Eosinophilia-myalgia syndrome | |
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Other names | EMS |
Specialty | Rheumatology ![]() |
Eosinophilia–myalgia syndrome is a rare, sometimes fatal neurological condition linked to the ingestion of the dietary supplement L-tryptophan. [1] [2] The risk of developing EMS increases with larger doses of tryptophan and increasing age. [3] Some research suggests that certain genetic polymorphisms may be related to the development of EMS. [4] The presence of eosinophilia is a core feature of EMS, along with unusually severe myalgia (muscle pain). [5] [6] [7]
The initial, acute phase of EMS, which last for three to six months, presents as trouble with breathing and muscle problems, including soreness and spasm, but which may also be intense. Muscle weakness is not a feature of this phase, but some people experience muscle stiffness. Additional features can include cough, fever, fatigue, joint pain, edema, and numbness or tingling, usually in the limbs, hands and feet. [8]
The chronic phase follows the acute phase. Eosinophilic fasciitis may develop, primarily in the limbs. CNS signs may appear, including numbness, increased sensation, muscle weakness, and sometimes cardiac or digestive dysfunction. Fatigue is present to some degree, while the muscle pain (which may be extremely intense) and dyspnea continue in this phase. [8]
Subsequent[ clarification needed ] epidemiological studies suggested that EMS was linked to specific batches of L-tryptophan supplied by a single large Japanese manufacturer, Showa Denko. [9] [10] [11] [12] It eventually became clear that recent batches of Showa Denko's L-tryptophan were contaminated by trace impurities, which were subsequently thought to be responsible for the 1989 EMS outbreak. The L-tryptophan was produced by a bacterium grown in open vats in a Showa Denko fertilizer factory. [9] [13] [14] While a total of 63 trace contaminants were eventually identified, only six of them could be associated with EMS. [3] [15] The compound EBT (1,1'-ethylidene-bis-L-tryptophan, also known as "Peak E") was the only contaminant identifiable by initial analysis, but further analysis revealed PAA (3-(phenylamino)-L-alanine, also known as "UV-5"), and peak 200 (2[3-indolyl-methyl]-L-tryptophan). Two of the remaining uncharacterized peaks associated with EMS were later determined to be 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo-[2,3-b]-indole-2-carboxylic acid (peak C) and 2-(2-hydroxy indoline)-tryptophan (peak FF). These were characterized using accurate mass LC–MS, LC–MS/MS and multistage mass spectrometry (MSn). [16] The last of the six contaminants (peak AAA/"UV-28", [17] being "the contaminant most significantly associated with EMS" [3] has been characterized as two related chain-isomers; peak AAA1 ((S)-2-amino-3-(2-((S,E)-7-methylnon-1-en-1-yl)-1H-indol-3-yl)propanoic acid, a condensation product between L-tryptophan and 7-methylnonanoic acid) and peak AAA2 ((S)-2-amino-3-(2-((E)-dec-1-en-1-yl)-1H-indol-3-yl)propanoic acid, a condensate between L-tryptophan and decanoic acid). [18] No consistent relationship has ever been firmly established between any specific trace impurity or impurities identified in these batches and the effects of EMS. While EBT in particular has been frequently implicated as the culprit, there is no statistically significant association between EBT levels and EMS. [3] Of the 63 trace contaminants, only the two AAA compounds displayed a statistically significant association with cases of EMS (with a p-value of 0.0014). [18]
As most research has focused on attempts to associate individual contaminants with EMS, there is a comparative lack of detailed research on other possible causal or contributing factors. Tryptophan itself has been implicated as a potentially major contributory factor in EMS. [19] While critics of this theory have argued that this hypothesis fails to explain the near-absent reports of EMS prior to and following the EMS outbreak, [20] this fails to take into account the sudden rapid increase in tryptophan's usage immediately prior to the 1989 outbreak, and ignores the strong influence of the EMS outbreak's legacy and the extended FDA ban on later usage of tryptophan. [19] Crucially, this also ignores the existence of a number of cases of EMS that developed both prior to and after the primary epidemic, including at least one case where the tryptophan was tested and found to lack the contaminants found in the contaminated lots of Showa Denko's tryptophan, as well as cases with other supplements inducing EMS, and even a case of EMS induced by excessive dietary L-tryptophan intake via overconsumption of cashew nuts. [21] [22] [23] [24] [9] [19] [25] [26] [27] [ excessive citations ] A major Canadian analysis located a number of patients that met the CDC criteria for EMS but had never been exposed to tryptophan, which "brings causal interpretations of earlier studies into question". [6] [28] Other studies have highlighted numerous major flaws in many of the epidemiological studies on the association of tryptophan with EMS, which cast serious doubt on the validity of their results. [29] [30] As the FDA concluded, "other brands of L-tryptophan, or L-tryptophan itself, regardless of the levels or presence of impurities, could not be eliminated as causal or contributing to the development of EMS". [9] Even animal studies have suggested that tryptophan itself "when ingested by susceptible individuals either alone or in combination with some other component in the product, results in the pathological features in EMS". [9] [31]
At the time of the outbreak, Showa Denko had recently made alterations to its manufacturing procedures that were thought to be linked to the possible origin of the contaminants detected in the affected lots of tryptophan. A key change was the reduction of the amount of activated charcoal used to purify each batch from >20 kg to 10 kg. [3] A portion of the contaminated batches had also bypassed another filtration step that used reverse-osmosis to remove certain impurities. [3] Additionally, the bacterial culture used to synthesize tryptophan was a strain of Bacillus amyloliquefaciens that had been genetically engineered to increase tryptophan production. Although the prior four generations of the genetically engineered strain had been used without incident, the fifth generation used for the contaminated batches was thought to be a possible source of the impurities that were detected. This has been used to argue that the genetic engineering itself was the primary cause of the contamination, a stance that was heavily criticized for overlooking the other known non-GMO causes of contamination, as well as for its use by anti-GMO activists as a way to threaten the development of biotechnology with false information. [32] The reduction in the amount of activated carbon used and the introduction of the fifth generation Bacillus amyloliquefaciens strain were both associated with the development of EMS, but due to the high overlap of these changes, the precise independent contribution of each change could not be determined (although the bypass of the reverse-osmosis filtration for certain lots was determined to be not significantly associated with the contaminated lots of tryptophan). [3] While Showa Denko claimed a purity of 99.6%, it was noted that "the quantities of the known EMS associated contaminants, EBT and PAA, were remarkably small, of the order of 0.01%, and could easily escape detection". [3]
The FDA loosened its restrictions on sales and marketing of tryptophan in February 2001, [9] but continued to limit the importation of tryptophan not intended for an exempted use until 2005. [25]
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Treatment is withdrawal of products containing L-tryptophan and the administration of glucocorticoids. Most patients recover fully, remain stable, or show slow recovery, but the disease is fatal in up to 5% of patients.[ citation needed ]
The first case of eosinophilia–myalgia syndrome was reported to the Centers for Disease Control and Prevention (CDC) in November 1989, although some cases had occurred as early as 2–3 years before this. [5] [21] [22] [23] [24] In total, more than 1,500 cases of EMS were reported to the CDC, as well as at least 37 EMS-associated deaths. After preliminary investigation revealed that the outbreak was linked to intake of tryptophan, the U.S. Food and Drug Administration (FDA) recalled tryptophan supplements in 1989 and banned most public sales in 1990, [9] [33] [34] with other countries following suit. This FDA restriction was loosened in 2001, and fully lifted in 2005. [35] [36] Since the initial ban on L-tryptophan, a normal metabolite of the compound in mammals, 5-hydroxtryptophan (5-HTP) has become a popular replacement dietary supplement. [37]
gamma-Hydroxybutyric acid (GHB), also known as 4-hydroxybutanoic acid is a naturally occurring neurotransmitter and a depressant drug. It is a precursor to GABA, glutamate, and glycine in certain brain areas. It acts on the GHB receptor and is a weak agonist at the GABAB receptor. GHB has been used in the medical setting as a general anesthetic and as treatment for cataplexy, narcolepsy, and alcoholism. The substance is also used illicitly for various reasons, including as a performance-enhancing drug, date rape drug, and as a recreational drug.
Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic beta carbon substituent. Tryptophan is also a precursor to the neurotransmitter serotonin, the hormone melatonin, and vitamin B3 (niacin). It is encoded by the codon UGG.
Coenzyme Q10 (CoQ10) also known as ubiquinone, is a naturally occurring biochemical cofactor (coenzyme) and an antioxidant produced by the human body. It can also be obtained from dietary sources, such as meat, fish, seed oils, vegetables, and dietary supplements. CoQ10 is found in many organisms, including animals and bacteria.
Myalgia or muscle pain is a painful sensation evolving from muscle tissue. It is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, especially when there has been no injury.
Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells and basophils, they also control mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood, after which they are terminally differentiated and do not multiply.
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 5×108/L (500/μL). Hypereosinophilia is an elevation in an individual's circulating blood eosinophil count above 1.5 × 109/L (i.e. 1,500/μL). The hypereosinophilic syndrome is a sustained elevation in this count above 1.5 × 109/L (i.e. 1,500/μL) that is also associated with evidence of eosinophil-based tissue injury.
Fibromyalgia is a medical syndrome which causes chronic widespread pain, accompanied by fatigue, waking unrefreshed, and cognitive symptoms. Other symptoms can include headaches, lower abdominal pain or cramps, and depression. People with fibromyalgia can also experience insomnia and a general hypersensitivity. The cause of fibromyalgia is unknown, but is believed to involve a combination of genetic and environmental factors. Environmental factors may include psychological stress, trauma, and certain infections. Since the pain appears to result from processes in the central nervous system, the condition is referred to as a "central sensitization syndrome".
Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis. Vasculitis is primarily caused by leukocyte migration and resultant damage. Although both occur in vasculitis, inflammation of veins (phlebitis) or arteries (arteritis) on their own are separate entities.
5-Hydroxytryptophan (5-HTP), also known as oxitriptan, is a naturally occurring amino acid and chemical precursor as well as a metabolic intermediate in the biosynthesis of the neurotransmitter serotonin.
Showa Denko K. K., founded in 1939 by the merger of Nihon Electrical Industries and Showa Fertilizers, both established by a Japanese entrepreneur Nobuteru Mori, is a Japanese chemical company producing chemical products and industrial materials.
A branched-chain amino acid (BCAA) is an amino acid having an aliphatic side-chain with a branch. Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine, and valine. Non-proteinogenic BCAAs include 2-aminoisobutyric acid and alloisoleucine.
Eosinophilic fasciitis, also known as Shulman's syndrome, is an inflammatory disease that affects the fascia, other connective tissues, surrounding muscles, blood vessels and nerves. Unlike other forms of fasciitis, eosinophilic fasciitis is typically self-limited and confined to the arms and legs, although it can require treatment with corticosteroids, and some cases are associated with aplastic anemia.
Toxic oil syndrome (TOS) or simply toxic syndrome is a musculoskeletal disease. A 1981 outbreak in Spain which affected about 25,600 people, with over 4,000 dying within a few months and a few thousand remaining disabled, is thought to have been caused by contaminated colza (rapeseed) oil. It was unique because of its size, the novelty of the clinical condition, and the complexity of its aetiology. Its first appearance was as a lung disease, with unusual features, though the symptoms initially resembled a lung infection. The disease appeared to be restricted to certain geographical localities, and several members of a family could be affected, even while their neighbours had no symptoms. Following the acute phase, a range of other chronic symptoms was apparent.
l-Kynurenine is a metabolite of the amino acid l-tryptophan used in the production of niacin.
Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas of thickened skin, stiffness, feeling tired, and poor blood flow to the fingers or toes with cold exposure. One form of the condition, known as CREST syndrome, classically results in calcium deposits, Raynaud's syndrome, esophageal problems, thickening of the skin of the fingers and toes, and areas of small, dilated blood vessels.
The kynurenine pathway is a metabolic pathway leading to the production of nicotinamide adenine dinucleotide (NAD+). Metabolites involved in the kynurenine pathway include tryptophan, kynurenine, kynurenic acid, xanthurenic acid, quinolinic acid, and 3-hydroxykynurenine. The kynurenine pathway is responsible for about 95% of total tryptophan catabolism. Disruption in the pathway is associated with certain genetic and psychiatric disorders.
Antisynthetase syndrome (ASS) is a multisystematic autoimmune disease associated with inflammatory myositis, interstitial lung disease, and antibodies directed against various synthetases of aminoacyl-transfer RNA. Other common symptoms include mechanic's hands, Raynaud's phenomenon, arthritis, and fever.
Eosinophilic myocarditis is inflammation in the heart muscle that is caused by the infiltration and destructive activity of a type of white blood cell, the eosinophil. Typically, the disorder is associated with hypereosinophilia, i.e. an eosinophil blood cell count greater than 1,500 per microliter. It is distinguished from non-eosinophilic myocarditis, which is heart inflammation caused by other types of white blood cells, i.e. lymphocytes and monocytes, as well as the respective descendants of these cells, NK cells and macrophages. This distinction is important because the eosinophil-based disorder is due to a particular set of underlying diseases and its preferred treatments differ from those for non-eosinophilic myocarditis.
Kelly J. Henning is an epidemiologist and medical doctor currently leading the public health program of Bloomberg Philanthropies. She has led the program since it began in 2007. She was the first person to serve as director of epidemiology for the New York City Department of Health and Mental Hygiene. Henning said of working in public health "I have the opportunity to help improve the health and lives of millions of people. That's what really speaks to me."
Benign acute childhood myositis (BACM) is a syndrome characterized by muscle weakness and pain in the lower limbs that develop in children after a recent viral illness. It is transient with a spontaneous clinical resolution within 1 week.