Trametinib in Treating Patients With Relapsed or Refractory Juvenile Myelomonocytic Leukemia

Inclusion Criteria: * Patients must be \>= 1 month and \< 22 years of age at the time of study entry * Patients must have had histologic verification of juvenile myelomonocytic leukemia (JMML) at original diagnosis and currently have relapsed or refractory disease; the diagnosis is made based on the following criteria * JMML category 1 (all of the following): the diagnostic criteria must include all features in category 1 and EITHER (i) one of the features in category 2 OR (ii) two features from category 3 to make the diagnosis * Splenomegaly * \> 1000 (1 x 10\^9/uL) circulating monocytes * \< 20% blasts in the bone marrow or peripheral blood * Absence of the t(9;22) or BCR/ABL fusion gene * JMML category 2 (at least one of the following if at least two category 3 criteria are not present): * Somatic mutation in RAS or PTPN11 * Clinical diagnosis of NF1 or NF1 gene mutation * Homozygous mutation in CBL * Monosomy 7 * JMML category 3 (at least two of the following if no category 2 criteria are met): * Circulating myeloid precursors * White blood cell count, \> 10 000 (10 x 10\^9/ uL) * Increased hemoglobin F for age * Clonal cytogenetic abnormality * GM-CSF hypersensitivity * Patients with refractory or relapsed JMML must have had at least one cycle of intensive frontline therapy or at least 2 cycles of a deoxyribonucleic acid (DNA) demethylating agent with persistence of disease, defined by clinical symptoms or th…