Diagnosis and management of acquired aplastic anemia in childhood. Guidelines from the Marrow Failure Study Group of the Pediatric Haemato-Oncology Italian Association (AIEOP).

Acquired aplastic anemia (AA) is a rare heterogeneous disorder characterized by pancytopenia and hypoplastic bone marrow. The incidence is 2-3 per million population per year in the Western world, but 3 times higher in East Asia. Survival in severe aplastic anemia (SAA) has improved significantly due to advances in hematopoietic stem cell transplantation (HSCT), immunosuppressive therapy, biologic agents, and supportive care. In SAA, HSCT from a matched sibling donor (MSD) is the first-line treatment. If a MSD is not available, options include immunosuppressive therapy (IST), matched unrelated donor, or haploidentical HSCT. The purpose of this guideline is to provide health care professionals with clear guidance on the diagnosis and management of pediatric patients with AA. A preliminary evidence-based document prepared by a group of pediatric hematologists of the Bone Marrow Failure Study Group of the Italian Association of Pediatric Hemato-Oncology (AIEOP) was discussed, modified and approved during a series of consensus conferences that started online during COVID 19 and continued in the following years, according to procedures previously validated by the AIEOP Board of Directors.

A mutation in caspase-9 decreases the expression of BAFFR and ICOS in patients with immunodeficiency and lymphoproliferation.

Lymphocyte apoptosis is mainly induced by either death receptor-dependent activation of caspase-8 or mitochondria-dependent activation of caspase-9. Mutations in caspase-8 lead to autoimmunity/lymphoproliferation and immunodeficiency. This work describes a heterozygous H237P mutation in caspase-9 that can lead to similar disorders. H237P mutation was detected in two patients: Pt1 with autoimmunity/lymphoproliferation, severe hypogammaglobulinemia and Pt2 with mild hypogammaglobulinemia and Burkitt lymphoma. Their lymphocytes displayed defective caspase-9 activity and decreased apoptotic and activation responses. Transfection experiments showed that mutant caspase-9 display defective enzyme and proapoptotic activities and a dominant-negative effect on wild-type caspase-9. Ex vivo analysis of the patients' lymphocytes and in vitro transfection experiments showed that the expression of mutant caspase-9 correlated with a downregulation of BAFFR (B-cell-activating factor belonging to the TNF family (BAFF) receptor) in B cells and ICOS (inducible T-cell costimulator) in T cells. Both patients carried a second inherited heterozygous mutation missing in the relatives carrying H237P: Pt1 in the transmembrane activator and CAML interactor (TACI) gene (S144X) and Pt2 in the perforin (PRF1) gene (N252S). Both mutations have been previously associated with immunodeficiencies in homozygosis or compound heterozygosis. Taken together, these data suggest that caspase-9 mutations may predispose to immunodeficiency by cooperating with other genetic factors, possibly by downregulating the expression of BAFFR and ICOS.

X-linked thrombocytopenia and Wiskott-Aldrich syndrome are allelic diseases with mutations in the WASP gene.

X-linked thrombocytopenia (XLT) is a rare recessive hereditary disorder characterized by isolated thrombocytopenia with small-sized platelets. The XLT locus has been located to chromosome Xp11 by linkage analysis, which is also where the recently cloned Wiskott-Aldrich syndrome (WAS) gene, maps. The relationship between XLT and WAS has long been debated; they might be due to different mutations of the same gene or to mutations in different genes. We now show that mutations in the WAS gene, different from those found in WAS patients, are present in three unrelated male patients with isolated thrombocytopenia and small-sized platelets. Our results demonstrate that XLT and WAS are allelic forms of the same disease, but the causes of the differences need to be further investigated.

Familial tumoral calcinosis and testicular microlithiasis associated with a new mutation of GALNT3 in a white family.

BACKGROUND: Familial tumoral calcinosis (FTC) is a rare autosomal recessive disease characterised by the development of multiple calcified masses in periarticular soft tissues; GALNT3 gene mutations have recently been described in an African American and in a Druse Arab family with FTC. OBJECTIVE: To report the clinical and histological features caused by a new GALNT3 mutation in a white family. RESULTS: Homozygosity for the nonsense mutation Lys463X was found in both affected siblings, who displayed a classic phenotype, the male also having testicular microlithiasis. He is the first subject described with testicular microlithiasis in FTC. CONCLUSIONS: The high testicular expression of GALNT3 suggests that the gene alteration could act locally by causing deposition of calcium, and the testis may be an underestimated site of calcification in FTC. Autoimmune diseases are present in several members of the family. Although immune disorders have been described in FTC, autoimmunity does not segregate with the GALNT3 mutation in this family.

Defective function of Fas in patients with type 1 diabetes associated with other autoimmune diseases.

Fas (CD95) triggers programmed cell death and is involved in cell-mediated cytotoxicity and in shutting off the immune response. Inherited loss-of-function mutations hitting the Fas system cause the autoimmune/lymphoproliferative syndrome (ALPS). We have recently shown that ALPS patients' families display increased frequency of common autoimmune diseases, including type 1 diabetes. This work evaluates Fas function in type 1 diabetic patients without typical ALPS. Cell death induced by anti-Fas monoclonal antibody was investigated in T-cells from 13 patients with type 1 diabetes alone and 19 patients with type 1 diabetes plus other autoimmune diseases (IDDM-P). Moreover, we analyzed 19 patients with thyroiditis alone (TYR), because most IDDM-P patients displayed thyroiditis. Frequency of resistance to Fas-induced cell death was significantly higher in patients with IDDM-P (73%) than in type 1 diabetic (23%) or TYR (16%) patients or in normal control subjects (3%). The defect was specific because resistance to methyl-prednisolone-induced cell death was not significantly increased in any group. Fas was always expressed at normal levels, and no Fas mutations were detected in four Fas-resistant IDDM-P patients. Analysis of the families of two Fas-resistant patients showing that several members were Fas-resistant suggests that the defect has a genetic component. Moreover, somatic fusion of T-cells from Fas-resistant subjects and the Fas-sensitive HUT78 cell line generates Fas-resistant hybrid cells, which suggests that the Fas resistance is due to molecules exerting a dominant-negative effect on a normal Fas system. These data suggest that Fas defects may be a genetic factor involved in the development of polyreactive type 1 diabetes.

The polymorphisms -318C>T in the promoter and 49A>G in exon 1 of CTLA4 and the risk of aplastic anemia in a Caucasian population.

Aplastic anemia (AA) is a rare disease with a major autoimmune pathogenetic component. CTLA4 is a T-lymphocyte surface molecule involved in the maintenance of immune tolerance. Some polymorphisms associated with a reduced expression of CTLA4, and thus presumably with increased tendency to autoimmunity, have been associated with various autoimmune diseases. In this study, we evaluated the distribution of the low expression polymorphisms -318C > T and 49A > G of CTLA4 in a population of 67 patients with acquired AA and in 100 normal controls. There was no difference in the distribution of the tested polymorphism between patients and controls and, within the patient group, between those who responded to immunosuppression vs those who did not respond. This study indicates that the polymorphisms -318C > T and 49A > G of CTLA4 do not affect the risk of developing AA and do not influence the response to immunosuppression.

Diamond-Blackfan anemia: expansion of erythroid progenitors in vitro by IL-9, but exclusion of a significant pathogenetic role for the IL-9 gene and the hematopoietic gene cluster on chromosome 5q.

Diamond-Blackfan anemia (DBA) is a congenital pure red blood cell aplasia that often requires lifelong transfusional therapy. Autosomal dominant and recessive inheritance have both been reported, suggesting genetic heterogeneity, but most cases occur sporadically. The origin of impaired erythropoiesis is unknown. Several erythroid growth factors have been thought to have a role in the pathogenesis of DBA. However, there is neither molecular nor clinical evidence for the involvement of erythropoietin (EPO), its receptor, stem cell factor (SCF), or interleukin (IL)-3, even if the addition of SCF to IL-3 and EPO does significantly increase the growth of erythroid progenitors in in vitro cultures in most patients. In this work we evaluated the possible role of another early-acting erythroid growth factor, IL-9. We found that the addition of IL-9 to SCF, IL-3, and EPO further increases burst-forming unit-erythroid growth in in vitro cultures of those DBA patients who responded to SCF. To investigate the role of the IL-9 gene, we evaluated its segregation in 22 families with members who have DBA by using a polymorphic microsatellite located within its intron 4. Lod score analysis ruled out any statistically significant involvement of the IL-9 gene in the pathogenesis of DBA. Moreover, linkage analysis with 11 highly polymorphic markers spanning 5q31.1-q33.2 excluded this region, which is included in the major cluster of genes active in hematopoiesis of the human genome.

Stem cell factor suppresses apoptosis in neuroblastoma cell lines.

Stem cell factor (SCF) is a glycoprotein growth factor produced by marrow stromal cells that acts after binding to its specific surface receptor, which is the protein encoded by the protooncogene c-kit. SCF synergizes with specific lineage factors in promoting the proliferation of primitive hematopoietic progenitors, and has been administered to expand the pool of these progenitors in cancer patients treated with high-dose chemotherapy. SCF and its c-kit receptor are expressed by some tumor cells, including myeloid leukemia, breast carcinoma, small cell lung carcinoma, melanoma, gynecological tumors, and testicular germ cell tumors. Previous studies of SCF in neuroblastoma have produced conflicting conclusions. To explore the role of SCF in neuroblastoma, we studied five neuroblastoma lines (IMR-5, SK-N-SH, SK-N-BE, AF8, and SJ-N-KP) and the neuroepithelioma line CHP-100. All lines expressed mRNA for c-kit and c-kit protein at low intensity as measured by flow cytometry, and secreted SCF in medium culture as shown by ELISA. Exogenous SCF did not modify 3H thymidine uptake in the neuroblastoma and neuroepithelioma cell lines. After 6 days' culture in the presence of anti-c-kit, the number of viable neuroblastoma cells was significantly lower than the control, and terminal deoxynucleotidyl transferase assay showed a substantial increase of apoptotic cells: The percentage of positive cells was 1-3% in the control lines, whereas in the presence of anti c-kit it varied from 29% of SK-N-BE to 92% of CHP-100. After 9 days' culture in the presence of anti-c-kit, no viable cells were detectable. These data indicate that SCF is produced by some neuroblastoma cell lines via an autocrine loop to protect them from apoptosis.

Long-term bone marrow cultures in Diamond-Blackfan anemia reveal a defect of both granulomacrophage and erythroid progenitors.

The hematopoietic defect of Diamond-Blackfan anemia (DBA) results in selective failure of erythropoiesis. Thus far, it is not known whether this defect originates from an intrinsic impediment of hematopoietic progenitors to move forward along the erythroid pathway or to the impaired capacity of the bone marrow (BM) microenvironment to support proliferation and differentiation of hematopoietic cells. Reduced longevity of long-term bone marrow cultures, the most physiologic in vitro system to study the interactions of hematopoietic progenitors and hematopoietic microenvironment, is consistent with a defect of an early hematopoietic progenitor in DBA. However, stromal adherent layers from DBA patients generated in a long-term culture system, the in vitro counterpart of BM microenvironment, did not show evidence of any morphologic, phenotypic, or functional abnormality. Our major finding was an impaired capacity of enriched CD34+ BM cell fraction from DBA patients, cultured in the presence of normal BM stromal cells, to proliferate and differentiate along the erythroid pathway. A similar impairment was observed in some DBA patients along the granulomacrophage pathway. Our result points to an intrinsic defect of a hematopoietic progenitor with bilineage potential that is earlier than previously suspected as a relevant pathogenetic mechanism of the disease. The finding of impaired granulopoiesis in some DBA patients underlines the heterogeneity of this rare disorder.

The cell death-inducing ability of glycoprotein 120 from different HIV strains correlates with their ability to induce CD4 lateral association with CD95 on CD4+ T cells.

CD4 cross-linking by HIV gp120 triggers CD4+ T cell death. Several authors have suggested that this effect is mediated by CD95, but this possibility is debated by other authors. In a previous work, we found by co-capping that gp120(451) and gp120MN, but not gp120(IIIB), induce lateral association of CD4 with CD95 on the T cell surface. In this work, we used fluorescence resonance energy transfer to confirm that CD4/CD95 lateral association is induced by gp120(451), but not gp120(IIIB). Moreover, we found that gp120 ability to induce the CD4/CD95 association correlates with ability to induce cell death, since gp120(451) and gp120MN induced higher levels of cell death than did gp120(IIIB) in PHA-derived CD4+ T cell lines. CD95 involvement in gp120-induced cell death was confirmed by showing that gp120(451) and gp120MN did not induce death in CD4+ T cells derived from patients with autoimmune/lymphoproliferative disease (ALD) and decreased CD95 function. Cell death induced by gp120MN was inhibited by a recombinant CD95/IgG.Fc molecule blocking the CD95/CD95L interaction. However, inhibition was late and only partial. These data suggest that the gp120-induced CD4/CD95 association exerts a dual effect: an early effect that is independent of CD95L and may be due to direct triggering of CD95 by gp120, and a late effect that may be due to sensitization of CD95 to triggering by CD95L. In line with the former effect, cell treatment with gp120MN activated caspase 3 in the presence of Fas/IgG.Fc, which shows that cell death induced by gp120MN independently of CD95L uses the same pathway as CD95.

Human cord blood progenitors: kinetics, regulation and their use for hemopoietic reconstitution.

The high number of cord blood (CB) hematopoietic progenitors made possible CB transplantation in children with hematologic diseases. We collected and cryopreserved CB from siblings of 11 hematologic pediatric patients for possible transplant. The number of BFU-E+CFU-GEMM and CFU-GM was adequate for engraftment. However the possibility of CB transplantation in adolescents and adults is limited by the amount of CB that can be collected. We studied the possibility of expanding the pool of CB hematopoietic progenitors by preincubation of CB CD 34+ cells with several cytokines. After pre-exposition to rhIL-3, IL-1 beta, rIL-6, GM-CSF and stem cell factor (SCF) and cloning with SCF the number of hematopoietic progenitors increased 14-18 fold compared to basal values.

Specificity of antinuclear and antiphospholipid antibodies in sera of patients with autoimmune lymphoproliferative disease (ALD).

OBJECTIVE: A human lymphoproliferative syndrome characterized by a defect of the Fas-mediated apoptosis pathway in the absence of a fas gene mutation (Autoimmune Lymphoproliferative Disease) has recently been described and characterized by autoimmune phenomena. The aim of this study was to investigate the presence of antinuclear and antiphospholipid antibodies and to define their specificity in 5 pediatric patients with this syndrome. METHODS: Antinuclear antibodies were investigated by Western Blot and IIF performed under standard as well as apoptotic conditions. The fine specificity of antiphospholipid antibodies was dissected by an ELISA for anti-beta 2-glycoprotein I, anti-prothrombin, anti-annexin V and anti-protein S antibodies, and by immunostaining on thin layer chromatography plates for antiphospholipid molecule antibodies. RESULTS: This study showed that the autoantibodies found in these patients targeted a broad spectrum of nuclear antigens which undergo redistribution from the nucleus to the cytoplasm and plasma membrane during the course of the apoptotic process. This reactivity does not comprise known specificities such as anti-extractable nuclear antigens or anti-dsDNA. Antiphospholipid antibodies were also found in these sera. A further characterization of the antiphospholipid antibodies showed the presence of a heterogeneous response with antibodies directed to negatively-charged phospholipids and antibodies targeting coagulation-related proteins (beta 2-GPI, prothrombin, annexin V) which are considered relevant antigens in the antiphospholipid syndrome. CONCLUSIONS: These results suggest that lack of tolerance due to a defect of Fas-mediated apoptosis allows the survival of B and T clones involved in the antinuclear and antiphospholipid immune responses.

Diamond-Blackfan Anaemia: an overview.

Diamond Blackfan Anaemia (DBA) is a congenital disease characterised by defective erythroid progenitor maturation. It is usually diagnosed during the first year of life. The main clinical sign is profound isolated normochromic or macrocytic anaemia, with normal numbers and function of the other haemopoietic cells. Reticulocyte counts in patients with DBA are very low. Bone marrow reflects the defective erythropoiesis, showing a very low number of erythropoietic precursors and a reduction of erythroid burst-forming unit progenitor cells. The proliferation and differentiation of the other lineages are normal. More than one-third of patients have malformations, most often involving the upper limbs and head, and the urogenital or cardiovascular systems. However, the link between these malformations and defective erythropoiesis is unclear and a defect in a molecule acting on both early embryonic development and haematopoiesis has been proposed. Whereas most cases are sporadic, inheritance is observed in 10% of patients, with a dominant or, more rarely, recessive pattern. One locus on chromosome 19q13.2 encoding ribosomal protein S19 accounts for a quarter of patients with either the dominant or the sporadic form. Families not linked with this locus have also been described. The diagnosis of DBA may be difficult and differential diagnoses include Fanconi's anaemia and acquired erythroid aplasias. Erythrocyte adenosine deaminase levels are generally high in DBA patients, which may help in the diagnosis, but they are not pathognomic. Corticosteroids are the main treatment option in DBA and these agents induce erythropoiesis in over 60% of patients. Some patients achieve complete remission, which may be either corticosteroid-induced or spontaneous. The increased in vitro erythropoiesis occasionally induced by the addition of specific cytokines, namely interleukin (IL)-3 and stem cell factor (SCF), has suggested their use in vivo. However, few patients have responded to IL-3, whereas SCF administration, though interesting in theory, has not yet been attempted. Patients who do not respond to corticosteroids and those who have to discontinue treatment because of adverse events must rely on long term transfusions, and are thus exposed to all of the associated complications. Bone marrow or cord blood transplantation has been performed in some patients. The former approach is burdened with severe complications and high mortality.

Umbilical cord blood stem cell transplantation.

Human umbilical cord blood as an alternative source of hematopoietic stem cells for bone marrow reconstitution, has recently been demonstrated to yield successful HLA-matched placental blood grafts in children. It has been shown that cord blood contains sufficient progenitor cells to effect hematological reconstitution. Since then, more than 25 cord blood stem cells (CBSCs) transplants have been performed worldwide for the treatment of a variety of malignant and nonmalignant diseases. The majority of the grafts performed thus far have utilized CBSCs from HLA-identical siblings. However, much of the interest in this setting is devoted to the potential use of CBSCs for HLA-mismatched and unrelated transplants. Preliminary results suggest that allorecognition and graft-versus-host disease may be less intense in CBSCs transplants than in recipients of similarly compatible bone marrow. This review summarizes the results and potential future applications of cord blood transplantation.

[The glucose-6-phosphate dehydrogenase/6-phosphogluconate dehydrogenase ratio in the identification of glucose-6-phosphate dehydrogenase heterozygosity]. / Il rapporto G-6PD/6-PGD nella identificazione dell' eterozigosi per la G-6PD.

Deficiency in human G-6PD is a widespread X-linked disorder, which is mainly characterized by susceptibility to hemolytic anaemia after the ingestion of certain drugs or toxic substances (e.g. pyrimidine derivates contained in fava beans). G-6PD deficiency in hemizygous males in easily detectable since enzymatic activity is almost absent. In heterozygous subjects the determination of enzymatic activity on red cell lysate cannot detect a partial G-6PD deficiency. Cytochemical methods as methemoglobin reduction test or tetrazolium reduction test are more sensitive than spectrophotometric quantitative test, but are not suitable for screening purposes. We measured both G-6PD activity and 6-PGD activity in G-6PD heterozygous females and we evaluated the G-6PD/6PGD ratio. We tested this ratio also in thalassemic traits and in G-6PD heterozygotes with thalassemic trait in order to detect the interference of thalassemic pathology with the phenotypic expression of the gene for G-6PD. We found that the mean G-6PD values were statistically reduced in G-6PD heterozygous females; on the contrary the measurement of true G-6PD activity alone is not a good tool for discriminating heterozygous subjects with and without thalassemic trait. Actually 100% and 79% of values observed were in the normal range +/- 2 DS respectively. The mean G-6PD/6-PGD ratio in heterozygotes for G-6PD deficiency with and without thalassemic trait was lower than normal and the individual values of G-6PD/6-PGD ratio were in the normal range +/- 2 DS only in a few subjects (8.3% and 10.7% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Bone marrow aplasia]. / Le aplasie midollari.

Aplastic anaemia is a haematological syndrome in which pancytopenia is due to a depletion, damage of inhibition of hemopoietic stem cells. The pathogenetic factors are still unclear: damage or inhibition of hemopoietic stem cells may be direct or indirect mediated through changes in the cellular humoral environment; evidence is accumulating that in some cases these processes are of autoimmune nature. The prognostic evaluation is based on hematological parameters at diagnosis: severe aplastic anemia (SAA) is defined by the following criteria: neutrophils less than 0.5 X 10(9)/l; reticulocytes less than 0.5 X 10(9)/l and platelets less than 20 X 10(9)/l. Survival rates in children with SAA are poor; the probability of survival at 1 year from diagnosis being 10%. In this form treatment is based on supportive therapy (transfusion and prevention of infections) and on a specific therapy: immunosuppression and/or BMT. BMT is reserved to patient with an HLA identical sibling donor and may be curative in 70-80% of cases. To date the use of antilymphocytoglobulin in SAA has also given satisfactory results with a favorable response in 50-60% of cases.

[Acute non-lymphatic leukemia in children]. / Leucemie non linfatiche acute nel bambino.

40 children (23 males, 17 females) have been diagnosed have ANLL during the period from february 1970 to september 1981. According to FAB classification, 24 cases were M1,-M2, 9 M3, 3 M4, 3 M5 and 1 M6. At diagnosis, 20 patients (50%) had leukocytes less than 10.000/mmc, 6 (15%) had leukocytes greater than 50.000mmc. Hb levels was 7 g% in 16 patients (40%); 10 children had hepatosplenomegaly (25%), 7 splenomegaly (18%) and 5 lymphoadenomegaly (13%). 4 patients had cutaneous or mucous infiltrates. None had meningeal involvement at diagnosis. According to the year of diagnosis, 3 groups can be identified. In the group I (1970-73), 11 patients have been treated with not codified combination chemotherapy as ARA-C, 6-TG, DNR, CTX, Metil-GAG. In the group II (1974-76) and in the group III (1977-81), the patients (respectively 12 and 17) have been treated according to the following protocols: LAM-5 (3), TRAP (5), COAP (1), LAM 80 (2), AIL 7402 (8), AIL 7604, AIL 7801 (6). Immunotherapy has been performed in 7 cases. CNS prophylaxis (MTX i.t. +/-ARA-C +/- RT) was given in 5 patients of group II and in 6 of group III. I patients of group I (45%), 6 of group II (50%) and 13 of group III (76%) achieved CR. Median duration of remission was 5 months in the group I and in 17 in group II and III.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoimmune lymphoproliferative syndrome and non-Hodgkin lymphoma: what 18F-fluorodeoxyglucose positron emission tomography/computed tomography can do in the management of these patients? Suggestions from a case report.

A young patient with undefined autoimmune lymphoproliferative syndrome (ALPS-U) and low back pain underwent a CT and MRI study that showed enhancing vertebral lesions, some pulmonary nodules and diffuse latero-cervical lymphadenopathy. A (18)F-FDG-PET/CT scan showed many areas of intense (18)F-FDG uptake in multiple vertebrae, in some ribs, in the sacrum, in the liver, in both lungs, in multiple lymph nodes spread in the cervical, thoracic and abdominal chains. A bone marrow biopsy showed a "lymphomatoid granulomatosis", a rare variant of B-cell non-Hodgkin lymphoma (NHL). After the treatment, the (18)F-FDG-PET/CT scan showed a complete metabolic response.

Validation of flow cytometric phospho-STAT5 as a diagnostic tool for juvenile myelomonocytic leukemia.

To diagnose juvenile myelomonocytic leukemia (JMML) is sometimes challenging, because around 10% of patients lack molecular abnormalities affecting Ras-MAPK (mitogen-activated protein kinase) pathway and other diseases such as cytomegalovirus infection can mimic clinical signs of JMML. In order to validate a phospho-specific flow cytometry assay assessing phospho-signal transducer and activator of transcription factor 5 (p-STAT5) as a new diagnostic tool for JMML, we examined 22 samples from children with JMML and 47 controls. CD33+/CD34+ cells from 22 patients with JMML showed hyperphosphorylation of STAT5 induced by sub-saturating doses of granulocyte-macrophage colony-stimulating factor (GM-CSF). Using a training set of samples (11 JMML and 23 controls), we identified a threshold for p-STAT5-positive after stimulation with 0.1 ng/ml GM-CSF (17.17%) that discriminates JMML from controls. This threshold was validated in an independent series (11 JMML, 24 controls and 7 cases with diseases other than JMML) where we demonstrated that patients with JMML could be distinguished from other subjects with a sensitivity of 91% (confidence interval (CI) 59-100%) and a specificity of 87% (CI 70-96%). Positive and negative predictive values were 71% (CI 42-92%) and 96% (CI 82-100%), respectively. In conclusion, flow cytometric p-STAT5 profiling is a reliable diagnostic tool for identifying patients with JMML and can contribute to consistency of current diagnostic criteria.