Mastocytosis – A Disease of the Hematopoietic Stem Cell: In reply

A Disease of the Hematopoietic Stem Cell by Prof. Dr. med. Hans-Peter Horny, Prof. Dr. med. Karl Sotlar, Prof. Dr. med. Peter Valent, PD Dr. med. Karin Hartmann in volume 40/2008

The desire to diagnose mastocytosis with clinical certainty is understandable, but it is not possible in practice because of the overlapping symptoms with the so-called ‘mast cell activation syndrome’ (MAS) mentioned by Molderings et al.

The diagnosis of mastocytosis is based on the generally recognized and precise criteria defined by the WHO, in particular on a finding of a compact mast cell infiltrate by the histopathologist ("major diagnostic criterion"), as well as additional findings that relate to specific morphological phenotypical and molecular changes ("minor diagnostic criteria") of the mast cells in mastocytosis. If these criteria are met then "reactive" mast cell hyperplasia can be excluded, as can disorders "in which healthy mast cells may be highly active".

The concept of diagnosing mastocytoses by combining clinical, morphological, and molecular findings has become the standard approach internationally. It is confirmed not least by the fact that the 2001 WHO classification of mastocytoses has now been included without major modifications in the WHO book on the classification of hematological neoplasias and will thus continue to be applied in all leading centers (1).

The mast cell activation syndrome to date is not a clearly defined diagnosis but always fails to meet the diagnostic criteria of mastocytosis. Initiating unnecessary diagnostic or therapeutic measures under the heading of "mast cell activation" should be avoided. On the other hand, missing staging investigations, especially histological evaluation of the bone marrow in adults and faulty application of the mastocytosis criteria defined in the WHO classification may not only result in misinterpretation of findings in patients with mastocytosis but also runs the risk that other possibly life-threatening hematological disorders are overlooked (2).

We agree that mastocytosis is an underdiagnosed disorder. We should, therefore, all aim to improve this situation by providing information and training, not by extending the definition of the disease as suggested by Molderings et al.. DOI: 10.3238/arztebl.2009.0174


Prof. Dr. med. Hans-Peter Horny
Institut für Pathologie
(Referenzzentrum für Hämatopathologie
im Rahmen des ECNM)
Escherichstr. 6
91522 Ansbach, Germany

Prof. Dr. med. Karl Sotlar
Institut für Pathologie
Ludwig-Maximilians-Universität München
80337 München, Germany

Prof. Dr. med. Peter Valent
Innere Medizin I (Hämatologie)
Universität Wien
1090 Wien, Austria

PD Dr. med. Karin Hartmann
Klinik und Poliklinik
der Abteilung für Dermatologie und Venerologie
Universität Köln, 50937 Köln, Germany


Conflict of interest statement
The authors of the letter and of the reply declare that no conflict of interest exists according to the guidelines of the International Committee of Medical Journal Editors.

References

1. Horny H-P, Akin C, Metcalfe DD: Mastocytosis. In: Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Vardiman JW (eds): WHO classification of tumours of haematopoietic and lymphoid tissues. Lyon: IARC Press 2008.

2. Horny H-P, Sotlar K, Valent P, Hartmann K:Mastocytosis—a disease of the hematopoietic stem cell [Die Mastozytose – Eine Erkrankung der hämopoetischen Stammzelle]. Dtsch Arztebl Int 2008; 105(40): 686–92.