Microcytosis in agnogenic myeloid metaplasia: Prevalence and clinical correlates

Leukemia Research 30 (2006) 677–680

Microcytosis in agnogenic myeloid metaplasia: Prevalence and clinical correlates Ayalew Tefferi ∗ , David Dingli, Chin-Yang Li, Ruben A. Mesa Divisions of Hematology and Hematopathology, 200 First Street SW, Mayo Clinic, Rochester, MN 55905, USA Received 14 August 2005; accepted 5 October 2005 Available online 8 November 2005

Abstract Microcytosis is a characteristic laboratory feature for both iron deficiency anemia and thalassemia. It is also infrequently seen in “anemia of chronic disease” that accompanies a spectrum of chronic conditions including rheumatoid arthritis, polymyalgia rheumatica, diabetes mellitus, connective tissue disease, and protracted infection. In addition, there is a well established but pathogenetically obscure association of microcytosis with Hodgkin’s lymphoma, Castleman’s disease, and renal cell carcinoma. In the current study, we show that microcytosis is a frequent laboratory feature in agnogenic myeloid metaplasia and investigate its clinical relevance in the particular setting. © 2005 Elsevier Ltd. All rights reserved. Keywords: Myelofibrosis; Microcytosis; Prognosis; Incidence; Survival

1. Introduction The most frequent cause of microcytosis (mean corpuscular volume of < 80 fL) is iron deficiency anemia (IDA) followed by genetic causes including alpha- and betathalassemia as well as certain structural hemoglobinopathies including hemoglobin E trait/disease [1]. Together, IDA and the thalassemic syndromes account for over 80% of the cases with microcytosis seen in routine clinical practice [2]. Furthermore, the application of modern laboratory methods for detecting alpha-globin gene deletions might increase the particular figure even higher and account for some of the so-called idiopathic cases [3]. Non-thalassemic microcytosis that is not related to IDA is largely attributed to “anemia of chronic disease (ACD; a.k.a. anemia of inflammation)” [4]. The pathogenesis of ACD is not fully understood and both hepcidin and pleiotropic cytokines including interleukin-6 have been implicated [5]. The prevalence of microcytosis in ACD is estimated at 20% and the spectrum of ACDassociated clinical conditions include rheumatoid arthritis, ∗

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polymyalgia rheumatica, diabetes mellitus, connective tissue disease, chronic infection/inflammation, and metastatic cancer [6]. Microcytosis, sometimes marked, is also a well established laboratory feature in a subset of patients with Hodgkin’s lymphoma [7], Castleman’s disease [8], or renal cell carcinoma [9]. The pathogenesis in at least some of the patients with these disorders might involve either unbalanced globin chain synthesis or functional iron deficiency resulting from diversion of iron from erythropoietic to tumor tissue [7,9]. Other rare causes of microcytic anemia include aluminium toxicity [10], hypocupremia [11], and the pyridoxine-sensitive X-linked sideroblastic anemia that is associated with mutations of the erythroid-specific delta-aminolevulinate synthase gene [12]. In the current communication, we report a relatively high prevalence of microcytosis in agnogenic myeloid metaplasia (AMM), a clonal stem cell disorder that is characterized by progressive anemia, hepatosplenomegaly from extramedullary hematopiesis, and bone marrow histological changes that include collagen fibrosis, osteosclerosis, and angiogenesis [13]. We also demonstrate that AMM-associated microcytosis is not prognostically relevant.

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A. Tefferi et al. / Leukemia Research 30 (2006) 677–680

2. Methods The current retrospective study was approved by the Institutional Review Board of the Mayo Clinic, and Minnesota and HIPAA guidelines regarding access to medical records were followed. Diagnosis of AMM was according to standard World Health Organization criteria [14]. The current study did not include patients with either post-polycythemic or post-thrombocythemic myeloid metaplasia. Bone marrow histology in all cases was reviewed by Mayo Clinic hematopathologists and re-reviewed by one of the authors (CYL). For cytogenetic studies, both direct technique and un-stimulated 24-h culture methods were used to harvest 20 metaphases, whenever possible, in all bone marrow specimens [15]. In order to minimize the confounding effects of nutritional deficiencies, red blood cell transfusion, and drug therapy on mean corpuscular volume (MCV), the current study was limited to young patients (age < 60 years) that had not received either red blood cell transfusion or drug therapy for MMM during the time of their initial laboratory investigation. For the purposes of the current communication, we followed previously published criteria to define microcytosis as an MCV of < 80 fL. The Mayo Clinic normal MCV reference range for adult males is 81.2–95.1 and for females 81.6–98.3. Statistical analysis was performed using SAS software (SAS, Inc., Cary, NC). Comparison between categorical variables was performed by Chi-squared statistics. Comparison between categorical and continuous variables was performed by either the Mann–Whitney U-test or Kruskal–Wallis test. Survival was calculated by Kaplan–Meier plots taking the interval from the date of diagnosis to death or last contact and checked for significance by both the Logrank test. A Cox proportional hazards regression analysis was used to assess the prognostic relevance, to survival, of key prognostic variables including microcytosis.

3. Results 3.1. Presenting clinical features The study population consisted of 102 consecutive patients with AMM (median age 51 years, range 18–60) including 60 males and 42 females. At diagnosis, the median (range) values for hemoglobin, leukocyte count, and platelet count were 11 g/dL (7.4–14.9), 8.3 × 109 /L (1–40) and 357 × 109 /L (14–1512), respectively. Spleen measurements were documented in 78 patients (median 6 cm below the left costal margin, range 0–24) and the incidence of hypercatabolic symptoms was 18% (12 of 67 evaluable patients). Median LDH, available in 47 patients, was 359 U/L. Normal LDH reference range at our laboratory is 94–257 U/L. Twenty-three patients (23%) displayed a hemoglobin level of < 10 g/dL, 17 patients (17%) a leukocyte count of either < 4 or > 30 × 109 /L, and another 17 patients (17%) a platelet count of < 100 × 109 /L. The Dupriez prognostic score distri-

bution included low-risk (n = 73), intermediate-risk (n = 19), and high-risk (n = 10) disease categories. The overall incidence of microcytosis (MCV < 80 fL) was 28%; median MCV was 84.3 fL (range, 60.6–99.1) The median (range) MCV in patients with microcytosis and those without microcytosis were 76.7 (60.6–79.9) and 86 (80–99.1), respectively. Among the 28 patients with microcytosis, MCV was less than 70 fL in 4 patients. Concomitant serum ferritin levels were available in 44 patients (median, 92 ␮g/L; range, 4–6440) and the levels were below 30 ␮g/L in seven patients including four patients with microcytosis. Serum ferritin levels were available in three of the four patients with an MCV of < 70 fL and were 60.6, 63.1, and 256 ␮g/L. The distribution of ferritin levels in all 44 patients was below 20 ␮g/L in seven patients, between 20 and 50 ␮g/L in eight patients, 50–100 ␮g/L in eight patients, 100–300 ␮g/L in 16 patients, and above 300 ␮g/L in five patients. 3.2. Clinical course The study cohort was followed for a median of 70 months (range 0–300). Median survival was 105 months. The relatively long median survival was expected in the current cohort of young patients that were not transfusion dependent at the time of diagnosis. Multivariate analysis of variables that were measured in all study patients identified a hemoglobin level of < 10 g/dL (p = 0.001), platelet count of < 100 × 109 /L (p = 0.0001), and older age (p = 0.02), but not MCV (p = 0.3 as a continuous variable and 0.23 as a categorical variable with a demarcation point of 80 fL), as independent prognostic indicators of inferior survival (Fig. 1). The addition of variables that were measured in a variable proportion of the study population, to the above multivariate model, disclosed additional prognostic value for hypercatabolic symptoms and abnormal cytogenetics. Despite the lack of prognostic relevance, microcytosis was significantly associated with the absence of cytogenetic abnormalities (p = 0.04). Among 40 patients in whom cytogenetic studies were available, clonal abnormalities were documented in 10 (25%) and the MCV was ≥ 80 in all but one of these 10 patients (p = 0.04). In the single patient

Fig. 1. Overall survival of patients with agnogenic myeloid metaplasia stratified by the mean corpuscular volume (MCV).

A. Tefferi et al. / Leukemia Research 30 (2006) 677–680

with microcytosis and abnormal cytogenetic findings, the MCV was 77 fL and the specific cytogenetic abnormality del(7)(pl5). On the other hand, microcytosis did not correlate with several other clinical and laboratory features including age (p = 0.43), gender (p = 0.64), presence of hypercatabolic symptoms (p = 0.52), spleen size (p = 0.27), hemoglobin level (p = 0.85), platelet count (p = 0.76), leukocyte count (p = 0.18), serum lactate dehydrogenase level (p = 0.39), degree of bone marrow fibrosis (p = 0.47), and the Dupriez prognostic score (p = 0.31).

4. Discussion The current study establishes microcytosis as one of the relatively frequent laboratory features of AMM occurring in approximately a quarter of the patients. Iron deficiency is documented in a minority of such patients and in general there is no significant correlation between the MCV and serum ferritin level (p = 0.25). The degree of AMM-associated microcytosis might be marked (i.e. MCV < 70 fL) and the current study documents four such cases; three of them had a serum ferritin level that was either normal or elevated. Whether or not AMM-associated microcytosis represents an acquired defect of globin synthesis, as might be the case in some patients with myelodysplastic syndrome (MDS), [16] remains to be elucidated. In this regard, it is to be recalled that some patients with MDS display an abnormal globin chain ratio that appears to be prognosis-neutral [17] as well as a prognostically relevant increase in hemoglobin F concentration [18]. Most recently, MDS-associated microcytic anemia was linked to acquired alpha-thalassemia whose pathogenesis might involve either deletion of the alpha-globin gene cluster or ATRX mutations that cause down-regulation of alpha-globin gene expression [16]. The occurrence of microcytic indices in patients with AMM had been recognized as early as 1981 [19]. The particular study involved four patients with normal alpha/beta globin synthetic ratio. On the other hand, acquired hemoglobin H disease has also been reported in a patient with AMM [20]. Therefore, there is probably more than one pathogenetic mechanism for microcytosis that is associated with both AMM and MDS. An alternative explanation for AMM-associated microcytosis hinges on the observation that iron is primarily taken by the spleen during extramedullary hematopoiesis and is thus diverted from the bone marrow with subsequent functional iron deficiency [21]. A similar mechanism of red cell iron deprivation in the presence of adequate iron stores has been implicated in hypernephroma-associated microcytic anemia where iron is preferentially stored in tumor tissue [9]. If the particular hypothesis is true, then it provides a potential mechanism of effect for splenectomy-associated alleviation of anemia in AMM [22]. However, we believe that the latter treatment effect is probably related for the major part on alleviation of splenic sequestration. Regardless, the results of the current study do not attach prognostic relevance to micro-

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cytosis in patients with AMM. In future studies, it would be interesting to explore the effect of microcytosis on treatment response, especially in patients receiving erythropoietin therapy [23]. Finally, the observation regarding the low incidence of cytogenetic abnormalities in AMM patients with microcytosis is intriguing but requires validation by a prospective study.

Acknowledgments There are no potential author conflicts of interest that relate to the current manuscript. Contributions: Ayalew Tefferi designed the study, contributed patients, abstracted clinical data, performed the statistical analysis, and wrote the paper. David Dingli participated in the design of the study, contributed patients, abstracted clinical data, participated in the statistical analysis of data, and approved the final draft of the manuscript. Chin-Yang Li participated in the design of the study, reviewed all pathology specimens, and approved the final draft of the manuscript. Ruben Mesa participated in the design of the study, contributed patients, and approved the final draft of the manuscript.

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