Mental retardation

Phenylpyruvic acid can cause mental retardation m infants who are deficient m the enzymes necessary to convert l phenylalanine to l tyrosine This disorder is called phenylketonuria, or PKU disease PKU disease can be detected by a simple test rou tmely administered to newborns It cannot be cured but is controlled by restricting the dietary intake of l phenylalanine In practice this means avoiding foods such as meat that are rich m l phenylalanine... 

In the case of hyperphenylalaninaemia, which occurs ia phenylketonuria because of a congenital absence of phenylalanine hydroxylase, the observed phenylalanine inhibition of proteia synthesis may result from competition between T.-phenylalanine and L-methionine for methionyl-/RNA. Patients sufferiag from maple symp urine disease, an inborn lack of branched chain oxo acid decarboxylase, are mentally retarded unless the condition is treated early enough. It is possible that the high level of branched-chain amino acids inhibits uptake of L-tryptophan and L-tyrosiae iato the brain. Brain iajury of mice within ten days after thek bkth was reported as a result of hypodermic kijections of monosodium glutamate (MSG) (0.5—4 g/kg). However, the FDA concluded that MSG is a safe kigredient, because mice are bom with underdeveloped brains regardless of MSG kijections (106). 

Lead is a heavy metal that remains in die bloodstream, causing mental retardation in children. It is believed that 3 X 10 7gofPbinl.00mL of blood is a health hazard. For this amount of lead... 

Cytomegalovirus (CMV) is a herpesvirus, which causes an inapparent infection in immunocompetent persons. Worldwide, approximately 40% of people are infected with CMV. In immunocompromised patients, transplant recipients and neonates, CMV can cause serious and potentially lethal disease manifestations like pneumonia, retinitis and blindness, hepatitis, infections of the digestive tract, deafness or mental retardation. 

Heriditary lysosomal storage disorder with an heterer-ogeneous clinical presentation including mental retardation and skeletal changes. The disease is caused by... 

VLDL receptor Loss-of-function (familial, autosomal recessive) Autosomal recessive cerebellar hypoplasia (ataxia, mental retardation)... 

CMV, a virus of the herpes family, isa common viral infection. Healthy individuals may beoome infected yet have no symptoms. However, immunocompromised patients (such as those with HIV or cancer) may have the infection. Symptoms include malaise, fever, pneumonia, and super infection. Infants may acquire the virus from the mother while in the uterus, resulting in learning disabilities and mental retardation. CM V can infect the eye, causing retinitis. Symptoms of CMV retinitis are blurred vision and decreased visual acuity. Visual impairment is irreversible and can lead to blindness if untreated. 

Potassium iodide is added as a nutrient to prevent goiter, a thyroid problem caused by lack of iodine, and to prevent a form of mental retardation associated with iodine deficiency. A project started by the Michigan State Medical Society in 1924 promoted the addition of iodine to table salt, and by the mid-1950s three-quarters of U.S. households used only iodized salt. Potassium iodide makes up 0.06 percent to 0.01 percent of table salt by weight. Sometimes cuprous iodide—iodide of copper—is used instead as the source of iodine. 

Tay-Sachs disease Hexosaminidase A Cer—Gic—Gal(NeuAc)-i-GalNAc GM2Gangiioside Mental retardation, blindness, muscular weakness. 

Metachromatic ieukodystrophy Aryisuifatase A Cgp—Gsl—j-OS03 3-Sulfogalactosylceramide Mental retardation and psychologic disturbances in adults demyelination. 

Krabbe s disease P-Gaiactosidase Cer-i-Gai Gaiactosyiceramide Mental retardation myelin almost absent. 

Gaucher s disease P-Giucosidase Cer-i-Gic Giucosyiceramide Enlarged liver and spleen, erosion of long bones, mental retardation in infants. 

Niemann-Pick disease Sphingomyeiinase Cer-i-P—choline Sphingomyelin Enlarged liver and spleen, mental retardation fatal in early life. 

All defects in urea synthesis result in ammonia intoxication. Intoxication is more severe when the metabolic block occurs at reactions 1 or 2 since some covalent linking of ammonia to carbon has already occurred if citrulline can be synthesized. Clinical symptoms common to all urea cycle disorders include vomiting, avoidance of high-protein foods, intermittent ataxia, irritability, lethargy, and mental retardation. The clinical features and treatment of all five disorders discussed below are similar. Significant improvement and minimization of brain damage accompany a low-protein diet ingested as frequent small meals to avoid sudden increases in blood ammonia levels. 

Homocarnosine (Figure 31-2), present in human brain at higher levels than carnosine, is synthesized in brain tissue by carnosine synthetase. Serum carnosinase does not hydrolyze homocarnosine. Homocarnosinosis, a rare genetic disorder, is associated with progressive spastic paraplegia and mental retardation. 

Figure 48-10. Simplified scheme of causation ofa mucopolysaccharidosis, such as Hurler syndrome (MIM 252800), in which the affected enzyme is a-L-iduroni-dase. Marked accumulation of the GAGs in the tissues mentioned in the figure could cause hepatomegaly, splenomegaly, disturbances of growth, coarse facies, and mental retardation, respectively.

Nineteen women underwent amniocentesis for the determination of fetal sex. Several different X-llnked abnormalities constituted the Indications for this procedure, and these Included hemophilia A, hemophilia B, Duchenne muscular dystrophy, optic albinism, X-llnked mental retardation, the Lesch-Nyhan syndrome (due to dlflclency of hypoxanthlne-guanlne phosphorlbosyltransferase, and Fabry s disease (due to deficiency of an a-galact-osldase). Fourteen of the fetuses were male. Including one which turned out to be a set of twins, and most of the male pregnancies were terminated. The sex determination being carried out for Fabry s disease Is of particular Interest, since In this case It was desired to find out whether the fetus was a female. 

Togaviruses Rubella Spherical particles 70 nm in diameter, a tightly adherent envelope surrounds an icosahedral capsid Causes German measles in children. An infection contracted in the early stages of pregnancy can induce severe multiple congenital abnormalities, e.g. deafness, blindness, heart disease and mental retardation... 

Lennox-Gostaut syndrome (LGS) Patients with this syndrome have cognitive dysfunction and mental retardation. Their seizures usually consist of a combination of tonic-clonic, absence, atonic, and myoclonic seizures. 

It is known that an association exists between maternal UTI during pregnancy and fetal death, mental retardation, and developmental delay.24 Because of this known association, and because up to 7% of pregnant women have an asymptomatic bacteriuria that may progress to pyelonephritis, screening is necessary. In patients with significant bacteriuria, whether symptomatic or asymptomatic, treatment is recommended to avoid the complications discussed above. In the majority... 

Otake M, Schull W. 1984. Mental retardation in children exposed in utero to the atomic bombs A reassessment. Technical Report RERF TR 1-83, Radiation Effects Research Foundation, Japan. 

GSH-S deficiency is a more frequent cause of GSH deficiency (HI7), and more than 20 families with this enzyme deficiency have been reported since the first report by Oort et al. (05). There are two distinct types of GSH-S deficiency with different clinical pictures. In the red blood cell type, the enzyme defect is limited to red blood cells and the only clinical presentation is mild hemolysis. In the generalized type, the deficiency is also found in tissues other than red blood cells, and the patients show not only chronic hemolytic anemia but also metabolic acidosis with marked 5-oxoprolinuria and neurologic manifestations including mental retardation. The precise mechanism of these two different phenotypes remains to be elucidated, because the existence of tissue-specific isozymes is not clear. Seven mutations at the GSH-S locus on six alleles—four missense mutations, two deletions, and one splice site mutation—have been identified (S14). 

Hereditary methemoglobinemia is classified into three types a red blood cell type (type I), a generalized type (type II), and a blood cell type (type HI). Enzyme deficiency of type I is limited to red blood cells, and these patients show only the diffuse, persistent, slate-gray cyanosis not associated with cardiac or pulmonary disease. In type II, the enzyme deficiency occurs in all cells, and patients of this type have a severe neurological disorder with mental retardation that predisposes them to early death. Patients with type III show symptoms similar to those of patients with type I. The precise nature of type III is not clear, but decreased enzyme activity is observed in all cells (M9). It is considered that uncomplicated hereditary methemoglobinemia without neurological involvement arises from a defect limited to the soluble cytochrome b5 reductase and that a combined deficiency of both the cytosolic and the microsomal cytochrome b5 reductase occurs in subjects with mental retardation. Up to now, three missense mutations in type I and three missense mutations, two nonsense mutations, two in-frame 3-bp deletions, and one splicing mutation in type n have been identified (M3, M8, M31). 

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