Efficacy and Safety of Iron Chelation Therapy After Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Thalassemia Patients: A Retrospective Observational Study.

BACKGROUND: Studies on the increased body iron load in patients with thalassemia major have thoroughly demonstrated the problems caused by iron overload. In patients who undergo hematopoietic stem cell transplantation (HSCT) as curative therapy, iron overload continues long after transplantation. There are few pediatric studies on chelation therapy in the posttransplant period. In this study, we present the outcomes of our patients who received posttransplant oral chelation therapy. PATIENTS AND METHODS: This retrospective observational study evaluated the outcomes of pediatric patients with thalassemia major who used oral chelation therapy after allogeneic HSCT at the Akdeniz University Pediatric Bone Marrow Unit between January 2008 and October 2019. RESULTS: Deferasirox therapy was initiated in 58 pediatric patients who underwent HSCT for thalassemia. Pretreatment mean serum ferritin was 2166±1038 ng/mL. Treatment was initiated at a mean of 12±6.7 months after transplantation and continued for a mean of 15.7±11.5 months. At treatment discontinuation, the mean serum ferritin was 693±405 ng/mL and the mean reduction was -1472.75±1121.09 ng/mL (P<0.001 vs. posttreatment). Serum ferritin was below 500 ng/mL in 52% of the patients at treatment discontinuation. Manageable side effects such as nausea, vomiting, liver enzyme elevation, and proteinuria were observed in 17% of the patients, while one patient developed ototoxicity. CONCLUSIONS: Deferasirox therapy effectively reduces iron overload in the posttransplant period. Studies evaluating the effects of early treatment on the graft may help to establish guidelines for posttransplant chelation therapy. Clear guidelines are needed regarding when to initiate and discontinue treatment.

Assessment of in vivo mast cell reactivity in patients with systemic mastocytosis.

BACKGROUND: Patients with systemic mastocytosis (SM) have clinical signs of mast cell (MC) activation and increased levels of MC mediators. It is unclear whether the increased mediator levels are caused by increased numbers of tissue MCs, or whether these cells in affected individuals have a hyperactive phenotype. OBJECTIVE: To determine reactivity of the skin and the airways to directly acting mediators and indirectly acting mast cell secretagogues in subjects with SM. METHODS: Skin reactivity to morphine and histamine, and airway responsiveness to mannitol and methacholine, was assessed in 15 patients with SM, 11 patients with allergic asthma (A) and 13 healthy controls (HC). Serum tryptase and urinary metabolites of the MC mediators histamine and prostaglandin D2 were measured, as well as ex vivo basophil histamine release. RESULTS: Mast cell mediators in the blood and urine were significantly higher in patients with SM than in HC and A controls. Responsiveness to local activation of skin MCs (by morphine) and airway MCs (by mannitol) was similar in SM and HC groups. Likewise, end-organ responsiveness in the skin to histamine, and in the airways to methacholine, was similar in all three subject groups. There was no evidence of increased basophil reactivity in SM patients. CONCLUSIONS AND CLINICAL RELEVANCE: Mast cells in the skin and airways of subjects with SM do not exhibit hyper-reactivity towards the MC-activating stimuli morphine and mannitol, respectively. Therefore, the highly elevated baseline levels of MC mediators in SM are most likely due to increased MC numbers, rather than altered MC responsiveness. The underlying mechanisms could involve leakage of MC mediators, or dysfunctions in mediator synthesis, storage and release. One clinical implication of our study is that there is no contraindication to perform skin tests using morphine in subjects with mastocytosis.

Mastocytosis: the puzzling clinical spectrum and challenging diagnostic aspects of an enigmatic disease.

Mastocytosis is a complex disorder characterized by the accumulation of abnormal mast cells (MC) in the skin, bone marrow and/or other visceral organs. The clinical manifestations result from MC-derived mediators and, less frequently, from destructive infiltration of MCs. Patients suffer from a variety of symptoms including pruritus, flushing and life-threatening anaphylaxis. Whilst mastocytosis is likely to be suspected in a patient with typical skin lesions [i.e. urticaria pigmentosa (UP)], the absence of cutaneous signs does not rule out the diagnosis of this disease. Mastocytosis should be suspected in cases of recurrent, unexplained or severe insect-induced anaphylaxis or symptoms of MC degranulation without true allergy. In rare cases, unexplained osteoporosis or unexplained haematological abnormalities can be underlying feature of mastocytosis, particularly when these conditions are associated with elevated baseline serum tryptase levels. The diagnosis is based on the World Health Organization criteria, in which the tryptase level, histopathological and immunophenotypic evaluation of MCs and molecular analysis are crucial. A somatic KIT mutation, the most common of which is D816V, is usually detectable in MCs and their progenitors. Once a diagnosis of systemic mastocytosis (SM) is made, it is mandatory to assess the burden of the disease, its activity, subtype and prognosis, and the appropriate therapy. Mastocytosis comprises seven different categories that range from indolent forms, such as cutaneous and indolent SM, to progressive forms, such as aggressive SM and MC leukaemia. Although prognosis is good in patients with indolent forms of the disease, patients with advanced categories have a poor prognosis.

High prevalence of anaphylaxis in patients with systemic mastocytosis - a single-centre experience.

BACKGROUND: Systemic mastocytosis (SM) is a clonal mast cells disorder characterized by the proliferation, accumulation and activation of mast cells in extracutaneous tissues. The clinical picture is heterogeneous and may range from asymptomatic to potentially fatal anaphylactic reactions due to excessive mast cell mediator release. OBJECTIVE: The aim of this study was to investigate the prevalence and trigger factors of anaphylactic reactions among adult SM patients. We also explored the clinical spectrum of mast cell mediator-related symptoms in patients with SM. METHODS: This descriptive study was performed among 84 consecutive adult (≥ 18 years) patients those were diagnosed with SM according to WHO criteria. Sixty-six of the patients also underwent a comprehensive allergy work-up. RESULTS: Sixty of 84 patients with SM (71%) had bone marrow mast cell aggregates and fulfilled the major criteria for SM and 76 patients (91%) had indolent disease. Simultaneous occurrence of cutaneous mastocytosis was observed in 59 patients (70%). Thirty-six patients (43%) had had at least one episode of an anaphylactic reaction. The clinical courses of the reactions were usually severe and patients often presented with syncope attacks (72%). Most patients reacted after hymenoptera venom stings (19/36; 53%). In 39% (14/36), a clear aetiology could not be determined. While males and females were equally frequent among the patients with SM, anaphylaxis patients showed a male predominance (61%). Anaphylactic reactions occurred more frequently in patients without cutaneous engagement. The rate of allergy sensitization was significantly higher in SM patients with anaphylaxis as compared with non-anaphylaxis SM patients, 70% vs. 23%, respectively (P = 0.0002). CONCLUSIONS AND CLINICAL RELEVANCE: Anaphylaxis is more prevalent in patients with SM, predominantly in patients with atopic SM. Hymenoptera venom-induced and idiopathic anaphylaxis were the most frequent elicitors. Our findings implicate that all mastocytosis patients with anaphylaxis should undergo detailed allergological assessment before considering treatment and preventive measures.

The presence of mast cell clonality in patients with unexplained anaphylaxis.

BACKGROUND: The mechanisms by which mast cells in patients with unexplained anaphylaxis (UEA) are triggered remain elusive. Onset of episodes is unpredictable and often recurrent. The substantial overlap between the clinical manifestations of UEA and clonal mast cell disorders (CMD) suggests an association between these rare disorders. The two forms of CMD characterized to date are systemic mastocytosis (SM) and monoclonal mast cell activation syndrome (MMAS). OBJECTIVE: To examine the hypothesis that the pathogenesis of UEA reflects the presence of aberrant subpopulations of mast cells. METHODS: Thirty (14 men, 16 women) patients (≥ 18 years) suffering from UEA and with no signs of cutaneous mastocytosis were recruited. Patients underwent an initial complete allergy work-up to confirm the diagnosis of UEA. Level of baseline serum tryptase (sBT) and total IgE were determined. In addition, a bone marrow examination was performed on all 30 patients to investigate possible underlying CMD. RESULTS: Fourteen (47%) of our cases (nine men, five women) were diagnosed with CMD: 10 with SM and four with MMAS. Four of the 10 patients with SM had mast cell aggregates in their bone marrow. All patients with SM exhibited a sBT level > 11.4 ng/mL, whereas this level was elevated in only two of those with MMAS and four with UAE but not diagnosed with CMD. Total IgE levels were lower in the group of patients with CMD (P < 0.03). CONCLUSION AND CLINICAL RELEVANCE: The pathogenic mechanism underlying UEA could be explained by the presence of immunophenotypically aberrant mast cells with clonal markers in 47% of our subjects, indicating that clonal mast cell disorders are present in a substantial subset of these patients. Thus, the presence of CMD should be considered in patients with UEA if they have an elevated level of sBT (≥ 11.4 ng/mL) and cardiovascular symptoms such as syncope.

Analysis of V600E BRAF and D816V KIT mutations in systemic mastocytosis.

Most patients with systemic mastocytosis (SM) carry a D816 V KIT mutation causing a ligand-independent activation of the receptor. Down-stream of KIT is several components known to be mutated in different malignancies. RAF is among the most frequently mutated kinases, where BRAF V600E mutation occurs in most hairy cell leukemias (HCL) and half of malignant melanomas. We investigated BRAF mutations in 36 subjects with different forms of SM, but could not detect BRAF mutation in any of the cases, not even in the mast cell lineage of a patient with V600E BRAF-positive HCL. Thus, although BRAF is commonly mutated it appears not to be present in SM.

Systemic mastocytosis: progressive evolution of an occult disease into fatal mast cell leukemia: unique findings on an unusual hematological neoplasm.

Systemic mastocytosis (SM) may be associated with a clonal hematopoietic non-mast cell-lineage disease (AHNMD). SM and AHNMD even may be clonally related. This report contributes to a better understanding of the different morphological aspects of SM by demonstrating that various AHNMDs can be detected in one patient during the course of disease. Routinely processed biopsy specimens of bone marrow and spleen removed from a 63-year-old man were investigated including a broad panel of immunohistochemical stainings. KIT codon 816 mutation analysis was carried out by melting point analysis of nested PCR products amplified from DNA of pooled microdissected mast cells. The histomorphological features of the initial bone marrow showed diffuse infiltration by hairy cell leukemia (HCL). Occult SM was only detected retrospectively by demonstration of a slight diffuse increase in loosely scattered, spindle-shaped mast cells carrying the activating point mutation KIT ( D816V ). In the second bone marrow, core biopsy removed about two years later HCL had been completely eradicated, while a diagnosis of SM-AHNMD with multifocal compact mast cell infiltrates associated with a myeloproliferative neoplasm (MPN) and significant increase in eosinophilic granulocytes was established. The third and last bone marrow biopsy specimen lacked the features of both MPN and HCL but showed progression into a secondary mast cell leukemia (MCL) with a focal sarcomatous component. To the best of the authors' knowledge, this is the first description of a case of SM-AHNMD with coexisting hematological neoplasms of lymphatic and myeloid origin initially presenting as occult disease and terminating as secondary MCL.

FcgammaRIIIB polymorphism: evidence that NA1/NA2 and SH are located in two closely linked loci and that the SH allele is linked to the NA1 allele in the Danish population.

BACKGROUND: The neutrophil-specific antigens NA1, NA2, and SH are well-recognized allotypic forms of FcgammaRIIIB. Individuals carrying all three FcgammaRIIIB genes were recently described. STUDY DESIGN AND METHODS: A Danish population (n = 200) was typed for NA1, NA2, and SH by polymerase chain reaction with sequence-specific primers (PCR-SSP). Twelve individuals with three FcgammaRIIIB genes were further genotyped by PCR-based restriction fragment length polymorphism and by DNA sequencing. Family studies were performed on three individuals who carry three FcgammaRIIIB genes. RESULTS: The gene frequencies for NA1, NA2, and SH were 0.365, 0.635, and 0.030, respectively. In eight individuals (4%), all three FcgammaRIIIB genes were identified. All 12 SH+ individuals were NA1+. CONCLUSION: The NA1, NA2, and SH gene frequencies observed in Danes are similar to those in other white populations. The distribution of FcgammaFIIIB genotypes in the Danish population strongly indicates that the NA and the SH systems are located in two closely linked loci and that SH is closely linked to NA1. Finally, a new PCR-SSP was developed to distinguish NA2 from SH.