Question: What is (are) Myelofibrosis ?
Answer: Myelofibrosis is a disorder of the bone marrow, in which the marrow is replaced by fibrous (scar) tissue. Scarring of the bone marrow causes anemia, which can lead to fatigue and weakness, as well as pooling of the blood in abnormal sites like the liver and spleen, causing these organs to swell. Although myelofibrosis can occur at any age, it typically develops after the age of 50. In most cases, myelofibrosis gets progressively worse. Treatment is aimed at relieving signs and symptoms and may include medications, blood transfusions, chemotherapy, radiation therapy and surgery.
Source: GARD

Question: What are the symptoms of Myelofibrosis ?
Answer: What are the signs and symptoms of Myelofibrosis? The Human Phenotype Ontology provides the following list of signs and symptoms for Myelofibrosis. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Autosomal dominant inheritance - Myelofibrosis - Myeloproliferative disorder - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD