DÄ internationalArchive4/2008Essential Thrombocythemia – Clinical Significance, Diagnosis and Treatment: In Reply

Correspondence

Essential Thrombocythemia – Clinical Significance, Diagnosis and Treatment: In Reply

Dtsch Arztebl Int 2008; 105(4): 72; DOI: 10.3238/arztebl.2008.0072

Griesshammer, M

Prof. Dr. C. Dame reports on the also relevant familial forms of essential thrombocythemia which we have not mentioned for reasons of space. These forms are naturally also to be included in the differential diagnosis.

Dr. Tsamaloukas asks the justified question whether patients with polyclonal ET or polymorphism of the thrombopoietin receptor should be treated differently. Although there is evidence that these patients have a different risk constellation, these constellations have not been included in the risk stratification, with the result that the patients concerned are not treated differently (1). The second question as to which therapeutic modality is capable of reducing the JAK2 mutated clone was answered in a recent publication. However, a reduction of the JAK2 mutated clone is described here only for pegylated interferon-alpha-2a, and only in polycythemia vera (PV) (2). But the molecular response rates do not even approach the magnitudes observed for, e.g., imatinib in CML.

The most recently published WHO criteria also state that bone marrow biopsy is essential for diagnosis of ET (3). Dr. Andreas is right, however, when he says that the conventional PVSG criteria do not state that bone marrow biopsy is mandatory for ET. Making a diagnosis based on the PVSG criteria, however, has the disadvantage that early onset forms of primary myelofibrosis (PMF) or polycythemia (PV) are frequently overlooked and are often erroneously classified as ET. The study of Harrison et al. did indeed describe an increased incidence of myelofibroses after anagrelide therapy. In this connection it should be mentioned that the patient sample in the MRC-PT1 study was a heterogeneous population which was diagnosed not according to the WHO criteria but the PVSG criteria. Follow-up investigations, for example, showed that a majority of these patients had early-onset forms of primary myelofibrosis (PMF) and not ETs. Furthermore, no sequential biopsies were available for most of the patients, and therefore follow up information is limited. The conventional practice of administering aspirin in secondary thrombocytosis is not substantiated with data. An elevated risk of thrombosis is only actually present in individual cases of secondary thrombocytosis (for example with additional malignancies and/or major surgery) (4).

Since ET has a very good prognosis, experimental therapy with JAK2 inhibitors is without primary value in this context. As Dr. Stern rightly inquires, however, these agents are now being used in initial phase I studies in primary myelofibrosis (PMF) and polycythemia vera (PV) after conventional therapy has failed.
DOI: 10.3238/arztebl.2008.0072

Prof. Dr. med. Martin Griesshammer
Klinik für Innere Medizin III
Universitätsklinik Ulm
Robert-Koch-Str. 8
89081 Ulm, Germany
martin.griesshammer@uniklinik-ulm.de

Conflict of interest statement
The authors of all articles declare that no conflict of interest exists according to the guidelines of the International Committee of Medical Journal Editors.
1.
Griesshammer M: Risk factors and their influence on therapeutic decisions in patients with essential thrombocythemia. Semin Thromb Hemost 2006; 32: 372–80. MEDLINE
2.
Kiladjian JJ, Cassinat B, Turlure P et al.: High molecular response rate of polycythemia vera patients treated with pegylated interferon-a alpha-2a. Blood 2006; 108: 2037–40. MEDLINE
3.
Tefferi A, Thiele J, Orazi A et al.: Proposals and rationale for revision of the World Health Organization diagnostic criteria for polycythemia vera, essential thrombocythemia, and primary myelofibrosis: recommendations from an ad hoc international expert panel. Blood 2007; 110: 1092–7. MEDLINE
4.
Griesshammer M, Sauer T, Wenauer H, Bangerter M, Heimpel H: Aetiology and clinical significance of thrombocytosis: Analysis of 732 patients with an elevated platelet count. J Intern Med 1999; 245: 295–300. MEDLINE
1. Griesshammer M: Risk factors and their influence on therapeutic decisions in patients with essential thrombocythemia. Semin Thromb Hemost 2006; 32: 372–80. MEDLINE
2. Kiladjian JJ, Cassinat B, Turlure P et al.: High molecular response rate of polycythemia vera patients treated with pegylated interferon-a alpha-2a. Blood 2006; 108: 2037–40. MEDLINE
3. Tefferi A, Thiele J, Orazi A et al.: Proposals and rationale for revision of the World Health Organization diagnostic criteria for polycythemia vera, essential thrombocythemia, and primary myelofibrosis: recommendations from an ad hoc international expert panel. Blood 2007; 110: 1092–7. MEDLINE
4. Griesshammer M, Sauer T, Wenauer H, Bangerter M, Heimpel H: Aetiology and clinical significance of thrombocytosis: Analysis of 732 patients with an elevated platelet count. J Intern Med 1999; 245: 295–300. MEDLINE

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