are not necessarily malignant and may not be predictive of evolution to leukaemia.

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.

Chromosomal subclonal evolution in paroxysmal nocturnal hemoglobinuria evolving into acute megakaryoblastic leukemia

Four cytogenetic studies were performed in the course of a paroxysmal nocturnal hemoglobinuria evolving into acute megakaryoblastic leukemia. The clonal evolution was characterized by a unique structural change (9p) at the time of diagnosis, heralding an accelerated and complex karyotypic alteration including 5q-, 12p-, +21, -5, -7. At the terminal phase, the initial population was replaced within 1 week by a new overgrowing clone with -5, +8, +17. This suggests that the paroxysmal nocturnal hemoglobinuria-associated preleukemia and leukemic states share with acute nonlymphocytic leukemia the same nonrandom chromosomal changes.

Normal bone marrow karyotype in paroxysmal nocturnal hemoglobinuria--a cooperative European study

Sixteen patients with paroxysmal nocturnal hemoglobinuria (PNH) from five European centers have been submitted to chromosome analysis. All of them had a normal bone marrow karyotype. The associations between some chromosomally abnormal cases reported in the literature and "typical" PNH or PNH phenomenon during the course of other hematological disorders are discussed.

Paroxysmal nocturnal hemoglobinuria and acute non-lymphocytic leukemia. A report of three cases exhibiting different cytologic types

Three individuals with paroxysmal nocturnal hemoglobinuria (PNH) developed acute non-lymphocytic leukemia (ANLL) as a terminal event. The cytologic types were different in each case suggesting a transformation that may involve a pleuripotent stem cell. Eight previous cases of PNH terminating in acute leukemia have been reported which have also been ANLL in type. Whether PNH should be considered a myelodysplastic or myeloproliferative disorder remains to be seen. PNH has been considered a clonal disorder with several populations of erythrocytes being present. Cytogenetics in the current cases failed to reveal any karyotypic abnormalities during the time PNH was present. However, an abnormal clone appeared in two cases during the time leukemia supervened. Additional studies of PNH as a postulated clonal disorder may provide interesting knowledge for this uncommon disorder.

Two abnormal clones in the bone marrow cells of a patient with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is considered to be a clonal disorder, although most investigations have failed to show chromosomal abnormalities. The present patient suffered from PNH and exhibited in bone marrow cells two abnormal clones with 47 chromosomes in addition to cells with 46 chromosomes. One clone showed trisomy 9, a finding previously reported in leukemias and myeloproliferative disorders. Thus, PNH seems to be a clonal myeloproliferative disease.