Raised urinary calmodulin levels in idiopathic myelofibrosis: possible implications for the aetiology of fibrosis.

Platelet growth factors (e.g. PDGF and TGF-beta) are thought to be pathogenetically important in the stromal reaction characteristic of idiopathic myelofibrosis (IM). We have investigated a possible pathogenetic role for a further platelet mitogen, calmodulin. Platelets are rich in calmodulin, of which 30-40% is releasable with a time course that differs from alpha-granule proteins. In IM urinary calmodulin concentrations were 3-fold those of the normals controls. We suggest that an abnormal release of calmodulin may occur from platelets/megakaryocytes in patients with IM, and that calmodulin should be considered, along with other growth factors, in the pathogenesis of marrow fibrosis.