# Symptoms and Phases of Myelofibrosis
Myelofibrosis occurs in phases that can overlap and change both the physical symptoms and the severity of the disorder. The course varies greatly from person to person. The phases help doctors assess the severity and adjust the treatment.
Early phase (asymptomatic or milder symptoms)
In the early phase, many people have no complaints, or only very mild symptoms. The disease is often discovered by chance during a routine blood test.
**Symptoms that may occur:**
- No symptoms (discovered by accident)
- Mild tiredness
- A feeling of fullness in the upper left abdomen due to an enlarged spleen
- Possible slight night sweats or feeling hot
**What this means for daily life: **
Many people still feel completely normal in this phase and can continue their work and daily life without disability. When there are symptoms, it is usually mild fatigue that does not affect activities.
**Details about this phase: **
In the early phase, people without symptoms can remain without treatment for years. For some, the disease progressed slowly. This depends on personal risk factors and disease rates in the blood and bone marrow. Studies from 2025-2026 show that the time to start treatment depends on the individual prognosis — not all patients start at the same time.
Intermediate phase
In this phase, symptoms increase and the bone marrow is progressively damaged. The blood values are becoming more abnormal.
**Symptoms that may occur:**
- Marked tiredness and reduced exercise tolerance
- Night sweats, sometimes so intense that clothes need to be changed
- Fever (usually mild, occurring without infection)
- Pain or fullness under the left side of the ribs (due to enlargement of the spleen and/or liver)
- Weight loss without clear reason
- Leg pain and bone mine (from the bone marrow itself)
- Itching, especially after hot water (rare but annoying)
- Bruises or bruises faster than before
- More infections due to a decrease in certain white blood cells
- Constipation or diarrhoea due to enlarged spleen
**What this means for daily life: **
The tiredness can be significant and limit work, hobbies and social activities. Night sweats interfere with sleep. The pain below the left side can make it difficult to carry bags or certain body positions. Many people need treatment in this phase to better control symptoms.
**Details about this phase: **
The duration of the intermediate phase varies very significantly between people. Recent study programs (2025-2026) show that the time of progression depends on genetic factors, risk classification and personal blood values. Prognosis and survival are determined by a combination of factors; individual differences are significant.
Advanced phase (disease with severe bone marrow damage)
As the bone marrow is increasingly destroyed, blood values deteriorate sharply. This can lead to deep anaemia (anaemia), too few white blood cells, and bleeding trends.
**Symptoms that may occur:**
- Severe, disabling tiredness that severely restricts daily life
- Considerable weight loss
- Frequent infections (due to very low levels of certain white blood cells)
- Bleeding: nasal bleeding, gum blood, unexplained bruising, sometimes severe
- Severe night sweats with changes of clothes and sheets
- Breathlessness during exercise (due to severe anaemia)
- Chest pain, heart palpitations (from the same cause)
- Large spleen and/or liver enlargement with a strong gut feeling
- Possible thrombosis (blood clot) in abdominal vessels — this can suddenly cause severe abdominal pain
- Possible development of additional blood-forming hairs outside the bone marrow (extramedullary hematopoiesis), which can be felt as growths
**What this means for daily life: **
Most daily activities become very difficult or impossible. Many patients are dependent on frequent transfusions and hospital visits. Work is usually no longer possible. The focus is shifting to symptom relief and hospital management.
**Details about this phase: **
A recent analysis from 2026 shows that treatment with JAK inhibitors (such as ruxolitinib and newer agents like fedratinib, pacritinib, and momelotinib) can relieve symptoms in this phase, but survival and response vary strongly between individuals. Stem cell transplantation may be an option for certain patients. Median survival varies depending on prognosis at baseline: patients with low-intermediate risk have different prospects than those with high risk. Population data show that without treatment survival is shorter; with modern therapies, figures have improved, but large differences between individuals remain. This data cannot be applied to one person.
Phase with acute leukaemic transformation
Rarely (approximately 5-10% of patients) myelofibrosis transforms to acute myeloid leukaemia. This is a sudden worsening.
**Symptoms that may occur:**
- Sudden deterioration of general wellbeing
- Very high fever
- Severe infections
- Massive bleeding
- Rapidly rising numbers of blasts (immature cells) in the blood
- Possible organ dysfunction (renal stress, hepatic decline)
**What this means for daily life: **
This is a medical emergency. Patients are admitted to hospital for intensive care. Treatment aims for remission, but prognosis is more cautious than in the previously mentioned phases.
**Details about this phase: **
Leukaemic transformation occurs in approximately 5-10% of all myelofibrosis patients at some point during their illness. This is associated with certain genetic mutations and disease scores at diagnosis. Median survival after transformation is shorter than in earlier phases; recent studies (2025-2026) are working on better treatments, but individual outcomes remain very diverse.
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When to contact your healthcare provider
Contact your doctor or go to the emergency department if:
- You suddenly experience severe abdominal pain with nausea and vomiting (possible thrombosis)
- You have serious blood loss (spitting up large amounts of blood, bloody or black stools, very heavy menstruation)
- You develop fever above 38.5°C with chills
- You experience severe shortness of breath or chest pain
- You experience severe headache, confusion or speech problems
- Your fatigue suddenly becomes much worse and you feel very unwell
- Your bleeds do not stop or occur increasingly easily
_This information never replaces a doctor's judgment. Always discuss your situation with your own healthcare provider._