Leucemia Mielóide Crônica: história natural e classificação / Chronic Myeloide Leukemia: natural history and classification

A Leucemia Mielóide Crônica (LMC), cuja incidência é de um a dois casos para cada 100 mil habitantes por ano, corresponde de 15 por cento a 20 por cento das leucemias. É uma doença mieloproliferativa crônica clonal, caracterizada por leucocitose com desvio à esquerda, esplenomegalia e pela presença do cromossomo Philadelphia (Ph), que resulta da translocação recíproca e equilibrada entre os braços longos dos cromossomos 9q34 e 22q11, gerando a proteína híbrida BCR-ABL, com atividade aumentada de tirosino quinase. A proteína BCR-ABL está presente em todos os pacientes com LMC, e sua hiperatividade desencadeia liberação de efetores da proliferação celular e inibidores da apoptose, sendo sua atividade responsável pela oncogênese inicial da LMC. A doença evolui em três fases: crônica, acelerada e aguda. Na fase crônica (FC) ocorre proliferação clonal maciça das células granulocíticas, mantendo estas a capacidade de diferenciação. Posteriormente, num período de tempo variável, o clone leucêmico perde a capacidade de diferenciação e a doença passa a ser de difícil controle (fase acelerada - FA) e progride para uma leucemia aguda (crise blástica - CB). Nesse artigo discutimos a história natural e as definições das fases da doença, de acordo com os critérios mais utilizados.

Chronic myeloid leukemia (CML) is estimated at approximately 1 to 2 cases per 100,000 individuals and accounts for approximately 15 percent to 20 percent of all patients with leukemia. CML is a clonal disease characterized by balanced translocation between chromosomes 9 and 22 (Philadelphia chromosome). The resulting BCR-ABL gene has abnormal tyrosine kinase activity which stimulates cell growth and is responsible for the transformed phenotype of CML cells. The disease is characterized by a triphasic course that includes a chronic phase (CP), an accelerated phase (AP) and an acute or blastic phase (BP). Unless the disease is controlled or eliminated, patients progress to AP and BF in variable periods of time. Several staging classification systems are used for CML all of which were designed in the pre-imatinib era. In this article we discuss the natural history of CML and phase definitions according to the most useful criteria.

Diagnostic role of conventional cytogenetics and fluorescence in situ hybridization (FISH) in chronic myeloid leukemia patients.

INTRODUCTION: The limitation of cytogenetic analysis is that the Ph chromosome cannot be detected in clumped metaphase or in interphase cells. Fluorescence in situ hybridization (FISH) is a highly sensitive molecular genetic technique, which enables to detect break point cluster region--Abelson (BCR-ABL) complex and minimal residual disease in all Ph positive CML patients not only in metaphase but also in interphase cells. AIMS: To detect Ph chromosome in CML patients by the use of conventional cytogenetics and FISH. MATERIAL AND METHODS: The bone marrow samples were collected in heparinised syringe from 35 diagnosed CML patients and transported to cytogenetic laboratory for chromosomal analysis. Conventional karyotype was prepared by direct harvesting and short-term culture. The FISH analysis was carried out on interphase cells of two patients to confirm the cytogenetic diagnosis. RESULTS: Out of 35 CML patients, 17 (49.9%) were 100% Philadelphia positive, 10(28.5%) were 50-70% Ph+ mosaics and 3(9%) were 100% Ph negative. In 5 patients (14.25%) cytogenetic analysis failed to confirm the presence or absence of Ph chromosome. FISH was carried out in interphase cells from bone marrow preparations of two patients. The signals for BCR-ABL fusion gene was absent in Ph- negative CML patients. In Ph positive patients, the FISH analysis detected BCR-ABL fusion gene seen as a yellow signal on interphase cells. CONCLUSION: Conventional cytogenetics is a useful method for detection of Ph chromosome in metaphase stage of cell division. FISH can be used in interphase stage of cell division for the same purpose.

Formas variantes de la leucemia mieloide crónica / Several form of the chronic myeloid leukemia

Se presentan las diferentes variantes de la leucemia mieloide crónica en cuanto a incidencia, edad, citogenética, pronóstico y respuesta terapeutica