Widening of incisor spacing is one of the symptoms of mannosidosis type II. Mannosidosis type II most often develops after 2 years of age with normal physical and psychomotor development, progressive brain growth retardation starting after 2 years of age, frequent respiratory infections, ugly face, thick eyebrows, widened incisor spacing, convex jaw, low anterior hairline, and mild bilateral deafness (mostly sensory). Some patients may have allodynia. The etiology is mainly a genetic defect, and the patient has an acidic alpha;-mannosidase defect. The main cause of deafness is a genetic defect and a defect in the patient’s acidic alpha-mannosidase enzyme. It is a systemic disease caused by alpha-mannosidase deficiency with clinical features similar to Hurler syndrome, without mucopolysaccharidosis but with increased mannose-containing components in the tissues. Normally, this enzyme hydrolyzes oligosaccharide alpha-bonded mannosides. Because of the defective acidic alpha-mannosidase in this disease, glycoproteins cannot be broken down and mannose-rich oligosaccharides are deposited in the tissues, mainly in the brain, and excreted in the urine. The swollen neurons in the brain are balloon-like, and the deposited material is mannose-containing glycoproteins.