Mastocytosis:A disease at the crossroads of hematology and allergology

Mastocytose is een zeldzame ziekte waarbij mensen vanwege kwaadaardige witte bloedcellen last krijgen van klachten die veel overeenkomst hebben met allergische symptomen. In dit proefschrift beschrijven we wat de meest voorkomende klachten zijn: vermoeidheid, jeuk, opvliegers en levensbedreigende allergische reacties op insectensteken. Daarbij beschrijven wij wat de invloed is van al deze klachten op de kwaliteit van leven van mastocytose patiënten en hoe we dit met een tweetal vragenlijsten kunnen mesten. Daarnaast beschrijven we mogelijke methodes om te identificeren welke mastocytose patiënten nu het grootste risico hebben op levensbedreigende reacties op insecten steken en waarom andere patiënten wellicht beschermd zijn hiervoor. Tot slot beschrijven we de invloed van een nieuwe vorm van chemotherapie, genaamd midostaurin, op deze allergische symptomen. Midostaurin lijkt een veilig en relatief effectief middel te zijn om de klachten te verminderen van mastocytose patiënten

Patients with mast cell activation symptoms and elevated baseline serum tryptase level have unique bone marrow morphology

Background: Patients with mast cell (MC) activation symptoms and elevated baseline serum tryptase level (MCAS-T) may not necessarily have a clonal MC disorder. Many are diagnosed with hereditary a-tryptasemia (HaT), a genetic trait characterized by autosomal dominant inheritance of multiple copies of TPSAB1 encoding a-tryptase and increased risk for severe anaphylaxis. Objective: The aim of our study was to identify and characterize bone marrow MC histopathologic features specific for MCAS-T. Methods: A total of 43 patients with MCAS-T underwent evaluation, including bone marrow biopsy, for a MC disorder. The results of the work-up for clonal MC disorders such as systemic mastocytosis and monoclonal MC activation syndrome were negative. Bone marrow MC histopathology was reviewed to identify characteristic features of MCAS-T. A subgroup of patients was available for tryptase genotyping. Results: Patients with MCAS-T showed unique morphologic and histologic features when compared with controls. MCs were larger (P < .01), hypogranular (P < .01), frequently detected in paratrabecular (P < .05) and perivascular (P < .01) locations, and associated with bone marrow eosinophilia (P < .01). A total of 10 patients who were available for tryptase genotyping were all confirmed to have HaT. This subgroup was representative of the larger MCAS-T cohort. Conclusion: We report unique bone marrow MC phenotypic and histopathologic changes in patients with MCAS-T. These morphologic changes are associated with an elevated tryptase level that has been confirmed to be caused by HaT in all patients available for testing. (J Allergy Clin Immunol 2021;147:1497-501.

Fatal Anaphylaxis to Yellow Jacket Stings in Mastocytosis:Options for Identification and Treatment of At-Risk Patients

BACKGROUND: Patients with indolent systemic mastocytosis (ISM) are at risk for severe anaphylactic reactions to yellow jacket (YJ) stings while demonstration of sensitization can be challenging because specific IgE (sIgE) levels are regularly below 0.35 kU(A)/L. The implication of missing YJ allergy is illustrated by a case of fatal anaphylaxis. OBJECTIVE: To explore the natural course of YJ venom allergy and the diagnostic accuracy and therapeutic consequence of YJ venom sIgE in patients with ISM. METHODS: All patients with ISM seen from 1981 to 2015 (n = 243) were evaluated on the number of YJ stings, reaction severity, and sensitivity and specificity of YJ venom sIgE. YJ venom allergic patients without mastocytosis served as control (n = 313). RESULTS: A total of 153 patients with ISM were stung during adult life. The first systemic reaction was more often severe in patients with ISM than in patients without mastocytosis (69.9% vs 22.0%) and reactions recurred in 40 of 41 re-stung patients with ISM. ISM reactors showed lower YJ venom sIgE levels than nonmastocytosis reactors (0.61 vs 4.83 kU(A)/L; P <.001) and asymptomatic sensitization was exceedingly rare. In ISM the current clinical threshold of 0.35 kU(A)/L yields a sensitivity and specificity of 77.6% and 87.5%, respectively. The optimal diagnostic accuracy is achieved at 0.17 kU(A)/L (sensitivity, 83.6%; specificity, 85.0%). CONCLUSIONS: The high rate of severe reactions and the fatal case underscore the importance of adequate diagnostic sensitivity of sIgE in patients with ISM. The sensitivity of sIgE can be ameliorated by lowering the threshold to 0.17 kU(A)/L, retaining good specificity. We recommend sIgE screening in all patients with ISM and discussing immunotherapy when YJ venom sIgE exceeds 0.17 kU(A)/L

Nieuwe ontwikkelingen voor patienten met geavanceerde systemische mastocytose

Geavanceerde systemische mastocytose is een kleine subgroep van ziektebeelden binnen systemische mastocytose (SM), waar vooral hematologen mee te maken krijgen. Tot geavanceerde SM worden agressieve SM, SM met bijkomende hematologische neoplasie (SM-AHN) en mestcelleukemie (MCL) gerekend. De laatste jaren zijn er belangrijke diagnostische, prognostische en therapeutische ontwikkelingen. Behalve de KIT-mutatie blijken vele andere mutaties voor te komen die onder meer prognostisch sterk voorspellend zijn voor de overleving. Na een wereldwijde fase 2-studie waaraan ook vanuit Nederland is geparticipeerd, is midostaurin (onder meer een c-KITblokker) geregistreerd voor deze groep patiënten, omdat er niet alleen veel responsen werden waargenomen, maar er ook overlevingswinst werd behaald. Desalniettemin zijn er geen complete remissies bereikt en zal allogene stamceltransplantatie voor een hoogrisicogroep een belangrijke mogelijkheid zijn. Momenteel wordt binnen Europees verband gewerkt aan nieuwe studies. De verwachting is dat Nederland wederom een belangrijke bijdrage zal leveren

Higher mast cell load decreases the risk of Hymenoptera venom-induced anaphylaxis in patients with mastocytosis

<p>Background: Increased basal serum tryptase (bsT) levels are a well-described risk factor for Hymenoptera venom-induced anaphylaxis (HVAn) in patients allergic to Hymenoptera venom. Increased bsT levels might also indicate the presence of mastocytosis. In this study we evaluated whether the risk of HVAn increases with increasing mast cell load in patients with mastocytosis.</p><p>Methods: Consecutive patients with different subtypes of mastocytosis (n = 329) admitted to the University Medical Center Groningen were retrospectively assessed. As markers for mast cell load, levels of both bsT and the urinary histamine metabolites methylhistamine and methylimidazole acetic acid (MIMA) were used.</p><p>Results: In the entire patient group, irrespective of disease subtype and Hymenoptera venom exposure, HVAn prevalence gradually increased with increasing marker levels to a maximum of 36% to 47% at a bsT level of 28.0 mu g/L, a methylhistamine level of 231.0 mu mol/mol creatinine, and a MIMA level of 2.7 mmol/mol creatinine but decreased thereafter with a further increase in these levels. In patients with indolent systemic mastocytosis with a history of Hymenoptera venom exposure after age 15 years or greater (n = 152), MIMA and age at the most recent Hymenoptera sting were independent predictors for HVAn (odds ratios of 0.723 [P = .001] and 1.062 [P <.001], respectively).</p><p>Conclusions: In patients with mastocytosis, HVAn prevalence does not increase constantly with increasing levels of mast cell load parameters: after a gradual increase to a maximum of near 50%, it decreases with a further increase in these levels. In the indolent systemic mastocytosis population, all mast cell load markers were independent negative predictors of HVAn. These findings suggest a complex pathophysiologic association between mast cell load and HVAn risk in patients with mastocytosis.</p>

CD30 in Systemic Mastocytosis

CD30 is a transmembrane receptor, normally not expressed by mast cells, which regulates proliferation/apoptosis and antibody responses. Aberrant expression of CD30 by mastocytosis mast cells and interaction with its ligand CD30L (CD153) appears to play an important role in the pathogenesis and clinical presentation of systemic mastocytosis. This article highlights the expression profile and role of CD30 and CD3OL in physiologic and pathologic conditions, the applicability of CD30 as a marker for systemic mastocytosis, the consequences of mast cell-expressed CD30, and the possibility of future anti-CD30 based cytoreductive therapies