Key Inclusion Criteria for both ALSP patients and asymptomatic carriers:  1. Subjects who have documentation of a gene mutation in the CSF1R gene  Key Inclusion Criteria for ALSP patients, only:  Subjects who fulfill both of the following criteria (a and b):  a. One or more findings of clinical signs or symptoms in the following categories: i. Cognitive impairment or psychiatric problem ii. Pyramidal signs on neurological examination iii. Extrapyramidal signs, such as rigidity, tremor, abnormal gait, or bradykinesia iv. Epilepsy b. Findings consistent with ALSP on MRI. NOTE: Subjects with other causes of leukoencephalopathy, including vascular dementia, multiple sclerosis, or leukodystrophy (e.g., adrenoleukodystrophy, Krabbe disease, metachromatic leukodystrophy), will be excluded.  Subjects who, in the investigator's opinion, have demonstrated clinical progression of their ALSP within the past year. Subjects who have a cognitive or motor impairment that can affect their ability to comply with study requirements must have a designated caregiver who spends at least 4 hours per week with them. The caregiver must be able and willing to assist the subject in complying with the study requirements, be able to provide information during study visits, and be willing to sign a caregiver ICF.  Key Exclusion Criteria (for all study participants):  Subjects with any neurological or psychiatric diseases that can produce cognitive, motor, or behavioral impairment similar to ALSP, including, but not limited to, Alzheimer's disease, frontotemporal dementia, ALS, stroke, Huntington disease, multiple sclerosis, Parkinson's disease, and Down syndrome, or with active alcohol/drug abuse Subjects who are unable to undergo MRI Subjects with any condition or situation that, in the opinion of the investigator or sponsor medical personnel, may place the subject at significant risk, confound the study results, or interfere significantly with the subject's participation in the study. Subjects who have previously undergone HSCT within 12 months prior to Screening/Baseline