Adult leukoencephalopathy caused by alpha-mannosidosis deficiency (MIM248500) is a recessive inherited lysosomal storage disease associated with decreased activity of alpha-mannosidase. This enzyme degrades oligosaccharides and glycoproteins in neural and visceral tissues. There are two different disease phenotypes, type-I or severe infantile phenotype and type 2, which progresses more slowly and is compatible with survival into adulthood. We report the case of a 51-year-old man with gait disorders beginning at the age of 40 years associated with leukoencephalopathy due to alpha-mannosidosis deficiency.