Serum tryptase levels in patients with mastocytosis: correlation with mast cell burden and implication for defining the category of disease.
BACKGROUND
The serum tryptase level is used as a diagnostic marker in mastocytosis and is considered to reflect the burden of (neoplastic) mast cells (MC).


METHODS
In the present study, serum tryptase levels were measured in patients with mastocytosis by fluoroenzyme immunoassay and compared with the extent of infiltration of the bone marrow (BM) by neoplastic MC, determined by tryptase immunohistochemistry. Sixteen patients with cutaneous mastocytosis (CM) and 43 patients with systemic mastocytosis (SM) were examined.


RESULTS
In most patients with CM (defined by the absence of dense compact MC infiltrates in tryptase-stained BM sections), normal or near-normal serum tryptase levels (median 10 ng/ml, range 2-23 ng/ml) were measured. By contrast, in the vast majority of patients with SM, elevated serum tryptase levels (median 67 ng/ml) were found. In addition, there was a significant correlation between the grade of infiltration of the BM by neoplastic MC and tryptase levels in patients with SM (r = 0.8). Moreover, enzyme levels differed significantly among the groups of patients with different types of SM. The highest levels (>900 ng/ml) were detected in the patient with MC leukemia, 2 patients with slowly progressing SM and high MC burden (smoldering SM) and 1 patient with indolent SM. In contrast, in all 3 patients with isolated BM mastocytosis (no skin lesions and no signs of multiorgan involvement), serum tryptase levels were <20 ng/ml.


CONCLUSIONS
In summary, our data suggest that the measurement of serum tryptase is a reliable noninvasive diagnostic approach to estimate the burden of MC in patients with mastocytosis and to distinguish between categories of disease.
Sperr
Wolfgang R
WR
Department of Internal Medicine I, Division of Hematology and Hemostaseology, University of Vienna, Austria. wolfgang.r.sperr@univie.ac.at
Jordan
John-Hendrik
JH
Fiegl
Michael
M
Escribano
Luis
L
Bellas
Carmen
C
Dirnhofer
Stephan
S
Semper
Hans
H
Simonitsch-Klupp
Ingrid
I
Horny
Hans-Peter
HP
Valent
Peter
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D001706:Biopsy; D001853:Bone Marrow / Q000276:immunology / Q000473:pathology; D019046:Bone Marrow Neoplasms / Q000175:diagnosis / Q000201:enzymology* / Q000378:metabolism; D002648:Child; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008407:Mast Cells / Q000201:enzymology / Q000276:immunology* / Q000473:pathology; D008415:Mastocytosis / Q000201:enzymology* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012697:Serine Endopeptidases / Q000097:blood*; D018709:Statistics, Nonparametric; D053802:Tryptases
D012697:Serine Endopeptidases; D053802:Tryptases