Platelet‐associated IgG and IgM in myelofibrosis

Elevated levels of platelet‐associated IgG and/or IgM were found in 15 of 18 patients with myelofibrosis (83 %). All but 5 patients with elevated PAIg had active disease. The amounts of PAIg were not correlated to either S‐Ig, platelet count or spleen size. Levels of PAIgG well above the normal range were especially found in patients with short duration of disease and/or a transitional myeloproliferative state. It is debated whether immune‐mediated platelet dysfunction may be of importance for the development of bone marrow fibrosis, mediated by the release of platelet‐derived growth factors in the bone marrow. Elevated PAIg may also contribute to abnormal haemostasis and thrombocytopenia in myelofibrosis.