Mastocytosis and related entities: a practical roadmap.

Mastocytosis is a complex heterogenous multisystem disorder that is characterized by pathologic activation or accumulation of neoplastic mast cells (MCs) in one or more organs. This clonal MC expansion is often associated with a somatic gain-of-function mutation (D816V in most of the cases) in the KIT gene, encoding for the MC surface receptor KIT (CD117), a stem cell growth factor receptor. Based on clinical and biochemical criteria, the World Health Organization (WHO) divided mastocytosis into different subclasses. The exact prevalence of mastocytosis remains elusive, but it is estimated that the disease affects approximately 1 in 10,000 persons. The clinical presentation of mastocytosis varies significantly, ranging from asymptomatic patients to a life-threatening disease with multiple organ involvement, potentially leading to cytopenia, malabsorption, hepatosplenomegaly, lymphadenopathy, ascites or osteolytic bone lesions with pathological fractures. Patients with mastocytosis may experience symptoms related to release of MC mediators, such as flushing or diarrhea or even more severe symptoms such as anaphylaxis. Recently, a new genetic trait, hereditary alpha tryptasemia (HaT), was described which involves a copy number variation in the TPSAB1-gene. Its role as standalone multisystem syndrome is heavily debated. There is emerging evidence suggesting there might be a link between HaT and due to the increased prevalence of HaT in patients with SM. The aim of this review is to provide a practical roadmap for diagnosis and management of mastocytosis and its associated entities, since there are still many misconceptions about these topics.Abbreviations: AdvSM: Advanced systemic mastocytosis; ASM: Aggressive systemic mastocytosis; aST: acute serum tryptase; BM: Bone marrow; BMM: Bone marrow mastocytosis; bST: baseline serum tryptase; CM: Cutaneous mastocytosis; DCM: Diffuse cutaneous mastocytosis; HVA: Hymenoptera venom allergy; HaT: Hereditary alpha tryptasemia; ISM: Indolent systemic mastocytosis; MC: Mast cell; MCA: Mast cell activation; MCAS: Mast cell activation syndrome; MCL: Mast cell leukemia; MIS: Mastocytosis in the skin; MMAS: Monoclonal mast cell activation syndrome; MPCM: Maculopapular cutaneous mastocytosis; SM: Systemic mastocytosis; SM-AHN: Systemic mastocytosis with associated hematological neoplasm; SSM: Smouldering systemic mastocytosis; VIT: Venom immunotherapy.

Patient-reported disease-specific quality-of-life and symptom severity in systemic mastocytosis.

BACKGROUND: Presently, no validated data exist on symptom severity and disease-specific quality-of-life (QoL) for patients with mastocytosis. Simultaneously, clinical trials and drug application processes increasingly mandate reporting patients' perspectives on symptoms and QoL. We report on the development and validation of the mastocytosis quality-of-life questionnaire (MQLQ) and the mastocytosis symptom assessment form (MSAF). METHODS: Both outcome measures were developed in a standardized stepwise method, starting with the identification of items in focus groups (n = 12), item reduction and subsequent cross-sectional validation in a 63% female cohort of 164 adult patients with indolent systemic mastocytosis. RESULTS: The MSAF reveals that fatigue is the severest mastocytosis symptom while the MQLQ indicates that fear of anaphylaxis mostly impacts QoL. Cross-sectional validity was assessed by correlating both individual domains and the total scores of the MQLQ and MSAF with independent measures of mastocytosis. The total scores of both the MQLQ (P < 0.001; Spearman's r: 0.568) and the MSAF (P < 0.001; Spearman's r: 0.559) correlated significantly with the consensus on physician-scored mediator symptoms. The MQLQ domains displayed a high internal consistency (Cronbach's alpha: 0.841-0.958) and the domains 'bones', 'skin symptoms' and 'anaphylaxis' differed significantly between patients with and without osteoporosis, urticaria pigmentosa or anaphylaxis, respectively (P < 0.001). CONCLUSIONS: The MQLQ is the first disease-specific QoL questionnaire for mastocytosis and is complemented by the MSAF, a short and convenient symptom scoring form. Both patient-reported outcome measures are valid, reliable and discriminate between patients with different disease characteristics, making them useful instruments for clinical research.

Proposed diagnostic algorithm for patients with suspected mastocytosis: a proposal of the European Competence Network on Mastocytosis.

Mastocytosis is an emerging differential diagnosis in patients with more or less specific mediator-related symptoms. In some of these patients, typical skin lesions are found and the diagnosis of mastocytosis can be established. In other cases, however, skin lesions are absent, which represents a diagnostic challenge. In the light of this unmet need, we developed a diagnostic algorithm for patients with suspected mastocytosis. In adult patients with typical lesions of mastocytosis in the skin, a bone marrow (BM) biopsy should be considered, regardless of the basal serum tryptase concentration. In adults without skin lesions who suffer from mediator-related or other typical symptoms, the basal tryptase level is an important parameter. In those with a slightly increased tryptase level, additional investigations, including a sensitive KIT mutation analysis of blood leucocytes or measurement of urinary histamine metabolites, may be helpful. In adult patients in whom (i) KIT D816V is detected and/or (ii) the basal serum tryptase level is clearly increased (>25-30 ng/ml) and/or (iii) other clinical or laboratory features suggest the presence of 'occult' mastocytosis or another haematologic neoplasm, a BM investigation is recommended. In the absence of KIT D816V and other signs or symptoms of mastocytosis or another haematopoietic disease, no BM investigation is required, but the clinical course and tryptase levels are monitored in the follow-up. In paediatric patients, a BM investigation is usually not required, even if the tryptase level is increased. Although validation is required, it can be expected that the algorithm proposed herein will facilitate the management of patients with suspected mastocytosis and help avoid unnecessary referrals and investigations.

Tryptase and histamine metabolites as diagnostic indicators of indolent systemic mastocytosis without skin lesions.

BACKGROUND: Risk indicators of indolent systemic mastocytosis (ISM) in adults with clinical suspicion of ISM without accompanying skin lesions [urticaria pigmentosa (UP)] are lacking. This study aimed at creating a decision tree using clinical characteristics, serum tryptase, and the urinary histamine metabolites methylimidazole acetic acid (MIMA) and methylhistamine (MH) to select patients for bone marrow investigations to diagnose ISM. METHODS: Retrospective data analysis of all adults, in whom bone marrow investigations were performed to diagnose ISM, was carried out. RESULTS: In total, 142 patients were included. SM was absent in all 44 patients with tryptase <10 µg/l, in 45 of 98 (46%) patients with tryptase ≥10 µg/l and in 18 of 52 patients (35%) with tryptase >20 µg/l. Above 43 µg/l, all patients had ISM (n = 11). Male gender, insect venom anaphylaxis as presenting symptom, tryptase, MIMA, and MH were independent ISM predictors. If tryptase was ≥10 µg/l, the diagnostic accuracy of MIMA and MH was high (areas under the ROC curve 0.92). CONCLUSIONS: In suspected patients without UP, the ISM risk is very low (if present at all) if tryptase is <10 µg/l. If tryptase is ≥10 µg/l, this risk depends on MIMA and MH, being low if these are normal, but high if these are elevated. Male gender and insect venom anaphylaxis are additional risk indicators. We recommend refraining from bone marrow examinations in suspected patients without UP if tryptase is <10 µg/l. Our results question the reliability of the minor diagnostic World Health Organization criterion of tryptase >20 µg/l.

Flow cytometric analysis of cytokine expression in short-term allergen-stimulated T cells mirrors the phenotype of proliferating T cells in long-term cultures.

BACKGROUND: Allergen-specific T(H) cells play an important role in IgE-mediated disorders as allergies. Since this T(H) cell-population only accounts for a small percentage of T(H) cells, they are difficult to phenotype without prior selection or expansion. METHODS: Grass-pollen-specific T(H) cell profiles were evaluated in 5 allergic and 4 non-allergic individuals using three different approaches: CD154 expression on ex vivo grass-pollen-activated PBMCs (i); CFSE-dilution in grass-pollen-restimulated PBMCs (ii) and T cell lines enriched for allergen-specific T cells (iii). RESULTS: Relatively low numbers of allergen-specific T(H) cells were detected using CD154 expression, limiting the power to detect phenotypic differences between allergic and non-allergic individuals. In contrast, higher frequencies of proliferating T(H) cells were detected by loss-of-CFSE intensity in PBMCs and TCLs after grass-pollen-stimulation, resulting in the detection of significantly more IL-4 producing T(H) cells in allergic vs non-allergic individuals. In addition, higher numbers of IFNγ producing T(H) cells were detected in long-term cultures compared to the CD154 expressing T(H) cells. CONCLUSION: To detect allergen-specific T(H) cells for a common allergen as grass-pollen, expansion is not absolutely necessary, although within 8-day grass-pollen cultures, higher numbers of proliferating T(H) cells resulted in increased statistical power to detect phenotypic differences. However, this approach also detects more bystander activated T(H) cells. TCLs resulted in comparable percentages of cytokine expressing T cells as 8-day cultures. Therefore enrichment can be necessary for detection of T(H) cells specific for a single allergen or allergen-derived peptides, but is dispensable for the detection and phenotyping of allergen-specific T(H) cells using crude extracts.

[Desensitisation to circumvent hypersensitivity reactions; treatment with docetaxel still possible]. / Desensitisatie om overgevoeligheid te omzeilen. Behandeling met docetaxel toch mogelijk gemaakt.

A 57-year-old woman with advanced non-small cell lung carcinoma developed hypersensitivity reactions to docetaxel. Measures taken to attempt the re-administration of docetaxel failed. For the differential diagnosis, an IgE specific to docetaxel (in terms of cross-reactivity with Taxus baccata), the solubilizing agent polysorbate 80, as well as the possibility of the reaction being non-IgE-mediated, were all considered. The latter was thought to be most likely. Desensitisation has been reported to be safe and effective in protecting patients from severe hypersensitivity reactions in both IgE- and non-IgE-mediated reactions. Desensitisation in this context means the induction of temporary clinical unresponsiveness to the culprit drug. The gradual reintroduction of small doses of the drug at fixed time intervals eventually allows delivery of full therapeutic doses. Desensitisation to docetaxel was successfully carried out in a supervised setting a total of three times in this patient.

Gene expression profile, pathways, and transcriptional system regulation in indolent systemic mastocytosis.

BACKGROUND: Mastocytosis is an uncommon disease resulting from proliferation of abnormal mast cells infiltrating skin, bone marrow, liver, and other tissues. The aim of this study was to find differences in gene expression in peripheral blood cells of patients with indolent systemic mastocytosis compared to healthy controls. The second aim was to define a specific gene expression profile in patients with mastocytosis. METHODS: Twenty-two patients with indolent systemic mastocytosis and 43 healthy controls were studied. Whole genome gene expression analysis was performed on RNA samples isolated from the peripheral blood. For amplification and labelling of the RNA, the Illumina TotalPrep 96 RNA Amplification Kit was used. Human HT-12_V3_expression arrays were processed. Data analysis was performed using GeneSpring, Genecodis, and Transcriptional System Regulators. RESULTS: Comparison of gene expression between patients and controls revealed a significant difference (P < 0.05 corrected for multiple testing) and the fold change difference >2 in gene expression in 2303 of the 48.794 analysed transcripts. Functional annotation indicated that the main pathways in which the differently expressed genes were involved are ubiquitin-mediated proteolysis, MAPK signalling pathway, pathways in cancer, and Jak-STAT signalling. The expression distributions for both groups did not overlap at all, indicating that many genes are highly differentially expressed in both groups. CONCLUSION: We were able to find abnormalities in gene expression in peripheral blood cells of patients with indolent systemic mastocytosis and to construct a gene expression profile which may be useful in clinical practice to predict the presence of mastocytosis and in further research of novel drugs.

Mastocytosis and insect venom allergy: diagnosis, safety and efficacy of venom immunotherapy.

The most important causative factor for anaphylaxis in mastocytosis are insect stings. The purpose of this review is to analyse the available data concerning prevalence, diagnosis, safety and effectiveness of venom immunotherapy (VIT) in mastocytosis patients. If data were unclear, authors were contacted personally for further information. Quality of evidence (A: high, B: moderate, C: low and D: very low) and strength of recommendation (strong 1 and weak 2) concerning VIT in mastocytosis patients are assessed according to the Grading of Recommendations Assessment, Development and Evaluation and are marked in square brackets. Results of VIT were described in 117 patients to date. The mean rate of side-effects during treatment in studies published so far is 23.9% (7.6% requiring adrenaline) with an overall protection rate of 72%. Based on the review we conclude that (1) mastocytosis patients have a high risk of severe sting reactions in particular to yellow jacket, (2) VIT could be suggested [2] in mastocytosis, (3) probably should be done life long [2], (4) VIT in mastocytosis is accompanied by a higher frequency of side-effects, so (5) special precautions should be taken into account notably during the built up phase of the therapy [2], (6) VIT is able to reduce systemic reactions, but to a lesser extent compared to the general insect venom allergic population [2], so (7) patients should be warned that the efficacy of VIT might be less than optimal and they should continue carrying two adrenaline auto injectors [2].

Diagnosis of Hymenoptera venom allergy.

The purpose of diagnostic procedure is to classify a sting reaction by history, identify the underlying pathogenetic mechanism, and identify the offending insect. Diagnosis of Hymenoptera venom allergy thus forms the basis for the treatment. In the central and northern Europe vespid (mainly Vespula spp.) and honeybee stings are the most prevalent, whereas in the Mediterranean area stings from Polistes and Vespula are more frequent than honeybee stings; bumblebee stings are rare throughout Europe and more of an occupational hazard. Several major allergens, usually glycoproteins with a molecular weight of 10-50 kDa, have been identified in venoms of bees, vespids. and ants. The sequences and structures of the majority of venom allergens have been determined and several have been expressed in recombinant form. A particular problem in the field of cross-reactivity are specific immunoglobulin E (IgE) antibodies directed against carbohydrate epitopes, which may induce multiple positive test results (skin test, in vitro tests) of still unknown clinical significance. Venom hypersensitivity may be mediated by immunologic mechanisms (IgE-mediated or non-IgE-mediated venom allergy) but also by nonimmunologic mechanisms. Reactions to Hymenoptera stings are classified into normal local reactions, large local reactions, systemic toxic reactions, systemic anaphylactic reactions, and unusual reactions. For most venom-allergic patients an anaphylactic reaction after a sting is very traumatic event, resulting in an altered health-related quality of life. Risk factors influencing the outcome of an anaphylactic reaction include the time interval between stings, the number of stings, the severity of the preceding reaction, age, cardiovascular diseases and drug intake, insect type, elevated serum tryptase, and mastocytosis. Diagnostic tests should be carried out in all patients with a history of a systemic sting reaction to detect sensitization. They are not recommended in subjects with a history of large local reaction or no history of a systemic reaction. Testing comprises skin tests with Hymenoptera venoms and analysis of the serum for Hymenoptera venom-specific IgE. Stepwise skin testing with incremental venom concentrations is recommended. If diagnostic tests are negative they should be repeated several weeks later. Serum tryptase should be analyzed in patients with a history of a severe sting reaction.

Mastocytosis and adverse reactions to biogenic amines and histamine-releasing foods: what is the evidence?

BACKGROUND: It has been suggested that normal concentrations of biogenic amines and 'histamine-releasing foods' may exacerbate symptoms in mastocytosis. The purpose of this study was to look for scientific evidence in the literature on diets restricted in biogenic amines and histamine-releasing foods in the treatment of mastocytosis. METHODS: Medline (1966 to 2004), Cinahl (1982 to 2004) and the Cochraine Library were searched for double-blind placebo-controlled food challenge (DBPCFC) studies with biogenic amines and/or histamine-releasing foods in mastocytosis. RESULTS: No studies employing DBPCFC with dietary biogenic amines or histamine-releasing foods in mastocytosis were found. Only a few in vitro studies in other diseases, animal studies and studies in humans in which histamine-releasing agents were incubated directly with duodenal tissues were found. One case was reported of severe adverse reactions to alcohol in mastocytosis, objectified by an open challenge. CONCLUSION: Despite the widespread belief that biogenic amines and histamine-releasing foods may cause allergy-like, non-IgE-mediated symptoms in certain patients, the role of diets restricted in biogenic amines and histamine-releasing foods in the treatment of mastosytosis remains hypothetical but worthy of further investigation. There is some evidence for adverse reactions to alcohol in mastocytosis.