Leukemia and/or Myeloproliferative Syndrome in Neonates With Down Syndrome Alvin Zipursky, Elizabeth Brown, Hilary Christensen, Robert Sutherland, and John Doyle

Approximately 10% of newborn infants with Down Syndrome develop a form of megakaryoblastic leukemia which usually disappears spontaneously during the first months o f life. The evidence that this "Transient Leukemia" is truly leukemia includes the following: it is clonal proliferation, it can be fatal and tissue infiltration o f leukemic cells occurs. Also in approximately 25% of cases that recover, Acute Megakaryoblastic Leukemia will develop in the first four years of life, which, if not treated, is fatal. Evidence regarding the megakaryoblastic nature o f the leukemic cells is presented as well as a description o f the lethal forms of the disease. The study o f Transient Leukemia is o f considerable importance because it can provide insight into both the nature o f leukemia and its relation to trisomy 21. Copyright �9 1997 by W.B. Saunders Company

L eukemia is more f requent in Down syn- drome than in normal children. ~ Also, new-

born infants with Down syndrome have a ten- dency to develop a disorder which resembles acute megakaryoblastic leukemia, except that it disappears spontaneously during the first months of life. Because of the spontaneous dis- appearance of the disease, it has been difficult to accept it as leukemia, and therefore it has been referred to by various nonleukemic names such as transient myeloproliferative disorder, transient blastemia, and transient abnormal my- elopoiesis. In this article, we shall provide evi- dence that this disorder is truly leukemia, that it often is not transient and indeed may be fatal, that it is closely related to the increased fre- quency of leukemia (which is seen in children with Down syndrome), and that it represents a unique proliferation of a hematopoiet ic precur- sor cell. For these reasons we refer to the disease as transient leukemia (TL).

Classically, the disease is found in a clinically normal child with Down syndrome who acciden- tally is found to have an elevated white blood count with primitive blasts in the peripheral blood. An example of such a case is shown in Fig 1, and this shows several interesting features of this disease. To begin with, the blast count is very high and it persists for a period of several months, but then the blasts disappear com- pletely. A second interesting feature is a "recur- rence" of the disease with an increase in the number of blasts, which is observed not uncom- monly. As is characteristic of transient leukemia,

the blasts disappeared from the blood in the first 3 months of life, and thereafter the child was clinically and hematologically well. The number of blasts seen in these cases varies from relatively few to extremely high numbers as shown in Fig 2.

TL occurs only in newborn infants with Down syndrome, or in newborns who are phenotypi- cally normal but are trisomic for chromosome 21.2 In a prospective study of blood films of chil- dren born with Down syndrome, we found that 8 of 77 or 10.4% had blasts in their peripheral blood consistent with the diagnosis of TL. It would appear therefore that TL appears rela- tively frequently in newborn infants with Down syndrome.

Thrombocytopenia was found in several o ther cases in our series of 37 TL patients (Fig 3). It is evident that the majority of cases have normal platelet counts, but thrombocytopenia was found in some and thrombocythemia in others. Thrombocythemia has been repor ted pre- viously. 3 Anemia, al though uncommon, does oc- cur so that there is evidence that erythropoiesis is also affected in this group. On the o ther hand, there is no evidence that myelopoiesis is affected

From the Division of Hematology/Oncology, Department of Pediat- rics, Hospital for Sick Children and the Department of Medicine, University of Toronto, Toronto, Ontario, Canada. Address reprint requests to Alvin Zipursky, MD, Department of Pedi- atrics, Division of Hematolog3 / Oncology, Hospital for Sick Children, 555 University Ave, Toronto, Ontario, Canada M5G IX8. Copyright �9 1997 by W.B. Saunders Company 0146-0005/97/2101-0013505.00/0

Seminars in Perinatology, Vol 21, No 1 (February), 1997: pp 97-101 97

9 8 Zipursky et al

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Figure 2. Peripheral blood blast counts in a series of Figure 3. Platelet counts in a series of cases of TL. cases of TL. The shaded area represents the normal range.

Neonatal Leukemia in Down Syndrome 99

Figure 4. Bone marrow biopsy from a child with TL and thrombocytopenia. The large cells are megakary- ocytes, many of which are dysplastic.

sophils were present in the peripheral blood, but there were increased numbers of blasts. How- ever, the cells of the pericardial effusion were predominately basophils.

Therefore, it would appear that TL is associ- ated with the appearance in the blood of a primi- tive hematopoiet ic cell, which seems to affect platelet, red blood cell, and basophil numbers.

Bone marrow aspirations were performed in 16 patients in our series. The number of blasts in the marrow varied from 3% to 50% even in the presence of very large numbers of blasts in the peripheral blood. There was a direct rela- tionship between the percentage of blasts in the marrow and the numbers in the peripheral blood (P < .05); in some cases there was a lower percentage of blasts in the marrow than in the peripheral blood, a p h e n o m e n o n that is not ob- served in o ther forms of leukemia but is common in TL. Frequently, micromegakaryocytes and dys- plastic megakaryocytes were observed in the mar- row, but what was most striking was the appear- ance of marrow biopsies. Figure 4 shows a marrow biopsy in a child with TL and thrombo- cytopenia; the marrow contains an increased numbers of megakaryocytes, most of which are dysplastic. This picture of thrombocytopenia in the peripheral blood with a bone marrow con- taining increased numbers of megakaryocytes, many of which are dysplastic, is found also in the syndrome of myelodysplasia, which occurs in older children with Down syndrome, 6 as will be noted.

It is evident from the previously ment ioned observations that TL is a disorder characterized by increased numbers of blasts in the peripheral

blood, variable anemia and thrombocytopenia, and bone marrow aspirates that contain only a partial infiltration of blasts and evidence of ab- normal megakaryocytopoeisis.

On light microscopy, the leukemic cell of TL appears as an undifferentiated blast. Cytoplasmic blebbing is consistent with the appearance of megakaryoblasts; however, the morphology by light microscopy cannot be considered diagnos- tic. However, what is more striking is the electron microscopic features of these cells. Many of these cells are relatively undifferentiated blasts which express megakaryocyte antigens as evidenced by immunogold labeling. 7 In some cells, however, there is considerable ultrastructural evidence of megakaryocyte differentiation with ectoplasmic blebbing, alpha granules, and demarcat ion membranes (Fig 5). This ultrastructural evi- dence is supported by flow cytometry, which shows evidence of early (CD61 and CD42), but not late megakaryocyte antigens (CD62).

The previous observations suggest that TL is a form of megakaryoblastic leukemia. Having said that, the authors would like to ment ion briefly their observations concerning culture of these cells, which indicate that al though these cells

Figure 5. An electron micrograph of a leukemic cell from the peripheral blood of a patient with TL. The cell contains demarcation membranes (arrows) of ab- normal structure and alpha granules (arrow heads). Immunogold labeling was positive for surface CD61 antigen.

1 0 0 Zipursky et al

have megakaryoblastic features, they have the potent ial for forming other cells. We B and oth- ers 8 have repor ted studies of in vitro cultures, which indicate that these cells have the potential for fo rming cells not only of megakaryocyte lin- eage, but also of erythroid and basophil lineages.

In the following sections, evidence will be pre- sented that TL, a disorder that can disappear spontaneously, is indeed leukemia, and that in some cases it is not transient but is lethal.

We have repor ted a series of cases of TL in Down syndrome in which the clinical course is very severe. 9 The disease is characterized by hy- drops fetalis resulting in intrauterine death, still- birth, or a severe neonatal disease that may be fatal or f rom which the child may recover com- pletely. O f 13 cases studied by us or repor ted in the literature, 9 five were stillbirths and eight were born alive. O f these, five survived and three died in the neonatal period. Hydrops was no ted in nine cases. Pericardial effusions were no ted in six cases, three of whom did not have hydrops. At autopsy, infiltration with leukemic cells were no ted in the tissues of liver, spleen, pancreas, and in soft tissues. Thus TL can be a fatal disease, characterized by a massive accumulat ion of prim- itive blasts in the per ipheral b lood and with leu- kemic cell infiltrates. All these features are con- sistent with a leukemic process.

There is fur ther evidence to support the con- cept that TL is leukemia. Although most studies have shown that in TL, the cytogenetics of the cells are normal, we 1~ and others 11 have observed clonal cytogenetic abnormalities in TL. In our series of 37 cases, only one had a clonal abnormal- ity, which disappeared as the blasts disappeared. Thus, al though it is uncommon, the presence of karyotypic abnormalities in some cases (ie, evi- dence of a clonal proliferation) supports the con- cept that TL is leukemia. This is further sup- por ted by two studies 12'13 indicating, with molecular biological techniques, that the prolifer- ation in TL is clonal. Therefore, we conclude f rom all this evidence that TL is truly leukemia, and that in many cases it is not transient but fatal.

To comple te the clinical picture of TL, one o ther disorder should be ment ioned, namely a severe form of hepatic disease that manifests in the first few weeks of life and may be progressive, with a majority of cases dying within the first few months of life. 14'15 Death occurs f rom progres- sive liver failure, and at autopsy the findings are severe hepatic fibrosis.

One final impor tan t piece of evidence linking TL to leukemia is that patients who have recov- ered f rom TL have frequently developed acute megakaryoblastic leukemia (AMKL) in the first 4 years of life. We have recently studied a series of 23 children with DS or mosaic DS observed at the Hospital for Sick Children f rom July 1986 through August 1994.16 Of 19 surviving children, four developed myelodysplasia (MDS; the early phase of AMKL) between 70 and 119 months of age. In suppor t of these results was a question- naire survey pe r fo rmed in the Uni ted States. Of 85 cases of TL, it was found that 33% had devel- oped leukemia in the first 3 years of life. 17 It would therefore appear that the incidence of MDS/AMKL deve lopment in patients recovered f rom TL is approximately 25% to 30%. In pa- tients who had no evidence of TL, the incidence is less than 1%. Therefore , TL is a pre-leukemic disorder.

All these observations provide a basis for a theory concerning the development of the mega- karyoblastic leukemias in Down syndrome. These " leukemias" refer to (1) TL, (2) myelo- dysplasia (a syndrome characterized by thrombo- cytopenia in a child who is clinically well and whose bone marrow contains megakaryoblasts and increased numbers of megakaryocytes, most of which are dysplastic); and (3) AMKL. It should be added that 100% of cases of MDS will develop AMKL. Indeed, the line separating these two entities is arbitrary, with MDS having less than 30% blasts in the marrow and AMKL more.

We postulate that a hematopoie t ic precursor cell proliferates abnormally in Down syndrome fetuses, and this proliferation usually disappears in the first few weeks or months after birth. We think this may indicate that there is a maternal factor involved in this proliferation. This prolif- eration occurs only in cells that are trisomic for ch romosome 21, as evidenced by children with mosaic trisomy 211s; in them, the proliferation is restricted to cells with trisomy 21. In most cases, the accumulat ion of blasts disappears spontaneously and the child is well; however, in some cases the disease is fatal because of the development of hear t failure and hydrops or he- patic fibrosis.

The frequency with which this process occurs is of considerable interest. Using the observa- tions described previously, it is likely that about 10% of newborn infants with Down syndrome have TL. Because 25% of these cases will develop

Neonatal Leukemia in Down Syndrome 10 1

MDS/AMKL a n d because MDS/AMKL occurs in abou t 0.5% of all ch i ld ren with Down syndrome, it would appea r that all or mos t cases of M D S / AMKL occur in ch i ld ren who have recovered f rom TL.

The above theory mus t be proven; however, one observat ion that speaks against the theory that all MDS/AMKL cases arise in ch i ld ren who

had TL at b i r th is the fol lowing observat ion. The re has b e e n a r epor t 19 of twin girls with Down

syndrome, one of w h o m had TL at bir th; no evidence of TL was f o u n d in the other . Two years later, the chi ld who did no t have TL deve loped MDS/AMKL, whereas the o the r chi ld has re- m a i n e d well a n d free of leukemia . It is o f course possible that the o n e chi ld with no evidence of l eukemia at b i r th had TL that a p p e a r e d a n d dis- appea red d u r i n g fetal life.

The study of TL is o f cons ide rab le i m p o r t a n c e because it can provide ins ight in to bo th the na- ture of l eukemia a n d its re la t ion to tr isomy 21. The fol lowing are postulates that can a n d will be tested in f o r t h c o m i n g studies:

1. T h e r e is a factor in m a t e r n a l b lood that af- fects the prol i fera t ion, d i f ferent ia t ion , a n d / or the survival of a hematopo ie t i c p recursor cell bea r ing tr isomy 21.

2. Most if n o t all cases of MDS/AMKL in Down

syndrome arise in ch i ld ren who have had TL at birth. A proper ly con t ro l l ed prospective study can conf i rm or reject this hypothesis.

3. TL proceeds to MDS a n d thence to AMKL as a result of a genet ic change in one or more cells in the p o p u l a t i o n of blasts in TL. Subse- quent ly , this p o p u l a t i o n expands to b e c o m e MDS a n d thereaf te r AMKL.

References

1. Robison LL, Nesbit ME Jr., Sather HN, et al: Down syn- drome and acute leukemia in children: A 10-year retro- spective survey from Children's Cancer Study Group. J Pediatr 103:235-242, 1984

2. Jones GR, Weaver M, Lang WE: Transient blastemia in phenotypically normal newborns. AmJ Pediatr Hematol Oncol 9:153-157, 1987

3. Miller JMcC, Sherrill MD, Hathaway WE: Thrombocy- themia in the myeloproliferative disorder of Down's Syn- drome. Pediatrics 40:84%850, 1967

4. Lazarus KH, Heerema NA, Palmer CG, Baehner RL: The myeloproliferative reaction in a child with Down syn- drome: Cytological and chromosomal evidence for a transient leukemia. Am J Hematol 11:417-423, 1981

5. Zipursky A, Doyle J, Christensen H, et al: Leukemic cells in the Transient leukemia of Down Syndrome. Blood 80:32a, 1992 (abstr)

6. Zipursky A, Thorner P, De Harven E, et al: Myelodys- plasia and acute megakaryoblastic leukemia in Down Syndrome. Leukemia Res 18:163-171, 1994

7. Zipursky A, Christensen H, de Harven E: Ultra.structural studies of the megakaryoblastic leukemias of Down syn- drome. Leukemia Lymphoma 18:341-347, 1995

8. Suda J, Eguchi M, Akiyama Y, et al: Differentiation of blast cells from a Down's syndrome patient with transient myeloproliferative disorder. Blood 69:508-512, 1987

9. Zipursky A, Rose T, Skidmore M, et al: Hydrops fetalis and the neonatal leukemia of Down Syndrome. J Pediatr Hematol Oncol 13:81-87, 1996

10. Zipursky A, Doyle J: Letter to the Editor: Leukemia in newborn infants with Down Syndrome. Leukemia Res 17:195, 1993

11. Ghosh Fa Transient abnormal myelopoiesis in Down's syndrome: Are some of them truly leukemic? Leukemia Res 16:545-546, 1992

12. Kuruhashi H, HaraJ, Yumura-Yagi K, et al: Monoclonal nature of transient abnormal myelopoiesis in Down's syndrome. Blood 77:1161-1163, 1991

13. Miyashita T, Asada M, Fujimoto J, et al: Clonal analysis of transient myeloproliferative disorder in Down's Syn- drome. Leukemia 5:56-59, 1991

14. MiyauchiJ, Ito Y, Kawano T, et al: Unusual diffuse liver fibrosis accompanying transient myeloproliferative dis- order in Down's Syndrome: A report of four autopsy cases and proposal of a hypothesis. Blood 80:1521-1527, 1992

15. Ruchelli ED, Uri A, DimmickJE, et al: Severe perinatal liver disease and Down Syndrome: An apparent relation- ship. Human Pathol 22:174-180, 1991

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18. Doyle JJ, Thorner P, Poon A, et al: Transient leukemia followed by megakaryoblastic leukemia in a child with mosaic Down Syndrome. Leukemia Lymphoma 17:345- 350, 1995

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