The aim of the study is to classify CSF1R-RD into six distinct clinical stages from 0 to 5, based on the spectrum of clinical presentations.

CSF1R-RD is a rare hereditary condition. The most common monoallelic form of CSF1R-RD is inherited in an autosomal dominant manner. The prevalence of CSF1R-RD remains unknown but is likely underestimated. To aid in diagnosis, specific criteria for CSF1R-RD were established in 2015, facilitating the identification of cases warranting genetic testing. The most frequent misdiagnoses include multiple sclerosis, frontotemporal dementia, and nonspecific dementia. Although diagnostic standards exist, a unified clinical assessment tool for CSF1R-RD has yet to be developed. Such a system would help stratify patients and guide selection for clinical trials.

The classification of CSF1R-RD into six distinct clinical stages from 0 to 5 was based on the spectrum of clinical presentations (cognitive and motor symptoms) and current knowledge regarding biomarker utility in this disease (radiological and cerebrospinal fluid). 

Stages 0 and 1 refer to asymptomatic individuals, with the distinction that Stage 1 includes those in whom early disease processes can be identified through positive biomarker findings (stages 1a-1c), or in whom biomarkers have not been tested (stage 1x). Stages 2 through 5 represent clinical phases (early symptomatic, mild, moderate, severe respectively). Clinical phases can be distinguished as mostly cognitive, motor or mixed phenotype.

This classification provides a comprehensive assessment of patients with CSF1R-RD and is tailored to the needs of clinicians and researchers working with this condition. Using this staging system in real-world clinical situations will allow for the assessment of its effectiveness and clinical utility.