Gaucher's disease or Gaucher disease (/ɡoʊˈʃeɪ/) (GD) is a genetic disorder in which glucocerebroside (a sphingolipid, also known as glucosylceramide) accumulates in cells and certain organs. The disorder is characterized by bruising, fatigue, anemia, low blood platelet count and enlargement of the liver and spleen, and is caused by a hereditary deficiency of the enzyme glucocerebrosidase (also known as glucosylceramidase), which acts on glucocerebroside. When the enzyme is defective, glucocerebroside accumulates, particularly in white blood cells and especially in macrophages (mononuclear leukocytes). Glucocerebroside can collect in the spleen, liver, kidneys, lungs, brain, and bone marrow. Manifestations may include enlarged spleen and liver, liver malfunction, skeletal disorders or bone lesions that may be painful, severe neurological complications, swelling of lymph nodes and (occasionally) adjacent joints, distended abdomen, a brownish tint to the skin, anemia, low blood platelet count, and yellow fatty deposits on the white of the eye (sclera). Persons seriously affected may also be more susceptible to infection. Some forms of Gaucher's disease may be treated with enzyme replacement therapy. The disease is caused by a recessive mutation in the GBA gene located on chromosome 1 and affects both males and females. About one in 100 people in the United States are carriers of the most common type of Gaucher disease. The carrier rate among Ashkenazi Jews is 8.9% while the birth incidence is one in 450. Gaucher's disease is the most common of the lysosomal storage diseases.It is a form of sphingolipidosis (a subgroup of lysosomal storage diseases), as it involves dysfunctional metabolism of sphingolipids. The disease is named after the French physician Philippe Gaucher, who originally described it in 1882.

Classification Gaucher's disease (GD) has three common clinical subtypes. GD type I (non-neuropathic) is the most common form of the disease, occurring in about one in 40,000 live births. It occurs most often among persons of Ashkenazi Jewish heritage. Symptoms may begin early in life or in adulthood and include enlarged liver and grossly enlarged spleen (together hepatosplenomegaly); the spleen can rupture and cause additional complications. Skeletal weakness and bone disease may be extensive. Spleen enlargement and bone marrow replacement cause anemia, thrombocytopenia, and leukopenia. The brain is not affected pathologically, but lung and, rarely, kidney impairment may occur. Patients in this group usually bruise easily (due to low levels of platelets) and experience fatigue due to low numbers of red blood cells. Depending on disease onset and severity, type I patients may live well into adulthood. The range and severity of symptoms can vary dramatically between patients. GD type II (acute infantile neuropathic) typically begins within 6 months of birth and has an incidence rate around one 1 in 100,000 live births. Symptoms include an enlarged liver and spleen, extensive and progressive brain damage, eye movement disorders, spasticity, seizures, limb rigidity, and a poor ability to suck and swallow. Affected children usually die by age two. GD type III (chronic neuropathic) can begin at any time in childhood or even in adulthood, and occurs in about one in 100,000 live births. It is characterized by slowly progressive, but milder neurologic symptoms compared to the acute or type II version. Major symptoms include an enlarged spleen and/or liver, seizures, poor coordination, skeletal irregularities, eye movement disorders, blood disorders including anemia, and respiratory problems. Patients often live into their early teen years and adulthood. These subtypes have come under some criticism for not taking account of the full spectrum of observable symptoms (the phenotypes). Also, compound heterozygous variations occur which considerably increase the complexity of predicting disease course. Signs and symptoms Painless hepatomegaly and splenomegaly: the size of the spleen can be 1500-3000 ml, as opposed to the normal size of 50-200 ml. Splenomegaly may decrease the affected individual's capacity for eating by exerting pressure on the stomach. While painless, enlargement of spleen increases the risk of splenic rupture. Hypersplenism and pancytopenia, the rapid and premature destruction of blood cells, leads to anemia, neutropenia, leukopenia, and thrombocytopenia (with an increased risk of infection and bleeding). Cirrhosis of the liver is rare. Severe pain associated with joints and bones occurs, frequently presenting in hips and knees. Neurological symptoms occur only in some types of Gaucher's (see below): Type I: impaired olfaction and cognition Type II: serious convulsions, hypertonia, mental retardation, and apnea Type III: muscle twitches known as myoclonus, convulsions, dementia, and ocular muscle apraxia Parkinson's disease is recognised as being more common in Gaucher's disease patients and their heterozygous carrier relatives. Osteoporosis: 75% of patients develop visible bony abnormalities due to the accumulated glucosylceramide. A deformity of the distal femur in the shape of an Erlenmeyer flask is commonly described (aseptic necrosis of the femur joint). Yellowish-brown skin pigmentation Pathophysiology The disease is caused by a defect in housekeeping gene for lysosomal glucocerebrosidase (also known as beta-glucosidase, EC, PDB: 1OGS​) on the first chromosome (1q22). The enzyme is a 55.6-kilodalton, 497-amino acid-long protein that catalyses the breakdown of glucosylceramide, a cell membrane constituent of red and white blood cells. The macrophages that clear these cells are unable to eliminate the waste product, which accumulates in fibrils, and turn into 'Gaucher cells', which appear on light microscopy to resemble crumpled-up paper. In the brain (type II and III), glucosylceramidase accumulates due to the turnover of complex lipids during brain development and the formation of the myelin sheath of nerves. Different mutations in the GBA (beta-glucosidase) gene determine the remaining activity of the enzyme, and, to a large extent, the phenotype. Heterozygotes for particular acid beta-glucosidase mutations carry about a five-fold risk of developing Parkinson's disease, making this the most common known genetic risk factor for Parkinson's. Cancer risk may be increased, particularly myeloma. This is thought to be due to accumulation of glucosylceramide and complex glycosphingolipids. Diagnosis Gaucher disease is suggested based on the overall clinical picture. Initial laboratory testing may include enzyme testing. As a result, lower than 15% of mean normal activity is considered to be diagnostic. Decreased enzyme levels will often be confirmed by genetic testing. Numerous different mutations occur; sequencing of the beta-glucosidase gene is sometimes necessary to confirm the diagnosis. Prenatal diagnosis is available, and is useful when a known genetic risk factor is present. A diagnosis can also be implied by biochemical abnormalities such as high alkaline phosphatase, angiotensin-converting enzyme, and immunoglobulin levels, or by cell analysis showing crinkled paper cytoplasm and glycolipid-laden macrophages. Some lysosomal enzymes are elevated, including tartrate-resistant acid phosphatase, hexosaminidase, and a human chitinase, chitotriosidase. This latter enzyme has proved to be very useful for monitoring Gaucher's disease activity in response to treatment, and may reflect the severity of the disease

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