CSF1R and Hereditary diffuse leukoencephalopathy with axonal spheroids and pigmented glia: In 2011, it was discovered that heterozygous mutations in the colony stimulating factor-1 receptor (CSF1R) gene cause HDLS.1 In addition, it was shown that pigmented orthochromatic leukodystrophy (POLD) is also caused by CSF1R mutations and that POLD and HDLS exist on a spectrum.2 Previous studies have estimated that CSF1R mutations account between 10% and 25% of adult onset leukodystrophies, depending on the population studied.3, 4