Lysosomal storage disease
What is Lysosomal storage disease?
Lysosomal storage diseases (LSDs; ) are a group of approximately 50 rare inherited metabolic disorders that result from defects in lysosomal function. Lysosomes are sacs of enzymes within cells that digest large molecules and pass the fragments on to other parts of the cell for recycling. This process requires several critical enzymes. If one of these enzymes is defective, because of a mutation, the large molecules accumulate within the cell, eventually killing it.
Lysosomal storage disorders are caused by lysosomal dysfunction usually as a consequence of deficiency of a single enzyme required for the metabolism of lipids, glycoproteins (sugar containing proteins) or so-called mucopolysaccharides. Individually, LSDs occur with incidences of less than 1:100,000; however, as a group the incidence is about 1:5,000 - 1:10,000. Most of these disorders are autosomal recessively inherited such as Niemann-Pick disease, type C, however a few are X-linked recessively inherited, such as Fabry disease and Hunter syndrome (MPS II).
The lysosome is commonly referred to as the cell’s recycling center because it processes unwanted material into substances that the cell can utilize. Lysosomes break down this unwanted matter via enzymes, highly specialized proteins essential for survival. Lysosomal disorders are usually triggered when a particular enzyme exists in too small an amount or is missing altogether. When this happens, substances accumulate in the cell. In other words, when the lysosome does not function normally, excess products destined for breakdown and recycling are stored in the cell.
Like other genetic diseases, individuals inherit lysosomal storage diseases from their parents. Although each disorder results from different gene mutations that translate into a deficiency in enzyme activity, they all share a common biochemical characteristic – all lysosomal disorders originate from an abnormal accumulation of substances inside the lysosome.
Lysosomal storage diseases affect mostly children and they often die at a young and unpredictable age, many within a few months or years of birth. Many other children die of this disease following years of suffering from various symptoms of their particular disorder.