Rationale for StudyPrimary Myelofibrosis (PMF) mainly affects individuals in their sixth decade of life or older. It is the most difficult myeloproliferative neoplasm to be defined, as the phenotype mimics a variety of hematological and non-hematological diseases. No symptom or sign is specific for PMF. Many patients are asymptomatic at presentation and the disease is usually detected by the discovery of a splenomegaly or abnormal blood counts during a routine examination. The only treatment with curative potential for PMF is allogeneic stem cell transplantation. This should be reserved only for high-risk patients, after careful consideration, taking into account the option for participation in clinical trials of new drugs. It is therefore extremely important the early identification of poor prognosis patients, to offer the best therapy. In Brazil, we do not have sufficient data to assess a patient's journey between the first symptoms and diagnosis of PMF. Moreover, the real incidence/ prevalence of this disease is unknown and a sub-diagnosis rate is speculated in our country. ObjectivesUnderstand and identify the journey of patients with PMF (clinical characteristics, diagnosis process and therapeutics interventions) and the problems between the first symptoms and initiation of treatment. MethodsGiven the observational nature of the study and the lack of a specific hypothesis to be tested, the statistical analysis is descriptive. This partial analysis includes descriptive results of contents of the database. Categorical data are presented as frequencies and percentages. For continuous data, mean, standard deviation, median, minimum, and maximum values are presented. Results103 patient disposition (2008-2012); all of them met WHO criteria 2008: median age: 69; 58% male and 13.6% had died. Based on medical history, professional or environmental exposure was related in 4%, but this information was lack in 25% of the medical charts. In almost 42% of the medical records, the family history was not available. Two patients had a positive family history (brother of one and sister from another one with the same disease). Most frequent reason (63,1%) for medical evaluation seeking was symptoms and fatigue happened in 67% of them. Time from symptoms onset date until the confirmed diagnosis took a median of 9.7 months. General physician was the most frequent specialist to do the first evaluation of the patient until confirmed or suspected diagnosis. Bone marrow aspiration and bone marrow biopsy were performed in all patients; mutation status for JAK V617F in 82.5%, PCR for BCR-ABL in 71.8% and bone marrow cytogenetics in 64.1%. According to IPSS (78 patients), 8.5 % were low risk, 63.4% intermediate-1 63.4%, intermediate-2 28.1% and none high risk. Anemia was the most frequent laboratorial finding (67%) and most of the patients were treated with hydroxiurea (75.7%). ConclusionsAlthough most of the patients have apparently the diagnosis of PMF, it took almost 10 months to be done. An expressive number of medical reports do not show a complete history, while 20-30% of them don't have all the laboratory tools for a precise diagnosis. It is important to know Brazilian needs to improve diagnostic and provide a better treatment, since we are facing new drugs for PMF. Disclosures:No relevant conflicts of interest to declare.