<unk> s <unk> s; ) are a group of over 70 rare inherited metabolic disorders that result from defects in<unk>  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 due to a mutation, the large molecules accumulate within the cell, eventually killing it.<unk>  storage disorders are caused by<unk>  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,<unk> s 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, but 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 use. Lysosomes break down this unwanted matter by enzymes, highly specialized proteins essential for survival.<unk>  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 disorders, individuals inherit<unk> s 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<unk>  disorders originate from an abnormal accumulation of substances inside the lysosome.<unk> s affect mostly children and they often die at a young age, many within a few months or years of birth.
Lysosomal storage disease
Glycogen storage disease
Neutral lipid storage disease
Lipid storage disorder
Creatine transporter defect
D-bifunctional protein deficiency
Trinucleotide repeat disorder
Hyaluronidase deficiency