A new study has determined that indolent systemic mastocytosis (SM) has a higher prevalence than advanced SM and that patients with indolent SM have better overall survival than those with advanced SM.

The study, published in Cancers, also found the prevalence of SM in the Stockholm, Sweden, region to be 1 in 10,000 adults.

“In the present study, we describe the clinical and laboratory characteristics as well as the survival outcomes of patients with SM who were diagnosed and followed up at the Mastocytosis Center of Karolinska University Hospital over the last 15 years,” the authors wrote. “As we have previously reported on the allergological features of SM patients in detail, in the present study we aim to create a better understanding of the ways in which patients present to us, and consequently improve the diagnostic and follow-up processes.”

The research team retrospectively studied a cohort of 195 patients with SM at a single center in Stockholm between 2006 and 2020. They had a median follow-up time of 7.5 years. The patients were censored at death or the final follow-up, and their overall survival and risk factors for mortality were assessed.

Read more about SM epidemiology

In the cohort, the researchers found prevalences of 88.2% for indolent SM and less than 12% for advanced SM, which is comparable to other studies comparing the 2 types of disease. The median diagnostic delay was 10 years, and the prevalence of SM in the region was just over 10 per 100,000 adults, which is consistent with other European studies.

Patients with indolent SM had a favorable prognosis in terms of overall survival compared to those with advanced SM, and age at diagnosis and increased levels of tryptase, beta-2-microglobulin, and alkaline phosphatase were independent predictors of mortality.

Due to the heterogeneous nature of the disease, the authors recommend a multidisciplinary approach at specialized centers for patients with SM.


Ungerstedt J, Ljung C, Klimkowska M, Gülen T. Clinical outcomes of adults with systemic mastocytosis: a 15-year multidisciplinary experience. Cancers (Basel). Published online August 16, 2022. doi.10.3390/cancers14163942