Diagnosis and treatment of thrombocythemia in myeloproliferative disorders.

Myeloproliferative disorders originate in the clonal expansion of a transformed pluripotential hematopoietic progenitor cell. This results in a group of syndromes that include polycythemia vera, essential thrombocythemia, chronic myelocytic leukemia, and agnogenic myeloid metaplasia. Diagnostic criteria forpolycythemia vera and essential thrombocythemia were codified by the Polycythemia Vera Study Group in 1967 and 1977. Subsequent modifications include criteria for evidence of clonal proliferation by abnormal bone marrow karyotype and demonstration of erythropoietin-independence of erythropoiesis or reduced serum erythropoietin. Phlebotomy is the mainstay of treatment for polycythemia vera. The defining characteristic of essential thrombocythemia is a sustained elevation of the platelet count above 600,000/microL in an untreated patient. Symptoms and risk factors are the main determinants of treatment options for patients with essential thrombocythemia. High-risk patients are candidates for cytoreduction, whereas lower-risk patients receive either no treatment, low-dose aspirin, or another antithrombotic therapy. The availability of newer nonleukemogenic and megakaryocyte-specific agents warrants a reassessment of current treatment options.

Current management in polycythemia vera.

Myeloproliferative diseases (MPD) include polycythemia vera (PV), essential thrombocythemia, agnogenic myeloid metaplasia, and chronic myelogenous leukemia. The focus of this report is on PV, which is characterized by an increase in red blood cells, granulocytes, and platelets. Complications associated with PV are an increased risk of thrombosis and abnormal bleeding. Phlebotomy to a hematocrit less than 45% is the mainstay of treatment for erythrocythemia, but may further increase the platelet count, necessitating the use of a platelet-lowering agent in conjunction with phlebotomy. Other treatment strategies include low-dose aspirin or other antithrombotic therapy and cytoreduction. Mounting evidence of the leukemogenicity and mutagenicity of radioactive phosphorus and alkylating agents, as administered using "conventional" regimens, has restricted the liberal use of these treatments. Three drugs have emerged as useful because of their efficacy in reducing the elevated platelet count: anagrelide, hydroxyurea (HU), and interferon alfa (IFN). It is clear that no single agent satisfies all the needs for cytoreduction that arise during the course of PV. Future protocols should be designed that draw on the large body of experience already gained with these drugs to transcend the limitations of single-agent therapy and to improve quality of life as well as survival. Semin Hematol 38(suppl 2):25-28.

Historical perspective on the treatment of essential thrombocythemia and polycythemia vera.

Since 1970, the treatment of essential thrombocythemia (ET) and polycythemia vera (PV) has evolved from alkylating agents to hydroxyurea (HU), and more recently to agents such as interferon-alpha (IFN) and anagrelide. While the earlier treatments for ET and PV have been successful in varying degrees, diagnosis of these disorders is being made earlier and in populations deemed at lower risk, but who may suffer greatly from the toxicity of long-term treatment with these agents. Thus, the risks and benefits of treatment versus nontreatment and between types of therapy have created a need for treatments that are safer for more people for greater lengths of time.

Long term treatment of myeloproliferative disease with interferon-alpha-2b: feasibility and efficacy.

BACKGROUND: Recombinant interferon-alpha-2b (rIFN-alpha-2b) has shown therapeutic potential in patients with chronic myelogenous leukemia and other myeloproliferative disorders (MPDs), including the ability to suppress the abnormal hematopoietic clone and to reverse myelofibrosis. This study was conducted to evaluate further the efficacy and safety of rIFN-alpha-2b in a large group of patients with polycythemia vera, essential thrombocythemia, or agnogenic myeloid metaplasia and to determine maintenance of response after treatment discontinuation. METHODS: Induction therapy began with subcutaneous rIFN-alpha-2b at 5.0 x 10(6) IU/day until a complete or partial response was achieved. Treatment continued at 2.5 x 10(6) IU/day until spleen size and hematologic parameters stabilized. RESULTS: Fifty-four patients were studied (median follow-up, 7.3 years); at last follow-up 27 patients still were participating (median follow-up, 3.8 years). Twenty-four of 24 patients with thrombocythemia (100%) and 14 of 14 patients with hyperleukocytosis (100%) responded to induction therapy, whereas 26 of 39 patients (67%) experienced > 10% decrease in splenomegaly. Thirty-nine of 54 patients (72%) maintained response for a median of 39 weeks after withdrawal of rIFN-alpha-2b; repeat courses in previously responding patients produced similar results. The survival rate at 8 years was 60%. rIFN-alpha-2b generally was well tolerated, but toxicity caused treatment withdrawal in 7 patients (13%). CONCLUSIONS: rIFN-alpha-2b can produce regression of splenomegaly and control of leukocyte and platelet counts in patients with MPD. These responses are sustained for prolonged periods in some patients after therapy discontinuation. In patients with recurrent disease, disease control can be attained again with reinitiation of rIFN-alpha-2b. Therefore this therapy should be an important treatment consideration for patients with MPD.

Familial myeloproliferative disease.

The occurrence of one or more myeloproliferative disease (MPD) syndromes in 42 families is described. MPD appeared in a single generation in 10 families, two generations in 30 families and three generations in two families. In contrast to sparse case reports of familial polycythaemia vera, familial essential thrombocythaemia, or familial agnogenic myeloid metaplasia, in which all the involved members presented with the same MPD, 21 of the 42 families in the present series had members who presented with different MPD variants. The occurrence of multiple disease phenotypes in 'MPD families' is entirely consistent with the accepted theory of MPD as a disease arising from clonal expansion of a pluripotential haematopoietic precursor cell (PHPC) that retains its pluripotentiality and produces an array of inter-related syndromes, each named for the predominant haematic cell type involved in the proliferation. Changes in disease phenotype during the course of MPD and 'hybrid' phenotypes at the time of diagnosis are common. This report challenges the previously accepted belief that PV and other MPD variants are sporadic and randomly-occurring, and that familial occurrence of MPD is rare. The ability to identify 'MPD families' by surveying a large population of patients with MPD through the Internet, as was done in this study, and heightened awareness of familial occurrence and its phenotypic heterogeneity, should facilitate further characterization of the mode of inheritance in familial MPD and the nature of the gene mutations responsible for the dysregulation of haematopoiesis.

Polycythaemia vera. III. Burst-forming units-erythroid (BFU-E) response to stem cell factor and c-kit receptor expression.

We previously demonstrated that highly purified normal human blood burst-forming units-erythroid (BFU-E) need the direct action of recombinant human stem cell factor (rSCF) in the presence of recombinant human erythropoietin (rEP) and recombinant human interleukin-3 (rIL-3) for further development in a serum-free medium. To study the response of polycythaemia vera (PV) BFU-E to rSCF, we performed dose-response experiments in a serum-free medium using highly purified BFU-E from PV patients. A marked increase in the number of PV bursts occurred with increasing concentrations of rSCF, compared to normal burst formation, when the cells were cultured in the presence of rIL-3 at 1 U/ml. The percentage of maximum growth for normal BFU-E was 31 +/- 11% while for PV it was 64 +/- 9% at the highest concentration of rSCF (P < 0.01). Without rIL-3, only 11% of maximum normal BFU-E growth occurred as the rSCF concentration was increased and the size of the colonies was very small, but PV BFU-E still expressed 48% of the maximum number of large erythroid bursts (P < 0.001). This demonstrated an enhanced sensitivity of PV BFU-E to rSCF, compared to normal BFU-E. The pattern of 59Fe incorporation into haem after 8 d of cell culture indicated that PV BFU-E had a time course of maturation and a degree of cellular maturity similar to normal BFU-E. The percentage positivity and intensity of c-kit receptors on PV erythroid cells were examined using immunofluorescence flow cytometry. When BFU-E, CFU-E, or erythroblasts were incubated with phycoerythrin-conjugated SR-1 anti-c-kit receptor monoclonal antibody, 90% of the PV and normal BFU-E displayed c-kit receptor at comparable intensities, as well as 80% of the PV and normal CFU-E. A distinct loss of c-kit expression occurred with erythroid differentiation beyond the CFU-E stage, but at all stages no difference of c-kit receptor expression was evident for PV erythroid precursors compared to normal precursors. These results indicate that the hypersensitivity to rSCF did not appear to be related to the number of c-kit receptors. Since we have previously shown that highly purified PV BFU-E are hypersensitive to rIL-3 and rGM-CSF, as well as rEP, it is now evident that PV BFU-E are hypersensitive to each of the cytokines that have a prominent role in guiding their normal proliferation and differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Polycythemia vera. II. Hypersensitivity of bone marrow erythroid, granulocyte-macrophage, and megakaryocyte progenitor cells to interleukin-3 and granulocyte-macrophage colony-stimulating factor.

Polycythemia vera (PV) is a clonal disease of the hematopoietic stem cell characterized by a hyperplasia of marrow erythropoiesis, granulocytopoiesis, and megakaryocytopoiesis. We previously reported that highly purified PV blood burst-forming units-erythroid (BFU-E) are hypersensitive to recombinant human interleukin-3 (rIL-3). Because these cells may be only a subset, and not representative of marrow progenitors, we have now studied partially purified marrow hematopoietic progenitor cells. Dose-response experiments with PV marrow BFU-E showed a 38-fold increase in sensitivity to rIL-3 and a 4.3-fold increase in sensitivity to recombinant human erythropoietin (rEpo) compared with normal marrow BFU-E. In addition, PV marrow colony-forming units-granulocyte-macrophage (CFU-GM) and CFU-megakaryocyte (CFU-MK) also showed a marked hypersensitivity to rIL-3 and to human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Dose-response curves with rGM-CSF and blood BFU-E showed a 48-fold increase in sensitivity. No effect of rIL-4, rIL-6, human recombinant granulocyte-CSF (rG-CSF), or macrophage-CSF (rM-CSF) was evident, nor was there any effect of PV cell-conditioned medium on normal BFU-E, when compared with normal cell-conditioned medium. Autoradiography with 125I-rEpo showed an increase in Epo receptors after maturation of PV BFU-E to CFU-E similar to that shown with normal BFU-E, but no increase of specific binding of 125I-rIL-3 by PV CD34+ cells was seen compared with normal CD34+ cells. These studies show that PV marrow hematopoietic progenitor cells are hypersensitive to rIL-3 and rGM-CSF, similar to PV blood BFU-E. While the mechanism does not appear to be due to enhanced binding of rIL-3, the hypersensitivity of PV progenitor cells to IL-3 and GM-CSF may be a key factor in the pathogenesis of PV.

Immunoglobulin-related amyloidosis presenting as recurrent isolated lymph node involvement.

Up to 37% of cases of generalized primary and secondary amyloidosis demonstrate lymph node involvement. Lymph node involvement as the presenting feature of generalized amyloidosis is uncommon. Isolated lymph node amyloidosis (that is, with no extranodal amyloidosis) is exceedingly rare; review of the literature reveals only two reported cases. A case of recurrent isolated lymph node amyloidosis is presented, with review of the literature.

Polycythemia vera blood burst-forming units-erythroid are hypersensitive to interleukin-3.

Because polycythemia vera (PV) is a clonal hematopoietic stem cell disease with a trilineage hyperplasia, and interleukin-3 (IL-3) stimulates trilineage hematopoiesis, we have studied the response of highly purified PV blood burst-forming units-erythroid (BFU-E) to recombinant human IL-3 (rIL-3). Whereas the growth of normal blood BFU-E in vitro rapidly declined by 40 and 60% after 24 and 48 h of incubation without 50 U/ml of rIL-3, the growth of PV BFU-E declined by only 10 and 30% under the same conditions, demonstrating a reduced dependence on rIL-3. A reduced dependence of PV BFU-E on recombinant human erythropoietin (rEP) was also present. Dose-response experiments showed a 117-fold increase in PV BFU-E sensitivity to rIL-3, and a 6.5-fold increase in sensitivity to rEP, compared to normal BFU-E, whereas blood BFU-E from patients with secondary polycythemia responded like normal BFU-E. Endogenous erythroid colony (EEC) formation, which is independent of the addition of rEP, was reduced by 50% after erythroid colony-forming cells were generated from PV BFU-E in vitro without rIL-3 for 3 d, whereas rEP-stimulated erythroid colonies were unaffected. These studies demonstrate a striking hypersensitivity of PV blood BFU-E to rIL-3, which may be the major factor in the pathogenesis of increased erythropoiesis without increased EP concentrations.

Erythropoietin receptors in polycythemia vera.

The role of erythropoietin (EP) in polycythemia vera (PV) is controversial, with some experiments suggesting that erythroid progenitors in PV are exquisitely sensitive to EP and EP dependent, and others suggesting that PV progenitors are EP independent. We have examined the characteristics of the EP receptor (EP-R) on erythroid colony-forming cells (ECFC) from patients with PV. In contrast to normal ECFC, which have two classes of EP-R, with 20% showing high affinity (Kd = 0.13 nM; range, 0.04-0.20 nM) and the remainder lower affinity (Kd = 0.37 nM; range, 0.28-0.57 nM), PV ECFC show a single class of 851 low affinity EP-R with Kd = 0.72 nM (range, 0.36-0.85 nM). ECFC from patients with secondary (EP driven) polycythemia or anemia show two classes of EP-R (Kd = 0.18 and 1.10 nM, respectively). Attempts to remove tightly bound EP from putative high affinity EP-R in PV did not reveal any higher affinity receptors. Determination of molecular size by crosslinking showed two proteins of 90 and 100 kD similar to those seen with normal EP-R. These studies indicate the PV ECFC have EP-R that are structurally similar to normal EP-R but lack the higher binding affinity for EP.

Increased circulating CSF-1 (M-CSF) in myeloproliferative disease: association with myeloid metaplasia and peripheral bone marrow extension.

Myeloproliferative disease (MPD) is heterogeneous in phenotypic expression and may display features consistent with expansion and activation of the monocyte/macrophage population during its course. The role of colony-stimulating factor-1 (CSF-1) in the pathophysiology of MPD was investigated by measuring circulating CSF-1 levels and examining their relationship to disease phenotype. Serum CSF-1 concentrations, measured by radioimmunoassay, were elevated in all MPD phenotypes. CSF-1 levels differed significantly between groups of patients with essential thrombocythemia, polycythemia vera, and postpolycythemic or agnogenic myeloid metaplasia (in ascending order). CSF-1 serum levels were positively correlated with spleen size and the degree of peripheral bone marrow extension, determined by scintigraphy using a macrophage-seeking isotope. There was no correlation between CSF-1 concentration and circulating levels of erythrocytes, neutrophils or platelets, or the presence of bone marrow fibrosis. Elevated serum CSF-1 levels appear to be associated with an expanded monocyte/macrophage population in MPD. In view of the known cooperativity between CSF-1 and other growth factors in regulating hematopoiesis, the finding of increased serum CSF-1 concentrations and its association with myeloid metaplasia and bone marrow extension may indicate a pathophysiologic role for CSF-1 in determining the phenotypic expression of MPD.

High-density lipoprotein cholesterol is reduced in patients with sarcoidosis.

PURPOSE: Sarcoidosis is a disease in which the proliferation of monocyte-macrophage-derived cells is observed. In other diseases characterized by expansion of the monocyte-macrophage system, such as Gaucher's disease and myeloid metaplasia, abnormalities of lipoprotein metabolism have been demonstrated. To determine whether similar abnormalities in lipoprotein cholesterol concentrations could be identified in patients with sarcoidosis, we studied total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol as well as triglyceride levels in 52 patients with biopsy-proven sarcoidosis. PATIENTS AND METHODS: Patients had no other medical disorders and were not being treated with corticosteroids or antimalarial agents. Blood samples were collected by venipuncture after an overnight fast. Plasma total cholesterol and triglyceride levels were measured using enzymatic techniques. Lipoprotein cholesterol was quantified by lipoprotein fractionation. HDL cholesterol was measured as cholesterol remaining in the supernatant after precipitation of LDL and very-low-density lipoprotein from whole plasma by the heparin-maganese chloride method. Computation was used to determine the level of LDL cholesterol. RESULTS: We found significantly reduced levels of total cholesterol (183.9 +/- 27.6 versus 194.3 +/- 16.5 mg/dl, mean +/- SD, p = 0.021) and HDL cholesterol (41.2 +/- 13.0 versus 51.9 +/- 6.1 mg/dl, p = 0.0001) in sarcoid patients versus an age-, sex-, and race-matched reference group. Differences were not observed in triglyceride or LDL cholesterol levels (p greater than 0.05). CONCLUSION: These findings are similar to those observed in the myeloproliferative diseases, Gaucher's disease, and rheumatoid arthritis and suggest a functional role for monocytes-macrophages in the regulation of serum lipoprotein cholesterol levels.

Low-density lipoprotein (LDL) distribution shown by 99mtechnetium-LDL imaging in patients with myeloproliferative diseases.

STUDY OBJECTIVE: To image and identify by noninvasive methods the sites of low-density lipoprotein (LDL) catabolism in patients with myeloproliferative disease in whom chronic hypocholesterolemia was previously reported. STUDY DESIGN: The 99mTechnetium-LDL (Tc-LDL) distribution in patients with myeloproliferative diseases was compared with that in normal subjects. The Tc-LDL distribution was also compared with the distribution and organ uptake of a macrophage-seeking radiotracer. 99mTc-sulfur colloid (Tc-SC). SETTING: Major metropolitan referral center and institutional practice. PATIENTS: Three normal subjects, two patients with polycythemia vera, two with post polycythemia myeloid metaplasia, and one with agnogenic myeloid metaplasia. The patients were being managed with hydroxyurea or phlebotomy. INTERVENTION: Ten mCi of Tc-LDL (homologous) was injected intravenously. MEASUREMENTS AND MAIN RESULTS: Gamma camera images of Tc-LDL biodistribution and organ uptake were obtained 4 hours after injection of the tracer. In normal subjects, the Tc-LDL was predominantly taken up by the liver, with relative nonvisualization of spleen and central or peripheral marrow. Patients with myeloproliferative disease showed marked splenic uptake of Tc-LDL. Peripheral bone marrow uptake extended to the lower tibia in two patients with post-polycythemia myeloid metaplasia. Splenic and bone marrow uptake paralleled that of Tc-SC. Hypercellularity of central and peripheral marrow at the sites of Tc-LDL uptake was confirmed by biopsy specimens. The Tc-LDL uptake, however, was not correlated with collagen fibrosis. CONCLUSIONS: These results indicate that spleen and bone marrow are sites of LDL catabolism in patients with myeloproliferative disease and suggest the role of macrophages in the hypocholesterolemia and accelerated LDL catabolism of myeloproliferative disease.

Comparison of erythroid progenitor cell growth in vitro in polycythemia vera and chronic myelogenous leukemia: only polycythemia vera has endogenous colonies.

The ability of erythroid cultures to distinguish among myeloproliferative disorders was examined. We studied 14 patients with polycythemia vera (PV), 11 with chronic myelogenous leukemia (CML), four with non-PV erythrocytosis, two with agnogenic myeloid metaplasia, as well as three normal fetuses and greater than 25 normal adults. Endogenous, i.e. grew without added erythropoietin, bone marrow CFU-E-derived colonies were observed in all but one PV patient. However, endogenous blood BFU-E-derived bursts were observed in only eight of 14 PV patients. Endogenous erythroid colonies were not seen in cultures from any normal adults or fetuses, or patients with CML, erythrocytosis, or myeloid metaplasia. In PV, relative HbF synthesis was always greater in cultures without erythropoietin, while in cultures from all other patients relative HbF synthesis was similar to that observed in cultures from normal individuals. We conclude that PV and CML are distinguishable in culture since CML patients do not have endogenous growth. Most important, endogenous bone marrow CFU-E-derived colonies are the only consistently unique observation in patients with PV, and endogenous CFU-E- and BFU-E-derived colonies and bursts are not uniformly observed in PV blood cultures. In-vitro studies of erythropoiesis to confirm the diagnosis of PV, therefore, require marrow when endogenous colonies and bursts are absent from blood cultures.

Altered high density lipoprotein metabolism in patients with myeloproliferative disorders and hypocholesterolemia.

Patients with the myeloproliferative disorders (MPD), myeloid metaplasia and polycythemia vera, have significantly reduced concentrations of plasma low density (LDL) and high density (HDL) lipoprotein cholesterol (C). We have previously demonstrated that increased catabolism of LDL was associated with the low LDL-C levels. In the present study we have determined the rates of synthesis and removal of apolipoprotein A-1 (apoA-1) in five subjects with MPD who had markedly reduced HDL-C concentrations (18.2 +/- 4.1 mg/dL). Their results were compared to those obtained in six subjects with hypertriglyceridemia (HTG) with similar levels of HDL-C (19.7 +/- 3.9 mg/dL) and five subjects with normal (N) HDL-C concentrations (49.6 +/- 7.4 mg/dL). The results demonstrated that the fractional catabolic rate (FCR) for apoA-1 was significantly increased in the MPD group v N (0.38 +/- 0.15 v 0.21 +/- 0.03 day-1, P less than 0.05) while the synthetic rates for apoA-1 were similar in the two groups. The FCR for apoA-1 in the HTG group (0.36 +/- 0.07 day-1) was nearly identical to that in the MPD group, in spite of the large differences in their plasma triglyceride concentrations (406.2 +/- 217.9 v 117.0 +/- 29.8 mg/dL, P less than 0.05). Compositional studies indicated that the HTG group had very cholesterol depleted HDL while the HDL particles in the MPD group appeared to have a normal cholesterol content. These studies indicate that subjects with MPD have striking increases in HDL catabolism that can account fully for their markedly reduced levels of HDL cholesterol. The pathophysiologic mechanisms that are the basis of this alteration remain to be determined.

Myeloproliferative disorders.

Myeloproliferative disorders result from monoclonal proliferation of the pluripotential hematic precursor cell, with preservation of its capacity to differentiate and mature into functional progeny. Phenotypic expression varies with the degree of involvement of each derivative cell type and the extent to which growth is hyperplastic, dysplastic, or malignant. Hyperplastic bone marrow with increased circulating erythrocytes and platelets, reactivation of hematopoiesis in long bones and extramedullary sites, and the development of secondary marrow fibrosis are responsible for complications of thrombosis, hemorrhage, splenic infarction, hypersplenism, and anemia. A predilection for the geriatric population, chronicity, and great variability in phenotypic expression present a challenge in diagnosis and management. Individualized treatment based on thorough understanding of the pathophysiology of myeloproliferative disease is required to maximize complication-free survival by avoiding both the risk of the disease and its therapy and utilizing all available supportive measures in the prevention and treatment of complications.

The effect of hydroxyurea on hemoglobin F in patients with myeloproliferative syndromes.

Fetal hemoglobin (Hb F) may increase in patients receiving chemotherapeutic drugs, a result of potential use in patients with symptomatic hemoglobinopathies. We examined Hb F in 13 patients with myeloproliferative disease (six polycythemia vera, five polycythemia vera with myeloid metaplasia, one agnogenic myeloid metaplasia, and one chronic myelogenous leukemia) who were treated with hydroxyurea. Four patients showed an increase in Hb F from less than 1% to between 5% and greater than 8% while on hydroxyurea, and a decline to less than 1% when the drug was discontinued. This group of "responders" received a higher average daily dose of hydroxyurea, which was administered continuously rather than intermittently, when compared to the "nonresponders." Mean corpuscular volumes (MCVs) rose in most patients, and i antigen remained elevated or decreased; neither parameter correlated with Hb F levels. Both responders and nonresponders had therapeutically desirable suppression of WBCs and platelets, and almost all had no depression of reticulocytes or Hb.