出典(authority):フリー百科事典『ウィキペディア(Wikipedia)』「2019/06/19 10:36:29」(JST)
バーター症候群 | |
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Scheme of renal tubule and its vascular supply. | |
分類および外部参照情報 | |
診療科・ 学術分野 | 内分泌学 |
ICD-10 | E26.8 |
ICD-9-CM | 255.13 |
OMIM | 601678 241200 607364 602522 |
DiseasesDB | 1254 |
eMedicine | med/213 ped/210 |
MeSH | D001477 |
バーター症候群(バーターしょうこうぐん、Bartter syndrome)は、ヘンレ係蹄の太い上行脚(TAL)の機能不全を特徴とする症候群[1]。
本症候群は、フレデリック・バーターらによって提唱された疾患概念である。1960年に最初の報告がなされ、1962年にはより多くの症例に基づく報告がなされた[2][3][4][5]。
本症候群は、腎臓のTALの機能不全を主体とする続発性アルドステロン症の一つであり、レニン・アンギオテンシン・アルドステロン(RAA)系の亢進にもかかわらず、血圧が正常ないし軽度高値程度に留まっていることが特徴である。機能不全はいずれも遺伝的素因によるものと考えられており、その機序に応じてI〜V型に分類される[6]。
遠位尿細管の緻密斑では、原尿中のCl-の濃度が低いほど糸球体傍細胞でのレニン分泌を亢進させるように、レニン・アンギオテンシン・アルドステロン(RAA)系を調節している。その際に、緻密斑細胞が原尿中のCl-の濃度を感知する上で、Na+-K+-2Cl-共輸送体が重要な役割をはたしていると考えられている。しかし、例えば本症候群I型によってNKCC2が機能不全に陥ると、原尿中のCl-の濃度を緻密斑が感知できなくなるため、原尿中のCl-の濃度が低いと誤認識を起こし、糸球体傍細胞でのレニン分泌が異常に亢進する。その結果、RAA系が過剰に賦活されアルドステロンの分泌を異常に促し、続発性アルドステロン症を起こす。
続発性アルドステロン症は低カリウム血症と代謝性アルカローシスを起こす。続発性アルドステロン症によって起こされた低カリウム血症は腎臓で合成されるプロスタグランジンの産成を異常に促進し、過剰に産成されたプロスタグランジンはRAA系を更に賦活すると言う悪循環ができる。一方、レニンの昇圧作用とプロスタグランジンの降圧作用が相殺されて、血圧は正常に保たれる。
本症においては、その機序からしても、ループ利尿薬の過剰投与時と同様の臨床症状・検査所見が認められる。
低カリウム血症による筋力低下、四肢麻痺、尿濃縮力低下による多尿等を来たし、腎不全に至る。
本症においては、乳児期から低カリウム血症を発症し、成人までに1/3が末期腎不全に至る。
先天異常なので対症療法を行う。低カリウム血症に対してはカリウムを補給する。低クロール血症に対してはKClの経口投与で補給する。アルドステロン症に対しては、アルドステロン受容体拮抗薬スピロノラクトンを投与する。プロスタグランジンの過剰産生に対しては、プロスタグランジン産成阻害薬のインドメサシン等を投与する。
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この項目は、医学に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています(プロジェクト:医学/Portal:医学と医療)。 |
Bartter syndrome | |
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Scheme of renal tubule and its vascular supply. | |
Specialty | Endocrinology |
Bartter syndrome is a rare inherited disease characterised by a defect in the thick ascending limb of the loop of Henle, which results in low potassium levels (hypokalemia),[1] increased blood pH (alkalosis), and normal to low blood pressure. There are two types of Bartter syndrome: neonatal and classic. A closely associated disorder, Gitelman syndrome, is milder than both subtypes of Bartter syndrome.
In 90% of cases, neonatal Bartter syndrome is seen between 24 and 30 weeks of gestation with excess amniotic fluid (polyhydramnios). After birth, the infant is seen to urinate and drink excessively (polyuria, and polydipsia, respectively). Life-threatening dehydration may result if the infant does not receive adequate fluids. About 85% of infants dispose of excess amounts of calcium in the urine (hypercalciuria) and kidneys (nephrocalcinosis), which may lead to kidney stones. In rare occasions, the infant may progress to renal failure.
Patients with classic Bartter syndrome may have symptoms in the first two years of life, but they are usually diagnosed at school age or later. Like infants with the neonatal subtype, patients with classic Bartter syndrome also have polyuria, polydipsia, and a tendency to dehydration, but normal or just
slightly increased urinary calcium excretion without the tendency to develop kidney stones. These patients also have vomiting and growth retardation. Kidney function is also normal if the disease is treated,[2] but occasionally patients proceed to end-stage kidney failure. Bartter syndrome consists of low levels of potassium in the blood, alkalosis, normal to low blood pressures, and elevated plasma renin and aldosterone. Numerous causes of this syndrome probably exist. Diagnostic pointers include high urinary potassium and chloride despite low serum values, increased plasma renin, hyperplasia of the juxtaglomerular apparatus on kidney biopsy, and careful exclusion of diuretic abuse. Excess production of prostaglandins by the kidneys is often found. Magnesium wasting may also occur. Homozygous patients suffer from severe hypercalciuria and nephrocalcinosis.[3]
Bartter syndrome is caused by mutations of genes encoding proteins that transport ions across renal cells in the thick ascending limb of the nephron also called as the ascending loop of Henle.[2] Specifically, mutations directly or indirectly involving the Na-K-2Cl cotransporter are key. The Na-K-2Cl cotransporter is involved in electroneutral transport of one sodium, one potassium, and two chloride ions across the apical membrane of the tubule. The basolateral calcium-sensing receptor has the ability to downregulate the activity of this transporter upon activation. Once transported into the tubule cells, sodium ions are actively transported across the basolateral membrane by Na+/K+-ATPases, and chloride ions pass by facilitated diffusion through basolateral chloride channels. Potassium, however, is able to diffuse back into the tubule lumen through apical potassium channels, returning a net positive charge to the lumen and establishing a positive voltage between the lumen and interstitial space. This charge gradient is obligatory for the paracellular reabsorption of both calcium and magnesium ions.
Proper function of all of these transporters is necessary for normal ion reabsorption along the thick ascending limb, and loss of any component can result in functional inactivation of the system as a whole and lead to the presentation of Bartter syndrome. Loss of function of this reabsorption system results in decreased sodium, potassium, and chloride reabsorption in the thick ascending limb, as well as abolishment of the lumen-positive voltage, resulting in decreased calcium and magnesium reabsorption. Loss of reabsorption of sodium here also has the undesired effect of abolishing the hypertonicity of the renal medulla, severely impairing the ability to reabsorb water later in the distal nephron and collecting duct system, leading to significant diuresis and the potential for volume depletion. Finally, increased sodium load to the distal nephron elicits compensatory reabsorption mechanisms, albeit at the expense of potassium by excretion by principal cells and resulting hypokalemia. This increased potassium excretion is partially compensated by α-intercalated cells at the expense of hydrogen ions, leading to metabolic alkalosis.
Bartter and Gitelman syndromes can be divided into different subtypes based on the genes involved:[4]
Name | Bartter type | Associated gene mutations | Defect |
neonatal Bartter's syndrome | type 1 | SLC12A1 (NKCC2) | Na-K-2Cl symporter |
neonatal Bartter's syndrome | type 2 | ROMK/KCNJ1 | thick ascending limb K+ channel |
classic Bartter's syndrome | type 3 | CLCNKB | Cl− channel |
Bartter's syndrome with sensorineural deafness | type 4 | BSND[5] | Cl− channel accessory subunit |
Bartter's syndrome associated with autosomal dominant hypocalcemia | type 5 | CASR[6] | activating mutation of the calcium-sensing receptor |
Gitelman's syndrome | - | SLC12A3 (NCCT) | Sodium-chloride symporter |
People suffering from Bartter syndrome present symptoms that are identical to those of patients who are on loop diuretics like furosemide, given that the loop diuretics target the exact transport protein that is defective in the syndrome (at least for type 1 Bartter syndrome). The other subtypes of the syndrome involve mutations in other transporters that result in functional loss of the target transporter.
The clinical findings characteristic of Bartter syndrome are hypokalemia, metabolic alkalosis, and normal to low blood pressure. These findings may also be caused by:
Patients with Bartter syndrome may also have elevated renin and aldosterone levels.[7]
Prenatal Bartter syndrome can be associated with polyhydramnios.[8]
While patients should be encouraged to include liberal amounts of sodium[citation needed] and potassium in their diet, potassium supplements are usually required, and spironolactone is also used to reduce potassium loss.[1]
Nonsteroidal anti-inflammatory drugs (NSAIDs) can be used as well, and are particularly helpful in patients with neonatal Bartter syndrome.
Angiotensin-converting enzyme (ACE) inhibitors can also be used.
The limited prognostic information available suggests that early diagnosis and appropriate treatment of infants and young children with classic Bartter Syndrome may improve growth and perhaps intellectual development. On the other hand, sustained hypokalemia and hyperreninemia can cause progressive tubulointerstitial nephritis, resulting in end-stage kidney disease (kidney failure). With early treatment of the electrolyte imbalances, the prognosis for patients with classic Bartter Syndrome is good.
The condition is named after Dr. Frederic Bartter, who, along with Dr. Pacita Pronove, first described it in 1960 and in more patients in 1962.[7][9][10][11]
However, Bartter syndrome is also characterized by high renin, high aldosterone, hypercalciuria, and an abnormal Na+-K+-2Cl− transporter in the thick ascending limb of the loop of Henle, whereas Gitelman syndrome causes hypocalciuria and is due to an abnormal thiazide-sensitive transporter in the distal segment.
Pseudo-Bartter’s syndrome is a syndrome of similar presentation as Bartter syndrome but without any of its characteristic genetic defects. Pseudo-Bartter’s syndrome has been seen in cystic fibrosis,[13] as well as in excessive use of laxatives.[14]
Classification | D
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Diseases of the endocrine system (E00–E35, 240–259) | |||||||||||||||||||||||||||||||||
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Diseases of the urinary system (N00–N39, 580–599) | |||||||||||||||||||||||||||||||||
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Kidney disease |
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Urinary tract |
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Diseases of ion channels | |||||
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Calcium channel |
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Sodium channel |
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Potassium channel |
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Chloride channel |
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TRP channel |
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Connexin |
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Porin |
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See also: ion channels |
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リンク元 | 「バーター症候群」「ガルナー症候群」 |
拡張検索 | 「Schwartz-Bartter syndrome」「factitious-Bartter syndrome」「pseudo-Bartter syndrome」 |
関連記事 | 「syndrome」 |
Location | Phenotype | Phenotype | Gene/Locus | Gene/Locus | ||||
MIM number | MIM number | |||||||
1 | 15q21.1 | [[1]] | Bartter syndrome, type 1 | 601678 | [[2]] | SLC12A1 | 600839 | [[3]] |
2 | 11q24.3 | [[4]] | Bartter syndrome, type 2 | 241200 | [[5]] | KCNJ1 | 600359 | [[6]] |
3 | 1p36.13 | [[7]] | Bartter syndrome, type 3 | 607364 | [[8]] | CLCNKB | 602023 | [[9]] |
4A | 1p36.13 | [[10]] | Bartter syndrome, type 4, digenic | 602522 | [[11]] | CLCNKB | ||
1p32.3 | [[12]] | Bartter syndrome, type 4a | BSND | 606412 | [[13]] | |||
Sensorineural deafness with mild renal dysfunction | ||||||||
4B | 1p36.13 | [[14]] | Bartter syndrome, type 4b, digenic | 613090 | [[15]] | CLCNKA | 602024 | [[16]] |
カリウム | 血圧 | レニン | アルドステロン | pH | その他 | |
Bartter症候群 | 低カリウム血症 | 正常 | 高値 | 高値 | 代謝性アルカローシス | |
原発性アルドステロン症 | 低カリウム血症 | 高血圧 | 低値 | 高値 | 代謝性アルカローシス | |
二次アルドステロン症 | 低カリウム血症 | 高血圧 | 高値 | 高値 | 代謝性アルカローシス | |
尿細管性アシドーシス | 低カリウム血症 | 代謝性アシドーシス | ||||
甲状腺機能亢進症 | 低カリウム血症 | |||||
Liddle症候群 | 低カリウム血症 | 高血圧 | 低値 | 低値 | ACTH高値 |
バーター症候群 | ギテルマン症候群 | |
異常部位 | ヘンレの太い上行脚 | 遠位曲尿細管 |
共通点病態 | 二次性アルドステロン症 | |
低カリウム性アルカローシス | ||
RAA系亢進 | ||
正常血圧 | ||
診断時年齢 | 6歳以下 | 学童~成人 |
成長障害 | 多い | 無し~少ない |
羊水過多 | 44% | 0% |
テタニー | 少ない | 多い |
尿中カルシウム | 正常~増加 | 減少 |
低マグネシウム血症 | 40% | 100% |
低ナトリウム血症 | 多い | 少ない |
遠位尿細管Cl再吸収 | 高度低下 | 軽度~中等度低下 |
多飲・多尿・脱水 | 中等度~高度 | 無~中等度 |
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