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Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an ultra-rare neurodegenerative disorder caused by autosomal dominant mutations in the CSF1Rgene, with the global prevalence is about 300 cases per million people. This progressive multisystem disease typically manifests between 30-50 years of age, characterized by cognitive decline, neuropsychiatric symptoms (including depression and psychosis), and motor impairments such as parkinsonism, spasticity, and ataxia. Diagnostic hallmarks include symmetric frontal-parietal white matter abnormalities and brain atrophy on MRI, along with distinctive pathological findings of axonal spheroids and pigmented glial cells.

Supplementary Explanation on the Naming of ALSP: Initially described in 1984 as "Hereditary Diffuse Leukoencephalopathy with Spheroids (HDLS)", the disease was later linked to CSF1R mutations in 2011. The term "Adult-onset Leukoencephalopathy with Axonal Spheroids and Pigmented Glia (ALSP)" was adopted to better reflect its key features: adult onset, white matter damage with axonal spheroids, and pigmented glial cells. This shift unified earlier terms like HDLS and "Pigmentary Orthochromatic LeukoDystrophy (POLD)", emphasizing its neurodegenerative (rather than metabolic) nature.