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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hyperammonemia is mainly found in hepatic encephalopathy and in genetic defects of the urea cycle or other pathways of the intermediary metabolism. Clinically a difference has to be made between chronic moderate hyperammonemia and acutely increased concentrations. Pathogenetic mechanisms of ammonia toxicity to the brain are partly unraveled. In some animal models confounding variables, such as the reduced intake of food and amino acid imbalance due to liver insufficiency, do not allow to establish unequivocal causal relationships between the ammonia concentration and measured effects. In chronic moderate hyperammonemia an increased flux through the serotonin pathway is a key factor. It is caused by an increased transport of large neutral amino acids (including tryptophan) through the blood-brain barrier, accentuated by the imbalance of plasma amino acids in hepatic insufficiency. It is stimulated by D- or L-glutamine. Evidence is presented showing that a functioning gamma-glutamyl cycle (glutathione formation) is a prerequisite. In acute hyperammonemia involvement of NMDA receptors, glutamate, NO and cGMP plays an additional role. In hyperammonemic crises the increased cerebral blood flow leads to brain edema; factors discussed here are increased osmolytes in astrocytes and serotoninergic activity. Recent data indicate that axonal development is affected by ammonia and can be normalized in vitro by creatine supplementation in developing mixed brain cell aggregate cultures, thus reviving the old hypothesis of the impact of hyperammonemia on energy metabolism in the developing brain that could cause mental retardation.
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PMID:Mechanisms of hyperammonemia. 1224 Oct 9

Helicobacter pylori (formerly Campylobacter pylori ) was identified in 1982 by researchers from Australia as a pathogenic factor in peptic ulcer disease. Due to the few studies on H. pylori infection conducted in the population of persons with intellectual disability it was decided to conduct a clinical study in Israel. The purpose of the study was to determine the occurrence of H. pylori infection in persons who presented with severe dyspeptic symptoms and to monitor clinically the effect of treatment. The Division for Mental Retardation in Israel provides service to 6,022 persons in 53 residential care centers and 1 in central Israel was selected for this pilot study. The study has been performed since 1999 and each patient who came to the medical clinic of the institution with severe dyspeptic symptoms was examined clinically and a blood specimen drawn for IgG antibodies to H. pylori (ELISA, Pharmatop Millenia). In case of positive serology, triple drug treatment (amoxycillin, metronidazole, and pantoprazole or omeprazole) was initiated for 1 week. Since 1999 a total of 43 persons (total population in care was 224) had severe dyspeptic symptoms and 42 persons (98%, 26 males, 16 females, mean age 45 years, mean institutionalization 20 years) had Helicobacter infection. All patients were treated for 1 week, but six patients received an extra month of omeprazole due to persistent symptoms. At follow-up, clinically all patients had improvement and only seven still had minor complaints (83% treatment success). Persons with developmental disability, intellectual disability, or mental retardation in residential care presenting with severe dyspeptic symptoms had a high incidence of H. pylori infection. Therefore, we recommend serology or urea breath investigations in this population presenting with dyspeptic symptoms and triple drug treatment for 1 week in case of positive findings.
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PMID:Helicobacter pylori infection in persons with intellectual disability in residential care in Israel. 1280 82

Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive disorder caused by mutations in the neurotrophic tyrosine receptor kinase 1 (NTRK1) gene which encodes the receptor for nerve growth factor (NGF). We report the clinical course in three sibs with CIPA and proven NTRK1 gene mutations with a follow-up over a 25-year period in one of them. They had the characteristic clinical features of an abnormally high pain threshold, and mental retardation; in addition their clinical course was marked by the occurrence of early onset renal disease with recurrent microhematuria and proteinuria and frequent observations of increased serum creatinine and blood urea levels. Light microscopy study of a renal biopsy performed in one of them at age of 20 months showed focal glomerulosclerosis, interstitial fibrosis and tubular atrophy. This patient and his younger brother died because of renal failure at the age of 25 years and 14 years, respectively. The sister still alive showed renal impairment and deep venous thrombosis associated with lupus anticoagulant activity, decrease of circulating autoreactive CD5 (+) B lymphocytes and increased urinary levels of IgG and kappa and lambda light chains, suggesting a possible defect in regulation of B-lymphocyte function. In the light of the NGF-related molecular defect, the extraneurological tissue involvement in CIPA might in part reflect dysregulation of immune mechanisms which possibly brings about a chronic inflammatory response. This, in turn, could result in renal disease which should be mentioned among the life-threatening complications associated with this disorder.
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PMID:Congenital insensitivity to pain with Anhidrosis (NTRK1 mutation) and early onset renal disease: clinical report on three sibs with a 25-year follow-up in one of them. 1613 53

Arginase deficiency is an urea cycle disorder that generally presents with mental retardation and spasticity, yet uncommonly with episodes of hyperammonemia. A female adolescent with arginase deficiency developed hyperammonemic episodes temporally related to her menstrual cycle, which ceased upon adequate treatment with depot medroxy progesterone acetate. A similar case was previously reported. A catamenial trigger should be considered in adolescent female arginase-deficient patients with episodes of hyperammonemia.
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PMID:A patient with arginase deficiency and episodic hyperammonemia successfully treated with menses cessation. 1696

Argininosuccinicaciduria is a rare metabolic disorder of the urea cycle associated with the inability to excrete nitrogenous waste in the form of urea. Along with low serum arginine, hepatomegaly, and mental retardation, congenital trichorrhexis nodosa is a distinguishing feature of the disorder. We present a 3.5-year-old girl diagnosed with argininosuccinicaciduria who presented to the dermatology clinic with hair thinning and loss since birth. Microscopic evaluation revealed nodular swellings on the hair shafts and frayed cortical fibers consistent with the diagnosis of trichorrhexis nodosa occurring in the setting of argininosuccinicaciduria.
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PMID:Trichorrhexis nodosa secondary to argininosuccinicaciduria. 1730 Jun 44

Acute hyperammonemia (HA) causes cerebral edema and brain damage in children with urea cycle disorders (UCDs) and in patients in acute liver failure. Chronic HA is associated with developmental delay and mental retardation in children with UCDs, and with neuropsychiatric symptoms in patients with chronic liver failure. Astrocytes are a major cellular target of hyperammonemic encephalopathy, and changes occurring in these cells are thought to be causally related to the brain edema of acute HA. To study the effect of HA on astrocytes in vivo, we crossed the Otc(spf) mouse, a mouse with the X-linked UCD ornithine transcarbamylase (OTC) deficiency, with the hGFAP-EGFP mouse, a mouse selectively expressing green fluorescent protein in astrocytes. We used FACS to purify astrocytes from the brains of hyperammonemic and healthy Otcspf/GFAP-EGFP mice. RNA isolated from these astrocytes was used in microarray expression analyses and qRT-PCR. When compared with healthy littermates, we observed a significant downregulation of the gap-junction channel connexin 43 (Cx43) the water channel aquaporin 4 (Aqp4) genes, and the astrocytic inward-rectifying potassium channel (Kir) genes Kir4.1 and Kir5.1 in hyperammonemic mice. Aqp4, Cx43, and Kir4.1/Kir5.1 are co-localized to astrocytic end-feet at the brain vasculature, where they regulate potassium and water transport. Since, NH4+ ions can permeate water and K+-channels, downregulation of these three channels may be a direct effect of elevated blood ammonia levels. Our results suggest that alterations in astrocyte-mediated water and potassium homeostasis in brain may be key to the development of the brain edema.
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PMID:Gene expression profiling of astrocytes from hyperammonemic mice reveals altered pathways for water and potassium homeostasis in vivo. 1818 79

l-Proline concentration is primarily related to the balance of enzymatic activities of proline dehydrogenase [proline oxidase (POX)] and Delta-1-pyrroline-5-carboxylate (P5C) reductase. As a result, P5C plays a pivotal role in maintaining the concentration of proline in body fluids and inborn errors of P5C metabolism lead to disturbance of proline metabolism. Several inborn errors of proline metabolism have been described. Hyperprolinemia type I (HPI) is a result of a deficiency in POX. The POX gene (PRODH) is located on chromosome 22 (22q11.2) and this region is deleted in velo-cardio-facial syndrome, a congenital malformation syndrome. In addition, this gene locus is related to susceptibility to schizophrenia. The other type of hyperprolinemia is HPII. It is caused by a deficiency in P5C dehydrogenase activity. Hypoprolinemia, on the other hand, is found in the recently described deficiency of P5C synthetase. This enzyme defect leads to hyperammonemia associated with hypoornithinemia, hypocitrullinemia, and hypoargininemia other than hypoprolinemia. Hyperhydroxyprolinemia is an autosomal recessive inheritance disorder caused by the deficiency of hydroxyproline oxidase. There are no symptoms and it is believed to be a benign metabolic disorder. The deficiency of ornithine aminotransferase causes transient hyperammonemia during early infancy due to deficiency of ornithine in the urea cycle. In later life, gyrate atrophy of the retina occurs due to hyperornithinemia, a paradoxical phenomenon. Finally, prolidase deficiency is a rare autosomal recessive hereditary disease. Prolidase catalyzes hydrolysis of dipeptide or oligopeptide with a C-terminal proline or hydroxyproline and its deficiency can cause mental retardation and severe skin ulcers.
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PMID:Inborn errors of proline metabolism. 1880 17

A 4-year old boy was referred for evaluation of renal failure, posterior urethral valve (PUV) and urinary tract infection. His parents added complaints of polyuria, polydipsia, enuresis, shortness of stature, and inappropriate obesity. Serum blood urea nitrogen and creatinine levels were 45 and 3.5 mg/dL, respectively. Urine culture was positive for Pseudomonas aeruginosa, and abdominal ultrasound revealed bilateral small kidneys. The patient's history included mild to moderate mental retardation and postaxial polydactyly of both lower limbs amputated two years ago. The combination of mental retardation, obesity, postaxial polydactyly, and bilateral renal hypoplasia were compatible with the diagnosis Bardet-Biedl syndrome (BBS). The combination of PUV and BBS is a rare condition that caused this early onset of renal failure and inappropriate obesity guided us to the diagnosis.
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PMID:Bardet-biedl syndrome in a child with chronic kidney disease. 1941 50

Congenital portosystemic shunts (PSS) are rare vascular anomalies with different gross anatomy. Persistent patent ductus venosus (PDV) represents an uncommon cause of intrahepatic PSS. The diagnosis of this condition may not be obvious because of its wide spectrum of clinical manifestations, ranging from asymptomatic to life-threatening disease. We report the case of three boys with neuropsychological symptoms associated with mild fasting hyperammonemia. An oral protein load allowed the detection of a detoxication defect due to PSS related to PDV. This simple procedure can be worthwhile of attention in patients with mental retardation, behavior disturbances, and learning difficulties after exclusion of common causes of inherited hyperammonemia, namely, urea cycle disorders, organic acidemias, and fatty acid oxidation defects.
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PMID:Remittent hyperammonemia in congenital portosystemic shunt. 1961 12

Inherited urea cycle disorders represent one of the most common groups of inborn errors of metabolism. Late-onset urea cycle disorders caused by partial enzyme deficiencies may present with unexpected clinical phenotypes. We report 9 patients followed up in our hospital presenting late-onset urea cycle disorders who initially manifested neuropsychiatric/neurodevelopmental symptoms (the most prevalent neuropsychiatric/neurodevelopmental diagnoses were mental retardation, attention-deficit hyperactivity disorder [ADHD], language disorder, and delirium). Generally, these clinical pictures did not benefit from pharmacological treatment. Conversely, dietary treatment improved the symptoms. Regarding biochemical data, 2 patients showed normal ammonium but high glutamine levels. This study highlights the fact that neuropsychiatric/neurodevelopmental findings are common among the initial symptomatology of late-onset urea cycle disorders. The authors recommend that unexplained or nonresponsive neuropsychiatric/neurodevelopmental symptoms appearing during childhood or adolescence be followed by a study of ammonia and amino acid plasmatic levels to rule out a urea cycle disorder.
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PMID:Neuropsychiatric manifestations in late-onset urea cycle disorder patients. 1968 5


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