SM and other types of mastocytosis are more common than previously reported

The higher rate was due to better diagnostics.

A new study found that the incidence of mastocytosis — including systemic mastocytosis (SM) — was significantly higher in adults than previously reported, according to results published recently in the European Journal of Epidemiology.

The study found 27.43 cases of mastocytosis per 100,000 adults in Denmark as of 2022, compared with a 25-year average rate of 1.21 per 100,000 individuals, the study said. Women accounted for 57.6% of cases, and the median age at diagnosis was 49 years.

Systemic mastocytosis (SM) is a rare hematological disease characterized by mast cells that are overactive and accumulate in different parts of the body such as the bone marrow, liver, spleen, gastrointestinal tract and lymph nodes.

The study attributed the increase to growing awareness and advancements in diagnostic techniques over recent decades.

Read more about SM causes and risk factors

“The prevalence of mastocytosis among adults in the Danish population is higher than previously found which is expectable with the general good survival among the majority of the patients,” study authors said.

They added: “However, an increasing incidence rate reveals that more and more patients are being diagnosed each year. Thereby indicating that more awareness of the disease since the establishment of the Mastocytosis Centers of Excellence combined with better diagnostic methods have led to more cases of mastocytosis being detected.”

The most common forms of mastocytosis among 1,594 patients identified in the comprehensive study included maculopapular cutaneous mastocytosis (48.9% of cases) and indolent SM (30.6%).

Encouragingly, survival rates for patients with nonadvanced forms — such as maculopapular cutaneous mastocytosis, indolent SM and cutaneous mastocytosis — aligned closely with those of the general population.

Patients with advanced SM, including aggressive subtypes such as mast cell leukemia and SM with associated hematologic neoplasms, had poorer outcomes. The median survival time for mast cell leukemia patients was only 0.3 years. The disparity in outcomes underscored the critical need for early diagnosis and close monitoring to prevent disease progression.

Most patients with mastocytosis exhibited elevated tryptase levels, a hallmark diagnostic marker. The median tryptase level for the cohort was 20 ng/ml, but significantly higher values were observed in those with advanced forms, such as mast cell leukemia, where the median was 247 ng/ml.

During the study, 3.6% of patients with nonadvanced mastocytosis progressed to more severe forms, with a median time to progression of seven years. Older age at diagnosis and higher initial tryptase levels were associated with greater risk of disease advancement.

Importantly, survival outcomes varied widely by subtype. Patients with indolent SM, maculopapular cutaneous mastocytosis and cutaneous mastocytosis showed 10-year survival rates of more 86%. Those with advanced SM faced significantly worse odds, with survival rates dropping to 29.8% for SM with associated hematologic neoplasms. The results emphasized the importance of distinguishing mastocytosis subtypes to provide tailored care.

Advancements in diagnostic tools and growing awareness benefited patients by enabling earlier detection of nonadvanced mastocytosis. For patients, this meant fewer delays in receiving appropriate care and improved quality of life. As the incidence continues to rise, health care providers must remain vigilant to ensure timely interventions, study authors advised.

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