ELN Foundation and France National Cancer Institute.

No abstract

The vast majority of patients with systemic mastocytosis (SM) carry the somatic D816V mutation in the KIT gene. The KIT D816V mutation is one of the minor criteria for a diagnosis of SM according to the 2008 World Health Organization classification of myeloproliferative neoplasms. In the present study, we present a real-time qPCR assay that allows quantification of as little as 0.003% KIT D816V mutation-positive cells. A total of 61 samples from 31 cases of SM were included in the study. We detected the mutation in skin or bone marrow in 95% of the cases of SM. We demonstrate the clinical relevance of the assay by identifying as little as 0.03% mutation-positive cells in bone marrow aspirates from SM patients and calculate the analytical sensitivity of negative samples to determine the reliability of the result. We further demonstrate that this method also detects the KIT D816V mutation in peripheral blood in 81% of the mutation-positive cases with SM. The method also allows comparison of mutation-positive and mast cell fractions to determine whether the mutation is present in non-mast cells, a parameter that has recently been reported to be of prognostic importance in patients with indolent SM. Finally, the assay is suitable for use in prospective studies of the KIT D816V allele burden as a treatment endpoint in SM.

SummaryMastocytosis is a heterogeneous group of diseases characterized by abnormal proliferation of mast cells. Systemic mastocytosis (SM), in which abnormal mast cells are present in tissues beyond the skin, is divided into seven subcategories with varying degrees of severity and prognosis. Very little is known about the epidemiology of SM and its subcategories. This retrospective cohort study of 548 adults with SM diagnosed 1997-2010 was constructed using linked Danish national health registries. The most common subtype of mastocytosis was indolent SM (including urticaria pigmentosa) (n = 450; 82%), followed by SM with subtype unknown (n = 61; 11%), SM with associated clonal haematological non-mast cell lineage disease (n = 24; 4%), aggressive SM (n = 8; 2%), and mast cell leukaemia (n = 5; 1%). The incidence rate for SM (all subtypes including urticaria pigmentosa) was 0Á89 per 100 000 per year. Cumulative incidence was 12Á46 per 100 000, and the 14-year limited-duration prevalence as of 1 January, 2011 was 9Á59 per 100 000. This nationwide cohort from Denmark is the first population-based epidemiological study of mastocytosis. In this cohort of patients aged 15 years and older, SM was found to be overall relatively rare with notable variation by subtype for patient characteristics, survival and epidemiological measures.

The recent progress in sensitive KIT D816V mutation analysis suggests that mutation analysis of peripheral blood (PB) represents a promising diagnostic test in mastocytosis. However, there is a need for systematic assessment of the analytical sensitivity and specificity of the approach in order to establish its value in clinical use. We therefore evaluated sensitive KIT D816V mutation analysis of PB as a diagnostic test in an entire case-series of adults with mastocytosis. We demonstrate for the first time that by using a sufficiently sensitive KIT D816V mutation analysis, it is possible to detect the mutation in PB in nearly all adult mastocytosis patients. The mutation was detected in PB in 78 of 83 systemic mastocytosis (94%) and 3 of 4 cutaneous mastocytosis patients (75%). The test was 100% specific as determined by analysis of clinically relevant control patients who all tested negative. Mutation analysis of PB was significantly more sensitive than serum tryptase >20 ng/mL. Of 27 patients with low tryptase, 26 tested mutation positive (96%). The test is furthermore readily available and we consider the results to serve as a foundation of experimental evidence to support the inclusion of the test in diagnostic algorithms and clinical practice in mastocytosis.

SummaryThe impact of first-line treatment with the anti-CD 20 chimeric monoclonal antibody rituximab in patients with warm-antibody reactive autoimmune haemolytic anaemia (WAIHA) is unknown. We report the first randomized study of 64 patients with newly diagnosed WAIHA who received prednisolone and rituximab combined (N = 32) or prednisolone monotherapy (N = 32). After 12 months, a satisfactory response was observed in 75% of the patients treated with rituximab and prednisolone but in a significantly smaller proportion (36%) of those given prednisolone alone (P = 0Á003). Furthermore, relapse-free survival was significantly better after the combined therapy than after prednisolone monotherapy (P = 0Á02). After 36 months, about 70% of the patients were still in remission in the rituximab-prednisolone group, whereas only about 45% were still in complete or partial remission in the prednisolone group. There was no significant difference between the two groups regarding adverse reactions to the studied medications. Likewise, serious adverse events were equally distributed, and no allergic reactions to rituximab were recorded. In conclusion, our data show that using rituximab and prednisolone combined rather than prednisolone alone as first-line treatment in WAIHA increases both the rate and the duration of the response.

Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by accumulation of a periodic acid Schiff (PAS)-positive eosinophilic material in the distal airways. For decades, the standard treatment of PAP has been whole lung lavage (WLL), where large quantities of saline are instilled into the lungs to remove the proteinaceous material. However, not all patients respond to this treatment. Thus, new treatment modalities, such as subcutaneous or inhaled granulocyte macrophage colony-stimulating factor (GM-CSF), and the CD20 antibody rituximab and plasmapheresis, have been investigated. Based on the current literature, a stepwise treatment plan is suggested starting with WLL, continuing to inhaled GM-CSF, and then to rituximab if the former treatment regimes are unsuccessful.

Omalizumab appears to be a promising treatment option in SM, effectively preventing anaphylaxis and improving chronic MC mediator-related symptoms, insufficiently controlled by conventional therapy. Controlled studies are needed to substantiate findings.