I plan to soon introduce a resolution designating the month of September 2025 as “Histiocytosis Awareness Month” in Pennsylvania.
Histiocytosis is a general term for a group of rare disorders that occur when there is an over-production of white blood cells known as histiocytes, which can lead to organ damage and tumor formation.
In 1987, the Histiocyte Society first classified histiocytic disorders into three categories. However, in 2016, the society revised this classification, organizing the disorders into five main groups based on new research findings:
- L Group: Langerhans-related histiocytosis
- C Group: Cutaneous and mucocutaneous histiocytosis
- R Group: Rosai–Dorfman disease (RDD)
- M Group: Malignant histiocytosis
- H Group: Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome
The classification has helped create a common language for diagnosis and treatment, leading to international collaboration through clinical studies. Over the past 15 to 20 years, research supported by the Histiocytosis Association has advanced the understanding of these disorders. Based on discoveries of cancer-causing mutations in many cases, the World Health Organization has classified a few of the disorders as rare cancers, known as histiocytic neoplasms.
Histiocytic disorders are very rare and therefore not widely recognized or understood by the general public or even within the medical community, despite the progress over the last two decades.
Please join me in co-sponsoring this important resolution to bring awareness to histiocytosis.