Which of the following is not compatible with a diagnosis of juvenile myelomonocytic leukemia -

Ans. is 'c' i.e., Presence of bcr/abl fusion geneJuvenile myelomonocvtic leukemia (JMML) o Juvenile myelomonocytic leukemia (JMML) is a rare but distinct form of childhood leukemia, formerly called juvenile chronic myeloid leukemia (Juvenile CML).Most of the patients are less than 2 years of age.In contrast to adult CML, the cells in JMML do not contain Philadelphia chromosome and do not express bcr/abl fusion gene.Clinical featureso Children frequently present with complains of malaise, bleeding, or fever, often with localized infection.o Less common presentations include pulmonary symptoms (cough, wheezing), abdominal discomfo & distension, weight loss, splenomegaly, hepatomegaly, lymphadenopathy and eczematous skin rash.o Xanthoma and cafe - au - lait spots are often associated with JMML and JMML has been associated with neurofibromatosis type I in 11% of the cases.Laboratory findingso Peripheral blood --> Monocytosis (>1000/ 1), mild leukocytosis, thrombocytopenia, elevated fetal hemoglobin, elevated nuramidase, normal to diminished leukocyte alkaline phosphatase.o Bone marrow --> Hypercellularity with predominance of granulocytes at all stages of maturation, monocytosis, reduced megakaryocytes, increased blast count (but not to the level seen in acute leukemia).Chromosomal alteration :- monosomy 7 (-7q) in 25% of the cases.o A distinctive characteristic of JMML leukemic cells is their spontaneous proliferation in vitro due to their hypersensitivity to GM- CSF.