Alpha-mannosidosis is a rare disorder characterized by lack of muscle coordination, coarse facial features, skeletal abnormalities, hearing loss, and intellectual disability. This is due to the defective enzyme alpha-mannosidase. There are three forms of this disorder, separated by age of onset and severity of symptoms. The mild form typically begins to shows signs of the disease after age 10. Individuals with this form develop muscle weakness that slowly deteriorates as they get older. They typically do not have skeletal abnormalities and may survive into their fifties. People with the moderate form are usually identified before age 10 with skeletal abnormalities and more severe muscle weakness that will progress to a severe muscle problem between 20 and 30 years old. Survival is well into adulthood. In the most severe form, death occurs before birth or early in childhood due to rapid disintegration of their nervous system. These children will also have skeletal abnormalities. People with alpha-mannosidosis can also have frequent infections because their immune system doesn't work properly. There is no cure for alpha-mannosidosis; however medical surveillance and care may help to improve some symptoms and overall condition of life. Alpha-mannosidosis is caused by pathogenic variants in the MAN2B1 gene.