Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tyrosinemia type III (OMIM 276710) is an autosomal recessive disorder caused by the deficiency of 4-hydroxyphenylpyruvate dioxygenase (HPD), the second enzyme in the tyrosine catabolic pathway. The enzyme deficiency results in an accumulation and increased excretion of tyrosine and phenolic metabolites. Only a few cases with the disorder have been described, and the clinical spectrum of the disorder is unknown. Reported patients have presented with mental retardation or neurological symptoms or have been picked up by neonatal screening. We have identified four presumed pathogenic mutations (two missense and two nonsense mutations) in the HPD gene in three unrelated families encompassing four homozygous individuals and one compound heterozygous individual with tyrosinemia type III. Furthermore, a number of polymorphic mutations have been identified in the HPD gene. No correlation of the severity of the mutation and enzyme deficiency and mental function has been found; neither do the recorded tyrosine levels correlate with the clinical phenotype.
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PMID:Mutations in the 4-hydroxyphenylpyruvate dioxygenase gene (HPD) in patients with tyrosinemia type III. 1094 15

Tyrosinemia type III (OMIM 276710) is an autosomal recessive disorder caused by the deficiency of 4-hydroxyphenylpyruvate dioxygenase (4-HPD). Few cases have been described with mental retardation or neurological symptoms. Recently it has been demonstrated that 4-HPD participates to nitric oxide (NO) intracellular sequestration in Pseudomonas aeruginosa. 4-HPD is an ubiquitous enzyme with a prominent expression in neutrophils and neurons. In the nervous system NO has been perceived to be a potential neuromodulator although prolonged excessive generation is detrimental. We analyzed NO release by neutrophils of a patient with tyrosinemia type III in order to evaluate a possible influence of 4-HPD deficiency on this process. Our patient, previously described, is a 30-year-old women with persistent tyrosinemia (450-680 micromol/l) and deficient activity of 4-HPD. At 17 months of age she experienced an acute ataxia and drowsiness lasting for 10 days, but further clinical course showed persistent tyrosinemia with normal growth and psychomotor development. Neutrophils isolated from our patient exhibited a NO release greatly higher in respect to the controls (mean+/-SEM 23.2+/-1.8 micromol/10(6) cells vs 3.5+/-0.5 micromol/10(6) cells). Clinical findings of tyrosinemia type III include neurological symptoms and mental retardation but no consistent phenotype has emerged. Therefore the pathogenesis of neurological involvement is yet not well understood. Our results suggest that an excessive neutrophils of NO release could reflect the lack of scavenging action of 4-HPD. Considering the prominent expression of this enzyme in neurons, we hypothesize that excessive NO release could participate in neuronal damage explaining the neurological involvement described in patients with tyrosinemia type III.
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PMID:Increased nitric oxide release by neutrophils of a patient with tyrosinemia type III. 1865 47

Tyrosinemia type III is an autosomal recessive disorder caused by the deficiency of 4- hydroxyphenylpyruvate dioxygenase (4-HPPD). It is characterized by elevated levels of blood tyrosine and massive excretion of its derivatives into the urine. Clinical findings of tyrosinemia type III include neurological symptoms and mental retardation. Only a few patients presenting with this disease have been described, and the clinical phenotype remains variable and unclear. We present a case, who was admitted to the hospital at the age of 4 months for recurrent seizures. Two months later, she was admitted again with status epilepticus. Laboratory data showed increased level of tyrosine in the blood. She was treated with a diet low in tyrosine and phenylalanine and anamix formula that leading to catch-up growth and improvement of her symptoms. Plasma tyrosine level dropped to normal values. In any child who presents with the neurologic symptom, some rare diagnosis like tyrosinemia type III should be considered.
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PMID:A Case of Tyrosinemia Type III with Status Epilepticus and Mental Retardation. 2945 78