Electron micrograph of a vacuolated lymphocyte. Electron micrograph of a vacuolated lymphocyte from a mannosidosis patient (A) as compared to a lymphocyte from a normal control (B). Figure 2 A defective<unk> -mannosidase enzyme, which normally helps to break down complex sugars derived from glycoproteins in the lysosome, causes progressive lysosomal accumulation of mannose-rich oligosaccharides in all tissues, resulting in impaired cellular function and apoptosis (Figure 2). Complete absence of functionality in this enzyme leads to death during early childhood due to deterioration of the central nervous system. Enzymes with low residual activity lead to a milder form of the disease, with symptoms such as impaired hearing, cognitive impairment, susceptibility to bacterial infections, and skeletal deformities. The course of the disease is progressive. Depending on the severity of the disease,<unk>  has been classified into three proposed subtypes, based on severity and age of onset. * Type 1: A mild form, recognized after age ten years, with absence of skeletal abnormalities, muscle problems (myopathy), and slow progression * Type 2: A moderate form, recognized before age ten years, with presence of skeletal abnormalities, myopathy, and slow progression. This is the most common form * Type 3: A severe form, leading to early death from progressive central nervous system involvement However, given the variety of mutations that have been documented, and the broad range and severity of symptoms, the disease is considered clinically as a continuum.
Alpha-mannosidosis
Beta-mannosidosis
Galactosialidosis
Aspartylglucosaminuria
Essential fructosuria
Alkaptonuria
Hawkinsinuria
Glycosuria