Purpose: To develop a prognostic system for transplantation-age patients with primary myelofibrosis (PMF) that integrates clinical, cytogenetic, and mutation data. Patients and Methods: The study included 805 patients with PMF age ≤ 70 years recruited from multiple Italian centers and the Mayo Clinic (Rochester, MN), forming two independent learning and validation cohorts. A Cox multivariable model was used to select from among a list of 22 variables those that were predictive of overall survival (OS). Integrated clinical and genetic prognostic models with (MIPSS70-plus) or without (MIPSS70) cytogenetic information were developed. Results: Multivariable analysis identified the following as significant risk factors for OS: hemoglobin < 100 g/L, leukocytes > 25 × 10⁹/L, platelets < 100 × 10⁹/L, circulating blasts ≥ 2%, bone marrow fibrosis grade ≥ 2, constitutional symptoms, absence of CALR type-1 mutation, presence of high–molecular risk mutation (ie, ASXL1, EZH2, SRSF2, IDH1/ 2), and presence of two or more high–molecular risk mutations. By assigning hazard ratio (HR)–weighted points to these variables, three risk categories were delineated for the MIPSS70 model; 5-year OS was 95% in low-risk, 70% in intermediate-risk, and 29% in high-risk categories, corresponding to median OS of 27.7 years (95% CI, 22 to 34 years), 7.1 years (95% CI, 6.2 to 8.1 years), and 2.3 years (95% CI, 1.9 to 2.7 years), respectively. In the MIPSS70-plus model, which included cytogenetic information, four risk categories were delineated, with 5-year OS of 91% in low-risk, 66% in intermediate-risk (HR, 3.2; 95% CI, 1.9 to 5.2), 42% in high-risk (HR, 6.4; 95% CI, 4.1 to 10.0), and 7% very high–risk categories (HR, 17.0; 95% CI, 9.8 to 29.2). Both models remained effective after inclusion of older patients in the analysis. Conclusion: MIPSS70 and MIPSS70-plus provide complementary systems of risk stratification for transplantation-age patients with PMF and integrate prognostically relevant clinical, cytogenetic, and mutation data.

The rapid induction of interferon-γ (IFN-γ) by innate cytokines such as interleukin 12 (IL-12) and IL-18 is critical for immunity against infectious pathogens. We investigated the molecular mechanisms underlying this response. IL-12 and IL-18 rapidly and synergistically induced the secretion of IFN-γ by freshly purified human peripheral blood lymphocytes. At early time points, IFN-γ was expressed almost exclusively by natural killer cells and in both CD56^bright and CD56^dim subpopulations. Mitogen-activated protein kinase p38 was activated strongly by IL-18 and weakly by IL-12 in natural killer cells but was not activated by either cytokine in T cells. The expression of IFN-γ mRNA and protein was dose-dependently blocked by SB203580, a specific inhibitor of mitogen-activated protein kinase p38, which also caused a dramatic destabilization of IFN-γ mRNA. The 3′ untranslated region (UTR) of IFN-γ mRNA conferred p38 responsiveness to a heterologous reporter mRNA. Therefore, the synergistic induction of IFN-γ by IL-12 and IL-18 in natural killer cells is mediated at least in part by p38-dependent and 3′ UTR-mediated stabilization of IFN-γ mRNA. (Blood. 2005;105:282-288)

Key Points: Patients with PMF may carry JAK2 (V617F), a CALR exon 9 indel, an MPL exon 10 mutation, or none of these genetic lesions. The genetic subtypes of PMF differ substantially as regards clinical course, disease progression, and overall survival.

A quarter of patients with essential thrombocythemia or primary myelofibrosis carry a driver mutation of CALR, the calreticulin gene. A 52-bp deletion (type 1) and a 5-bp insertion (type 2 mutation) are the most frequent variants. These indels might differentially impair the calcium binding activity of mutant calreticulin. We studied the relationship between mutation subtype and biological/clinical features of the disease. Thirty-two different types of CALR variants were identified in 311 patients. Based on their predicted effect on calreticulin C-terminal, mutations were classified as: (i) type 1-like (65%); (ii) type 2-like (32%); and (iii) other types (3%). Corresponding CALR mutants had significantly different estimated isoelectric points. Patients with type 1 mutation, but not those with type 2, showed abnormal cytosolic calcium signals in cultured megakaryocytes. Type 1-like mutations were mainly associated with a myelofibrosis phenotype and a significantly higher risk of myelofibrotic transformation in essential thrombocythemia. Type 2-like CALR mutations were preferentially associated with an essential thrombocythemia phenotype, low risk of thrombosis despite very-high platelet counts and indolent clinical course. Thus, mutation subtype contributes to determining clinical phenotype and outcomes in CALR-mutant myeloproliferative neoplasms. CALR variants that markedly impair the calcium binding activity of mutant calreticulin are mainly associated with a myelofibrosis phenotype.

Few investigators have evaluated the usefulness of the JAK2 V617F mutation for explaining the phenotypic variations and for predicting the risk of major clinical events in primary myelofibrosis (PMF). In a transversal survey we assayed by allele-specific polymerase chain reaction (PCR) the JAK2 V617F mutational status in 304 patients with PMF. Multiple DNA samples were collected prospectively from 64 patients, and a highly sensitive quantitative PCR was used as a confirmatory test. In a longitudinal prospective study we determined the progression rate to clinically relevant outcomes in 174 patients who had JAK2 mutation determined at diagnosis. JAK2 V617F was identified in 63.4% of patients. None of the V617F-negative patients who were sequentially genotyped progressed to become V617F positive, whereas progression rate from heterozygous to homozygous mutation was 10 per 100 patient-years. JAK2 V617F mutation contributed to hemoglobin, aquagenic pruritus, and platelet count variability, whereas homozygous mutation was independently associated with higher white blood cell count, larger spleen size, and greater need for cytoreductive therapies. Adjusting for conventional risk factors, V617F mutation independently predicted the evolution toward large splenomegaly, need of splenectomy, and leukemic transformation. We conclude that JAK2 V617F genotype should be considered in any future risk stratification of patients with PMF.

Hemophagocytic lymphohistiocytosis (HLH) is characterized by immune dysregulation due to inadequate restraint of overactivated immune cells and is associated with a variable clinical spectrum having overlap with more common pathophysiologies. HLH is difficult to diagnose and can be part of inflammatory syndromes. Here, we identify a novel hematological/autoinflammatory condition (NOCARH syndrome) in four unrelated patients with superimposable features, including neonatal-onset cytopenia with dyshematopoiesis, autoinflammation, rash, and HLH. Patients shared the same de novo CDC42 mutation (Chr1:22417990C>T, p.R186C) and altered hematopoietic compartment, immune dysregulation, and inflammation. CDC42 mutations had been associated with syndromic neurodevelopmental disorders. In vitro and in vivo assays documented unique effects of p.R186C on CDC42 localization and function, correlating with the distinctiveness of the trait. Emapalumab was critical to the survival of one patient, who underwent successful bone marrow transplantation. Early recognition of the disorder and establishment of treatment followed by bone marrow transplant are important to survival.