American Journal of Hematology 21:315-322 (1986)

Nuclear Bridging of Erythroblasts in Acquired Dyserythropoiesis: An Early and Transient Preleukemic Marker Nicholas C. Bethlenfalvay, T.A.J. Phaure, Robert L. Phyliky, and Robert P. Bowman

Department of Primary Care, Fitzsimons Army Medical Center, Aurora, Colorado (N. C. B.), Department of Haematology, Staffordshire General Infirmary, Stafford, United Kingdom, (TA. J. P.). The Mayo Clinic, Rochester, Minnesota (R. L. P.), and Department of Medicine, Brooke Army Medical Center, Fort Sam Houston, Texas (R.P.B.)

The clinical, hematologic, and histological characteristics of two patients who pro- gressed from refractory anemia to acute leukemia are described. When first studied, nuclear bridging of erythroblasts, similar to that seen in congenital dyserythropoietic anemia type I and megakaryocytic dysplasia, were the only abnormalities. Within 6 years, both patients died, the first of acute nonlymphocytic leukemia, the second of erythroleukemia. Nuclear bridging of erythroblasts in the marrrow of these patients was an early and transient phenomenon and was not observed during the terminal phase of leukemia.

Key words: preleukemia, dyserythropoiesis, nuclear bridging of erythroblasts

INTRODUCTION

Several comprehensive reviews have recently appeared on the clinical, hemato- logic, and biological features of dysmyelopoiesis and preleukemia [ 1-61, and a proposal for the classification of the myelodysplastic syndromes has been published [7]. The observation of nuclear bridging of erythroblasts in early stages of preleuke- mia has not been mentioned by these authors.

We wish to report two cases of refractory anemia in whom the earliest morpho- logic clues of the preleukemic state were related to the marrow erythroid series revealing internuclear bridging of erythroblasts and to dysmorphysm of the mega- karyocytic lineage. Both patients were dead of a malignant myeloproliferative disease within 6 years after the initial observation. A brief report on the second patient, then thought to be a late recognized case of congenital dyserythropoietic anemia type I (CDA-I), has been published [8].

MATERIALS AND METHODS

Two elderly patients with mild refractory macrocytic anemia were observed for a period of 5 years and the evolution of their disease documented.

Received for publication May 14, 1985; accepted September 5, 1985. Dr. Bowman’s current address is 1705 Hospital Street, Greenville, MS 38701. Address reprint requests to Dr. Bethlenfalvay, Dept. of Primary Care, Fitzsimons Army Medical Center, Aurora, CO 80045.

0 1986 Alan R. Liss, Inc.

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LABORATORY METHODS

Case Report: Bethlenfalvay et al

Routine hematological and chemical investigations were carried out by standard methods. The bone marrow was studied by light microscopy of stained smears and sections of core biopsies. Iron stores were estimated by marrow smears stained with the prussian blue method.

CASE REPORTS Case 1

This 75-year-old man presented at the Staffordshire General Infirmary in April 1975 with macrocytosis found on routine evaluation in connection with his hyperten- sion. Aside from this diagnosis, his general health had been excellent.

Laboratory examinations. Blood counts are summarized in Table I. The peripheral blood film showed slight macrocytosis and a few distorted red cells.

Bone marrow. The marrow showed erythroid hyperplasia with dyserythro- poietic features, namely nuclear bridging, karyorrhexis, and binuclearity of erythro- blasts. Few megakaryocytes were dysmorphic (Fig. lA,B). The myeloid series appeared normal and the iron stain showed normal iron content and distribution.

Clinical course. In view of the suspicion of a preleukemic state, the patient was followed at regular intervals. In 1979, the peripheral blood showed anisocytosis, crenated cells, and increased polychromasia. He was hospitalized in May 1980 with lassitude and shortness of breath. There was no hepatosplenomegaly . Marked aniso poikilocytosis and, for the first time, myeloblasts were seen in the peripheral blood (Table I). A bone marrow aspirate produced sinusoidal blood only. Cells recognized as blasts both in peripheral and sinusoidal blood had pale blue cytoplasm exhibiting no protrusions. The nuclearkytoplasmic ratio was 6:4, and occasional cells contained a single Auer rod. Histochemical staining for myelo or platelet peroxidase in these cells was not done. A trephine biopsy of the right iliac crest revealed features of myelofibrosis with scattered nests of megakaryocytes and blast cells (Fig. 2).

During the remaining 5 months of his life, the patient’s condition was managed conservatively with blood transfusions and antibiotics when indicated. He died in October 1980. A postmortem examination was not performed.

TABLE I. Laboratory Data of Case 1

April 1975 November 1979 May 1980 October 1980

Hemoglobin (g/dl) 11.2 12.2 6.9 8.0 Erythrocytes ( X 10l2/1) 3.26 2.84 3.00 Hematocrit (%) 34.2 22.3 24.3 MCH (pg) 34.4 25.0 27.4 MCHC (g/dl) 32.8 31.6 34.0 MCV (FI) 105 83 77 19 Anisocytosis t ++ +++ ++ Poikilocytosis ++ +++ ++ Leukocytes ( x 109/1) 3.0 9.8 5.2 2.9

21 30 Myeloblasts (%) - - Platelets ( x 109/1) 109 220 1 I6 57

Case Report: Erythroid Nuclear Bridging in Preleukemia 317

Fig. 1. Case 1. Wright-stained marrow smear at presentation (1975). A. Early polychromatophylic erythroblasts connected by chromatin bridge. X 600. B . Single and binucleate micrornegakaryocytes (arrows). X400.

Case 2 In 1928, this woman, age 30, suffered from menometrorrhagia for which she

was treated with uterine radium implants. In 1955 she developed dysphonia after an upper respiratory infection, for which she was seen in the Mayo Clinic. Blood counts at that time were normal. In 1966 she sought evaluation of weakness, and was found to be mildly anemic (Table 11). She persuaded her physician to treat her with iron and Vitamin B12 which were continued for several months. With no improvement in her hematologic status, the medications were discontinued. In January 1971, at the age of 73, she developed atrial fibrillation and Stokes-Adams episodes. While hospitalized, she was referred to the hematology service, Brooke Army Medical Center, Texas, for evaluation of persistent mild anemia (Table 11).

Laboratory examinations. Blood counts are summarized in Table 11. 51Chromium red cell survival revealed a normal T1/2 of 28 days. Serum BI2 and folate were normal. The serum iron level was 140 pg/dl, the total iron binding capacity was 280 ug/dl, with 50% saturation.

Bone marrow. The first marrow for examination was obtained in 1971 and was of normal cellularity. The M/E ratio was reduced due to erythroid hyperplasia. Dyserythropoietic features, ie, nuclear bridging, binuclearity of erythroblasts, and karyorrhexis, were readily apparent (Fig. 3A,B). Approximately 40 % of megakary- ocytes were dysmorphic, ie, small cells with single or two nuclei, others showing tear-drop-shaped nuclear buds and internuclear chromatin bridges (Fig. 3C ,D). The

318 Case Report:, Bethlenfalvay et a1

Fig. 2. Case 1. Representative field of preterminal bone marrow biopsy section showing atypical megakaryocytes and clusters of undifferentiated cells presumed to be blasts. Dense connective tissue is present. H + E ~ 2 0 0 .

TABLE 11. Laboratory Data of Case 2

1966 1971 1973 1975 1976

Hemoglobin (g/dl) 13.2 12.3 10.4 4.8 7.3 Erythrocytes ( x 10'*/1) 4 4.13 1.57 2.7 Hematocrit (%) 37 36 31 16 23 MCH (pg) 31.5 31 MCHC (g/dl) 35.5 30 MCV (fl) 89 100 95 Reticulocytes (%) 1.4 2.8 3.4 2.6 Anisocytosis ++ ++++ + + Poikiloc ytosis + ++++ ++ Nucleated erythrocytes/100 WBC 1 6 Leukocytes ( x 109/1) 5.7 9.4 3.1 11.5 31.0 Myeloblasts (%) 3 6 Platelets ( x 109/1) 274 198 77 27

myeloid cell lineage was normal, and the iron stain showed normal iron content and distribution.

Cytogenetics. Several marrow metaphase spreads were available for evaluation. All showed a normal female (46-xx) karyotype. The 5q-phenomenon was not ob- served. Every chromosome had a fuzzy and ill-defined boundary of the chromatids.

Clinical course. The remaining 6 years of the patient's life were characterized by a gradually increasing dementia, congestive heart failure, and anemia. Multiple peripheral blood and bone marrow evaluations between 1971 and 1976 revealed

Case Report: Erythroid Nuclear Bridging in Preleukemia 319

Fig. 3 . Case 2. Wright-stained marrow smear at presentation (1971). A. Late polychromatophilic erythroblasts showing binuclcarity and internuclear bridging. ~ 4 0 0 . B. Late polychromatophilic ery- throblasts connected by chromatin bridge. X400. C, D. Dysmorphic megakaryocytes showing nuclear budding and internuclear chromatin bridges. X600.

progressively more profound dyserythropoietic changes; however, internuclear bridg- ing of erythroblasts gradually diminished in numbers and by 1974 was no longer observed. Preterminally marked aniso-poikilocytosis, crenated cells, normoblasts, and myeloblasts were seen in the peripheral blood. The marrow showed increasing numbers of megaloblastoid red cell precursors, giant multinucleated normoblasts, vacuolization of basophilic erythroblasts (Fig. 4A) with chunky positivity on staining with PAS. There was also a progressive increase of myeloblasts and promyelocytes relative to more mature granulocytic elements.

The patient was treated conservatively with blood transfusions and antibiotics when indicated. She expired in December 1976.

Autopsy. The marrow was 100% cellular showing an increase in myeloblasts and immature red cell precursors (Fig. 4B). Sections of the spleen and liver revealed diffuse infiltration by neoplastic myeloid and erythoid elements. There were no abnormalities of the uterus or adnexa on gross and microscopic examination. The final pathologic diagnosis was erythroleukemia.

DISCUSSION

The observation of multinuclearity, chromatin bridges, and megablastoid fea- tures of marrow erythroblasts in an elderly patient with refractory anemia, initially, may present a dilemma in diagnosis. Because of the similarity to the morphologic

320 Case Report: Bethlenfalvay et a1

Fig. 4. Case 2. A. Preterminal marrow smear showing vacuolization of erythroid precursors, rnegalo- blastoid features, and giant polychromatophylic normoblast. X600. B. Section of marrow biopsy showing dense cellularity with a large proportion of myeloblasts and immature red cell precursors. H + E x200.

features seen in the marrow of patients with CDA-I [9-111, our second patient was erroneously diagnosed as a late recognized case of CDA-I [8].

CDA-I is a rare disorder, thought to be transmitted in the autosomal-recessive mode. Anemia or jaundice (or both) are usually first noted in infancy, childhood, or adolescence [9]. In at least three patients, however, the diagnosis of CDA-I was entertained in old age. In two of these cases, light microscopy of the marrow revealed not only internuclear bridging of erythroblasts, but dysmorphysm of the megakary- ocytic lineage as well [8,12]. The marrow erythroblasts in the third case were indistinguishable by electron microscopy from those seen in previously reported younger cases of CDA-I but, in contrast, the megakaryocytes appeared normal [13]. At the time of this writing, this patient is well and hematologically stable 12 years after diagnosis. Phaure’s patient [12] died in 1976 from conditions unrelated to her hemopoietic system, but an autopsy was not performed.

In addition to the abnormalities seen in the erythroid lineages, the marrow of our cases featured abnormalities of megakaryocytes as well (Figs. lB, 3C,D). These resembled the abnormalities described in the smouldering myeloid leukemic state [ 1- 5,7,19] and in the 5q-syndrome [14], now also recognized as a potential preleukemic condition [ 15 , 161. Unfortunately, in our two cases, electron microscopy and karyotyp- ing of hematopoietic tissue of the first case were not available. Nuclear bridging of erythroblasts and megakaryocytic abnormalities were more prominent in the second case, whose marrow chromosomes exhibited the “fuzzy” pattern, also considered to

Case Report: Erythroid Nuclear Bridging in Preleukemia 321

indicate the presence of a leukemic process 1171. In neither case were the myeloid cell lineages involved, when first studied, an observation that is consistent with cases presented in other comprehensive reviews [ 1-61.

Internuclear bridging of erythroblasts is a nonspecific sign of dyserythropoiesis and was, to the best of our knowledge, first described in a case of pernicious anemia and in a case of “anemia of infancy” 1181. It is considered a very rare morphologic phenomenon in the preleukemic state [ 19-21]. Our observations, in addition, suggest that internuclear bridging may be seen only in the early phase of evolution of the preleukemic state. Thus, it may be significant that a recent study of 15 cases of erythroleukemia, including a review of the literature, contains no mention of the observation of nuclear bridging of erythroblasts [22]. Clearly, frequent bone marrow evaluations of more cases suspected to have preleukemia are needed to confirm the validity of our observations.

ACKNOWLEDGMENTS

We are indebted to Prof. Dr. H. Heimpel, University of Ulm, German Federal Republic for his critical reading of the manuscript.

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