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.