Browsing Pathways

Carnosinemia, also known as carnosinemia, is a rare inborn error of metabolism (IEM) and recessive autosomal disorder caused by a defective CNDP1 gene which encodes for carnosinase. Carnosinase is a dipeptidase enzyme that catalyzes the breakdown of Carnosine into alanine and histidine. This disorder is characterized by secretion of large amounts of carnosine and anserine in the urine but low levels of methylhistidine. Patients also have unusually high concentrations of homocarnosine in the cerebrospinal fluid. Other symptoms include progressive neurologic disorders characterized by severe mental defect and myoclonic seizures. There is no known cure for Carnosinemia therefore treatment involves management of symptoms. There have been about 30 cases of Carnosinemia reported worldwide.

A transient defect in tyrosine metabolism is a common aminoacidopathy in the premature and full-term human infant. This disorder, termed neonatal tyrosinemia, was first described by Levine and Gordon in 1939. In the intervening years other workers have studied this disorder, and have noted the concurrence of tyrosinemia and tyrosyluria. In a current survey of 15,000 infants, 6 mild tyrosinemia occurred during the first week of life in 10% of full-term infants, and severe tyrosinemia occurred in approximately 30% of premature infants. The enzymatic basis of neonatal tyrosinemia is complex and involves the susceptibility of p-hydroxyphenylpyruvic acid oxidase to inhibition in the presence of its substrate, p-hydroxyphenylpyruvic acid and derivatives. The inhibition is reversible by removal of excess substrate and by reducing agents such as ascorbic acid, 2, 6-dichiorophenolindophenol, and a number of hydroquinone and phenylenediamine compounds.

Galactokinase deficiency also called Galactosemia type II, is a rare inborn error of metabolism (IEM) and an autosomal recessive disorder of galactokinase caused by a mutation in the GALK1 gene on chromosome 17q24. Galactokinase uses 1 ATP to catalyse the phosphorylation of α-D-galactose to galactose 1-phosphate and catalyses β-D-galactose to glucose 1-phosphate. Symptoms include cataract formation in children who are exposed to lactose in their diets. Cataract formation is the result of osmotic phenomena caused by the accumulation of galactitol in the lens. Treatment includes immediately removing lactose from patient’s diet, however symptoms such as delayed speech, cognitive learning and motor skills can still be present.

Galactosemia III also called GALE deficiency or UDP-Galactose-4-Epimerase deficiency, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder caused by either a homozygous or compound heterozygous mutation in the UDP-galactose-4-epimerase (GALE) gene. GALE catalyses the reversible conversion of UDP-galactose to UDP-glucose in galactose metabolism. Symptoms are similar to classic galactosemia, including jaundice, vomiting, hypotonia, failure to thrive, hepatomegaly, moderate generalized amino aciduria and marked galactosuria. Treatment usually includes galactose restricted diets instead of galactose free diets in the management of this disorder because unlike patients with galactokinase deficiency and classic galactosemia, patients with galactose epimerase deficiency cannot utilize the endogenous pathway for synthesis of UDP-galactose. This makes patients dependent on exogenous galactose.

Tyrosine Hydroxylase (TH) Deficiency is a rare inborn error of metabolism (IEM) and autosomal recessive disorder of catecholamines pathways. The disorder is caused by defects in the Tyrosine hydroxylase (TH) gene which encodes for the enzyme tyrosine hydroxylase. This enzyme is part of the production of catecholamines such as dopamine, norepinephrine and epinephrine are all essential for normal nervous system function. Dopamine transmits signals to help the brain control physical movement and emotional behavior. Norepinephrine and epinephrine are involved in the autonomic nervous system. Mutations in the TH gene result in reduced activity of the tyrosine hydroxylase enzyme. As a result, the body produces less dopamine, norepinephrine and epinephrine. Symptoms of the disorder include abnormal movements, autonomic dysfunction, and other neurological problems. Treatments can include the administration of levodopa; however patient responses can vary greatly. The frequency of Tyrosine Hydroxylase Deficiency is unknown.

Dopamine beta-hydroxylase deficiency (or norepinephrine deficiency) is caused by mutation in the gene encoding dopamine beta-hydroxylase. Clinical features include orthostatic hypotension, ptosis, nasal stuffiness, and a neonatal history of delayed eye opening. Noradrenaline and adrenaline are generally not detectable in plasma, urine, and cerebrospinal fluid, but dopamine is increased 7- to 12-fold in plasma, 4-fold in urine, and 20-fold in CSF. Treatment with dihydroxyphenylserine has been shown to reduce symptoms and signs of postural hypotension and increase plasma levels of noradrenaline.

Metcaptolactate-cysteine disulfiduria (MCDU) is an autosomal disorder that leads to the loss of function of the enzyme mercaptopyruvate sulfurtransferase. The condition is characterized by the urinary excretion of large amounts of a sulfur-containing amino acid, which is beta-mercaptolactate-cysteine disulfide. Patients exhibit a low IQ, grand mal seizures, flattened nasal bridge, and an excessively arched palate.

5-Oxoprolinase deficiency, also called OPLAHD, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder of glutathione metabolism caused by a defective 5-oxoprolinase. 5-Oxoprolinase catalyzes the conversion of 5-oxoproline into glutamate which is an important neurotransmitter. This disorder is characterized by a large accumulation of 5-oxoproline in the urine. Symptoms of the disorder include enterocolitis, mental retardation, kidney stone formation, and hypoglycemia. 5-Oxoprolinase deficiency has been reported in approximately 8 people.

Gamma-glutamyltranspeptidase deficiency, characterized by glutathionemia and glutathionuria, is an autosomal recessive disorder of glutathione metabolism caused by a defective gamma-glutamyl transpeptidase (GGT). GGT transfers glutamyl moieties to acceptor molecules such as amino acids and peptides. This disorder is characterized by a large accumulation of glutathione in the urine. Symptoms of the disorder include easy bruising, asthma, and mild mental retardation.

Malonyl CoA decarboxylase deficiency, also claled MCD deficiency, is a rare inborn error of fatty acid metabolism and autosomal-recessive metabolic disorder, which is caused by a defective mitochondrial malonyl CoA decarboxylase due to reduced activity. Mitochondrial malonyl CoA decarboxylase catalyzes the conversion of intramitochondrial malonyl CoA to acetyl CoA, which is a key product that involve in many biochemical reactions. This disorder is characterized by a large accumulation of methylmalonic acid in the mitochondrial. Symptoms of the disorder include hypotonia (i.e. weak muscle tone), hypoglycemia (i.e. low blood sugar), diarrhea, seizures and vomiting. The Malonyl CoA decarboxylase deficiency is an extremely rare genetic disease happened in early childhood, which only less than 30 cases have been reported. There is currently no cure for Malonyl CoA decarboxylase deficiency, treatment involves managing the disorder's symptoms.