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A trombocitemia essencial ou trombocitose essencial é uma desordem mieloproliferativa crônica, caracterizada pela proliferação clonal de megacariócitos na medula óssea (mo), levando ao aumento persistente das plaquetas circulantes, com rearranjo brc/abl negativo. o nível plaquetário encontrado na doença é acima de 400 x 10^9/l, clinicamente cursando com esplenomegalia e episódios trombóticos e/ou hemorrágicos, entretanto na infância geralmente é assintomático. A incidência da doença é rara e a idade média ao diagnóstico está entre 50 e 60 anos, sendo um achado extremamente incomum na infância, com prognóstico bom na fase adulta e reservado na faixa etária pediátrica.

A Hemoglobina Paroxística Noturna (HPN) é uma doença hematológica rara, clonal e adquirida, caracterizada por anemia hemolítica intravascular, episódios trombóticos e pancitopenia (graus variáveis de insuficiência medular). Desordem clonal, causada por mutação somática adquirida do gene PIG-A (fosfatidilinositol glicano da Classe A), ligado ao cromossomo X, afeta a célulatronco hematopoiética responsável pela produção de todas as células do sangue. Devido à raridade da doença, os dados epidemiológicos são escassos, com incidência estimada de 0.3-100.000 habitantes-ano e a prevalência de 1,59 casos por 100.000 habitantes e na faixa etária pediátrica, na qual corresponde a 10% da já rara incidência em adultos (de 1 em 10^5 a 1 em 10^6).

LMA apresenta uma translocação (8;16) (p11; p13) que gera a fusão gênica MYST3-CREBBP, que é mais comumente vista em adultos. Essa translocação (8;16) (p11; p13) está associada à idade precoce, diferenciação monocítica e hemofagocitose e sendo indicativo de pior prognóstico. Método: série de 266 casos de LMA em pacientes pediátricos no período de 2003 a 2012. Foram incluídas crianças com menos de 2 anos de idade, com LMA e presença de hemofagocitose. Foram incluídos 48 casos de LMA sem hemofagocitose. O método de hibridização fluorescente in situ (FISH) para os rearranjos MLL foi realizado ao diagnóstico, assim como o FISH para rearranjo MYST3-CREBBP. Resultados: dos casos analisados, 5 estavam associados à fusão MYST3-CREBBP e tinham associação com: hepatoesplenomegalia, lesões de pele ou cloroma localizados. Discussão: a alta frequência de LMA MYST3-CREBBP em bebês (idade < 24 meses) e casos de LMA congênita favorecem a hipótese de que a leucemia ocorre durante a vida intrauterina e pode ser utilizada para explorar melhor o entendimento da leucemogênese da LMA. Publicado na Rev. Bras. Hematol hemoter. 2016;38(4):291–297, com mesmo título. Autores: Francianne Gomes Andrade, Elda Pereira Noronha, Rosania Maria Baseggio, Teresa Cristina Cardoso Fonseca, Bruno Marcelo Rocha Freire, Isis M. Quezado Magalhães, Ilana R. Zalcberg, Maria S. Pombo-de-Oliveira.

Background and Aims The biological characterization of childhood acute myeloid leukemia (c-AML) is an important outcome predictor. In Brazil, very little is known about the frequency of AML subgroups, although c-AML accounts for about 18% of leukemias. We carried out this study to investigate the contribution of type I and II gene mutations in the probability of overall survival (pOS) of c-AML in Brazil. Methods Seven hundred and three de novo pediatric AML cases (2000–2015) were assessed throughout a multicentric network study. Mutations in hotspot regions of FLT3 , NRAS , KRAS , PTPN11 , and c- KIT genes were analyzed as well as fusion genes ( RUNX1 - RUNX1T1 , MLL / KMT2A -r, CBFβ - MYH11 , and PML - RARα ) associated with AML. Patients were treated out of the clinical trial although following the BFM-AML2004 protocol. Acute promyelocytic leukemia (APL) was treated differently. AML with Down syndrome was excluded. Results There were significant differences in gene mutations among age ranges (≤2 years-old; >2–10 years old and ≥11 years old) and the nonrandom association between type I/II mutations. Lower white blood cell count (≤50 × 10 9 /L) was associated with RUNX1 - RUNX1T1 , whereas higher WBC with CBFβ-MYH11 ( p p = 0.03). pOS differences were observed between Brazilian regions. The South-Southeast regions had a better 5-year pOS, whereas the Midwest region presented the poorest pOS (23.7 ± 4.9%). PTPN11 mutations conferred an adverse prognosis as an independent prognostic factor. Conclusions Identification of genetic subgroups contributes to the molecular epidemiology and biology of AML worldwide, reflecting the profile of pediatric AML cases in Brazil.

The understanding of leukemogenesis in early-age acute leukemia (EAL) has improved remarkably. Initiating somatic mutations detected in dried neonatal blood spots (DNBS) and in cord blood samples of affected children with leukemia have been proven to be acquired prenatally. However, to date, few epidemiological studies have been carried out exploring EAL that include infants and children 13–24 months of age at the diagnosis. Maternal exposure to transplacental DNA-damaging substances during pregnancy has been suggested to be a risk factor for EAL. Most cases of infants with acute lymphoblastic (i-ALL) or myeloid leukemia (i-AML) have KMT2A gene rearrangements ( KMT2A-r ), which disturb its essential role as an epigenetic regulator of hematopoiesis. Due to the short latency period for EAL and the fact that KMT2A-r resembles those found in secondary AML, exposure to topoisomerase II inhibitors has been associated with transplacental risk as proxi for causality. EAL studies have been conducted in Brazil for over two decades, combining observational epidemiology, leukemia biology, and clinical data. EAL was investigated considering (i) age strata (infants vs. 13–24 months-old); (ii) somatic mutations associated with i-ALL and i-AML; (iii) ethnic-geographic variations; (iv) contribution of maternal genotypes; and (v) time latency of exposures and mutations in DNBS. Interactions of acquired and constitutive gene mutations are challenging tools to test risk factor associations for EAL. In this review we summarize the EAL scenario (including B-cell precursor-ALL, T-ALL, and AML) results combining environmental and genetic susceptibility risk factors and we raise questions that should be considered for further action.

Background Acute myeloid leukemia presenting the MYST3-CREBBP fusion gene is a rare subgroup associated with hemophagocytosis in early infancy and monocytic differentiation. The aim of this study was to define the relevant molecular cytogenetic characteristics of a unique series of early infancy acute myeloid leukemia cases (≤24 months old), based on the presence of hemophagocytosis by blast cells at diagnosis. Methods A series of 266 infant cases of acute myeloid leukemia was the reference cohort for the present analysis. Acute myeloid leukemia cases with hemophagocytosis by blast cells were reviewed to investigate the presence of the MYST3-CREBBP fusion gene by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction. Results Eleven cases with hemophagocytosis were identified with hemophagocytic lymphohistiocytosis being ruled out. Six cases were classified as myelomonocytic leukemia, three as AML-M7 and two as AML-M2. In five cases, the presence of the MYST3-CREBBP fusion gene identified by molecular cytogenetics was confirmed by fluorescence in situ hybridization. All patients received treatment according to the Berlin–Frankfurt–Munster acute myeloid leukemia protocols and only one out of the five patients with the MYST3-CREBBP fusion gene is still alive. Conclusions Our findings demonstrate that the presence of hemophagocytosis in acute myeloid leukemia was not exclusively associated to the MYST3-CREBBP fusion gene. Improvements in molecular cytogenetics may help to elucidate more complex chromosomal rearrangements in infants with acute myeloid leukemia and hemophagocytosis.