Circulating immune complexes in myelofibrosis

17 patients with idiopathic myelofibrosis were studied for the occurrence of circulating immune complexes (IC), using a polyethylene glycol complement consumption and a polyclonal rheumatoid factor inhibition assay. In 13 patients complement C3d was determined by rocket immunoelectrophoresis. Circulating IC were detected in 6 patients and were primarily found in patients with short duration of disease from time of diagnosis. The median duration of the disease in IC‐positive patients was 4 months, compared to 12 months in the IC‐negative group (P<0.05). 9 of the 13 patients investigated had increased levels of plasma C3d. However, there was no correlation to the occurrence of IC. It is concluded that circulating IC may take part in an immune‐mediated bone marrow damage. This may involve deposition of IC in the bone marrow with secondary inflammation responsible for the development of bone marrow fibrosis.