Primary myelofibrosis (PMF) is a rare bone marrow blood cancer. It is classified by the World Health Organization (WHO) as a type of myeloproliferative neoplasm, a group of cancers in which there is growth of abnormal cells in the bone marrow. This is most often associated with a somatic mutation in the JAK2, CALR, or MPL gene markers. In PMF, the healthy marrow is replaced by scar tissue (fibrosis), resulting in a lack of production of normal blood cells. Symptoms include anemia, increased infection and an enlarged spleen (splenomegaly). In 2016, prefibrotic primary myelofibrosis was formally classified as a distinct condition that progresses to overt PMF in many patients, the primary diagnostic difference being the grade of fibrosis. Signs and symptoms
The primary feature of primary myelofibrosis is bone marrow fibrosis, but it is often accompanied by:

Abdominal fullness related to an enlarged spleen (splenomegaly). Bone pain
Bruising and easy bleeding due to inadequate numbers of platelets
Cachexia (loss of appetite, weight loss, and fatigue)
Enlargement of both the liver and spleen
Fatigue
Gout and high uric acid levels
Increased susceptibility to infection, such as pneumonia
Pallor and shortness of breath due to anemia
In rarer cases, a raised red blood cell volume
Cutaneous myelofibrosis is a rare skin condition characterized by dermal and subcutaneous nodules. : 746

Causes
The underlying cause of PMF is unknown (idiopathic disease). There is an association between mutations to the JAK2, CALR, or MPL gene and myelofibrosis. Approximately 90% of those with myelofibrosis have one of these mutations and 10% carry none of these mutations.
Based on the most recent criteria, classification with APS requires one clinical and one laboratory manifestation:
Clinical:A documented episode of arterial, venous, or small vessel thrombosis — other than superficial venous thrombosis — in any tissue or organ by objective validated criteria with no significant evidence of inflammation in the vessel wall
1 or more unexplained deaths of a morphologically normal fetus (documented by ultrasound or direct examination of the fetus) at or beyond the 10th week of gestation and/or 3 or more unexplained consecutive spontaneous abortions before the 10th week of gestation, with maternal anatomic or hormonal abnormalities and paternal and maternal chromosomal causes excluded or at least 1 premature birth of a morphologically normal neonate before the 34th week of gestation due to eclampsia or severe pre-eclampsia according to standard definitions, or recognized features of placental insufficiency
Laboratory:Anti-cardiolipin IgG and/or IgM measured by standardized, non-cofactor dependent ELISA on 2 or more occasions, not less than 12 weeks apart; medium or high titre (i.e., > 40 GPL or MPL, or > the 99th percentile)
Anti-β2 glycoprotein I IgG and/or IgM measured by standardized ELISA on 2 or more occasions, not less than 12 weeks apart; medium or high titre (> the 99th percentile)
Lupus anticoagulant detected on 2 occasions not less than 12 weeks apart according to the guidelines of the International Society of Thrombosis and Hemostasis.There are 3 distinct APS disease entities: primary (the absence of any comorbidity), secondary (when there is a pre-existing autoimmune condition, most frequently systemic lupus erythematosus, SLE), and catastrophic (when there is simultaneous multi-organ failure with small vessel occlusion).According to a 2006 consensus statement, it is advisable to classify APS into one of the following categories for research purposes:

I: more than one laboratory criterion present in any combination;
IIa: lupus anticoagulant present alone
IIb: anti-cardiolipin IgG and/or IgM present alone in medium or high titers
IIc: anti-β2 glycoprotein I IgG and/or IgM present alone in a titer greater than 99th percentileThe International Consensus Statement is commonly used for Catastrophic APS diagnosis.