tyrosinemia(redirected from Hereditary Tyrosinemias)
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an aminoacidopathy consisting of defective metabolism of tyrosine and its buildup in the body, as well as urinary excretion of related metabolites. Several forms exist: Type I is an autosomal recessive trait with an acute form that is usually fatal in infancy and a chronic form characterized by chronic liver and kidney disease, rickets, and death in childhood. Type II is an oculocutaneous syndrome with crystallization of accumulated tyrosine in the epidermis as palmoplantar hyperkeratoses and in the corneas as herpetiform ulcers, often accompanied by mental retardation.
ty·ro·si·ne·mi·a(tī'rō-si-nē'mē-ă), [MIM*276600, *276700, and *276710]
A group of autosomal recessively inherited disorders of tyrosine metabolism associated with elevated blood concentration of tyrosine, and enhanced urinary excretion of tyrosine and tyrosyl compounds. Type I tyrosinemia, due to deficiency of fumarylacetoacetase (FAH), is characterized by hepatosplenomegaly, nodular liver cirrhosis, multiple renal tubular reabsorptive defects, and vitamin D-resistant rickets; caused by mutation in the FAH gene on chromosome 15q. Type II tyrosinemia, due to deficiency of tyrosine aminotransferase (TAT), is characterized by corneal ulcers and keratosis of digits, palms, and soles; caused by mutation in the TAT gene on 16q. Type III tyrosinemia is associated with intermittent ataxia and drowsiness without liver dysfunction and is due to 4-hydroxy-phenylpyruvate dioxygenase (4HPPD) deficiency.
[tyrosine + G. haima, blood]
tyrosinemia/ty·ro·sin·e·mia/ (ti″ro-sĭ-ne´me-ah) an aminoacidopathy of tyrosine metabolism with elevated blood levels of tyrosine and urinary excretion of tyrosine and related metabolites. Type I shows inhibition of some liver enzymes and renal tubular function. Type II is marked by crystallization of the accumulated tyrosine in the epidermis and cornea and is frequently accompanied by mental retardation. Neonatal t. is asymptomatic, transitory, and may result in mild mental retardation. The fourth type is hawkinsinuria .
Etymology: Gk, tyros + haima, blood
1 a benign, transient condition of the newborn, especially premature infants, in which an excessive amount of the amino acid tyrosine is found in the blood and urine. The disorder is caused by an anomaly in amino acid metabolism, usually delayed development of the enzymes necessary to metabolize tyrosine, and is controlled by dietary measures and vitamin C therapy. The metabolic defect disappears with treatment, or it may disappear spontaneously. Also called neonatal tyrosinemia.
2 a hereditary disorder involving an inborn error of metabolism of the amino acid tyrosine. The condition, which is transmitted as an autosomal-recessive trait, is caused by an enzyme deficiency and results in liver failure or hepatic cirrhosis, renal tubular defects that can lead to renal rickets and renal glycosuria, generalized aminoaciduria, and mental retardation. Treatment consists of a diet low in tyrosine and phenylalanine and high in vitamin C. In severe cases prognosis is extremely poor, and a liver transplantation may be the only lifesaving measure. Also called hereditary tyrosinemia.
ty·ro·si·ne·mi·a(tī'rō-si-nē'mē-ă) [MIM*276600, *276700, and *276710]
Inherited disorders of tyrosine metabolism associated with elevated blood concentration of tyrosine and enhanced urinary excretion of tyrosine and tyrosyl compounds.
[tyrosine + G. haima, blood]
an excess of tyrosine in the blood. Several different types with varying clinical features occur in humans. A syndrome of dermatitis and keratoconjunctivitis resembling tyrosinemia type II of humans (Richner-Hanhart syndrome) occurs in rats fed a diet high in tyrosine, in mink as an inherited disorder (called also pseudodistemper) and it has been reported in a dog.