Increased IL6 plasma levels in indolent systemic mastocytosis patients are associated with high risk of disease progression.

Systemic mastocytosis (SM) is a heterogeneous disease with altered interleukin (IL)-6 and IL13 plasma levels. However, no study has simultaneously investigated the plasma levels of IL1β, IL6, IL13, CCL23 and clusterin in SM at diagnosis and correlated them with disease outcome. Here we investigated IL1β, IL6, IL13, CCL23 and clusterin plasma levels in 75 SM patients--66 indolent SM (ISM) and 9 aggressive SM--and analyzed their prognostic impact among ISM cases grouped according to the extent of hematopoietic involvement of the bone marrow cells by the KIT D816V mutation. Although increased IL1β, IL6 and CCL23 levels were detected in SM patients versus healthy controls, only IL6 and CCL23 levels gradually increased with disease severity. Moreover, increased IL6 plasma levels were associated with ISM progression to more aggressive disease, in particular among ISM patients with multilineal KIT mutation (ISM-ML), these patients also showing a higher frequency of organomegalies, versus other ISM-ML patients. Of note, all ISM patients who progressed had increased IL6 plasma levels already at diagnosis. Our results indicate that SM patients display an altered plasma cytokine profile already at diagnosis, increased IL6 plasma levels emerging as an early marker for disease progression among ISM cases, in particular among high-risk ISM patients who carry multilineage KIT mutation.