Browsing pathways

Ethylmalonic Encephalopathy(Epema Syndrome; EE) is a rare autosomal recessive disorder caused by a mutation in the ETHE1 gene which codes for protein ETHE1. A deficiency of this protein inhibits proper energy production in mitochondria and a deficiency in cytochrome c oxidase. This results in accumulation of 2-methylbutyrylglycine, N-butyrylglycine, isobutyrylglycine, isovalerylglycine, and methylsuccinic acid in urine. Concentrations of L-carnitine are reduced in plasma. Symptoms, which present at birth, include peripheral neuropathy, seizures, microcephaly, and hypotonia lead to premature death. Treatment includes riboflavin and L-carnitine.

Dimethylglycine Dehydrogenase Deficiency (DMGDH deficiency; Dimethylglycinuria) phenotype in the catabolism of choline, catalyzing the oxidative demethylation of dimethylglycine (DMG) to form sarcosine. A defect in DMGDH results in the accumulation of N,N-dimethylglycine and creatinine kinase in serum, and N,N-dimethylglycine in urine. Symptoms of this disease include an unusual odor and muscle weakness.

Dihydropyrimidine Dehydrogenase Deficiency (DHPD; Thymine-uraciluria) is a rare autosomal recessive disorder caused by a mutation in the DPYD gene which codes for dihydropyrimidine dehydrogenase. A deficiency in this enzyme results in accumulation of 5-hydroxymethyluracil, thymine, and uracil in urine. Symptoms include nystagmus, large liver, hypotonia, growth and mental retardation, and seizures.

Dihydropyrimidinase Deficiency(DHPA, Dihydropyrimidinuria Deficiency, DPH Deficiency) is an autosomal recessive disease caused by a mutation in the DPYS gene which codes for dihydropyrimidinase. A deficiency in this enzyme results in accumulation of dihydrothymine, dihydrouracil, thymine, and uracil in urine. Symptoms, which present at birth, include metabolic acidosis, difficulty feeding, and seizures.

Desmosterolosis is caused by a mutation in the DHCR24 gene, which codes for the enzyme 24-dehydrocholesterol reductase, which catalyzes the reduction of the delta-24 double bond of sterol intermediates. A defect in 24-dehydrocholesterol reductase causes accumulation of desmosterol in plasma. Symptoms include cleft palate, clubfoot, dysmorphism, mental and motor retardation, and speech development.

Cystathionine Beta-Synthase Deficiency(CBS Deficiency; Homocystinuria) is an autosomal recessive disease caused by a mutation in the CBS gene which codes for cystathionine beta-synthase. A deficiency in this enzyme results in accumulation of L-cystathionine, homocysteine, and L-homocystine in plasma and urine; and L-methionine and ornithine in plasma. Symptoms include osteoporosis, myopia, fatty-liver, mental retardation, and early death. Treatment includes folic acid, vitamin B6, vitamin B12, and a methionine-restricted diet.

Congenital lipoid adrenal hyperplasia (CLAH; Steroid 20-22 desmolase deficiency; lipoid CAH) is caused by a defect in the CYP11A1 gene which codes for mitochondrial cholesterol side-chain cleavage enzyme. Cholesterol side-chain cleavage enzyme convertes cholesterol to pregnenolone in adrenal cortisol synthesis of all steroid hormones. A defect in this enzyme results in in impaired synthesis of all three categories of adrenal steroids (cortisol, mineralocorticoids, sex steroids) and high levels of adrenocorticotropic hormone (ACTH). Symptoms include poor feeding, vomiting, dehydration, hypotension, hyponatremia, hyperkalemia, hypoglycemia, hyperpigmentation. Sex steroid deficiency can result in ambiguous genitalia. Patients need the mineral replacement and extra glucocorticoid. XX female patients can use estrogen replacement at or after puberty. For XY patients, the testes are uniformly nonfunctional and they are undescended, are removed when the diagnosis is made due to the risk of cancer development in these tissues.

Congenital Erythropoietic Porphyria (CEP) or Gunther Disease is a rare inborn error of porphyrin-heme synthesis inherited that is as an autosomal recessive trait. This disorder of bone marrow heme synthesis is caused by a defect in the UROS gene which codes for uroporphyrinogen-III synthase. This enzyme is involved in the fourth step of porphyrin metabolism, involved in the conversion of hydroxymethyl bilane into uroporphyrinogen III. Its defect results in accumulation of uroporphyrin III, coproporphyrin III and porphyrins; Uroporphyrin I in erythrocytes. Symptoms and signs include blistering and fragility of light-exposed skin, discolored urine, concomitant jaundice, reddish color teeth. The severe loss of bone with subsequent contractures and deformities occurs in most adults with erythropoietic porphyria.

Congenital Bile Acid Synthesis Defect Type III (CBASIII) is caused by a defect in 25-hydroxycholesterol 7-alpha-hydroxylase, which plays a role in synthesis of bile acids. The synthesis of primary bile acids from cholesterol occurs via two pathways: the classic neutral pathway involving cholesterol 7-alpha-hydroxylase (CYP7A1), and the acidic pathway involving a distinct microsomal oxysterol 7-alpha-hydroxylase (CYP7B1). CBASIII is characterized by accumulation of bile acids in the urine. Symptoms include severe cholestasis, cirrhosis, and liver failure.

Congenital Bile Acid Synthesis Defect Type II is a congenital defect in bile acid synthesis with delta(4)-3-oxosteroid 5-beta-reductase deficiency is caused by mutation in the AKR1D1 gene. 3-oxo-5-beta-steroid 4-dehydrogenase catalyzes the bile acid intermediates 7-alpha,12-alpha-dihydroxy-4-cholesten-3-one and 7-alpha-hydroxy-4-cholesten-3-one. Chenodeoxycholic acid and cholic acid are decreased in plasma and urine. Symptoms of this disease include cholestatic jaundice, atypical oxo and allo bile acids in urine and serum, liver failure, and steatosis.

Citrullinemia Type I, (Argininosuccinate Synthetase Deficiency, Citrullinuria, Citrullinemia, ASS) is an autosomal recessive urea cycle disorder that causes ammonia and other toxic substances to accumulate in the blood. Two forms of citrullinemia have been described, both having different signs and symptoms, and are caused by mutations in different genes. Citrullinemia belongs to a class of genetic diseases called urea cycle disorders. The urea cycle is a sequence of chemical reactions that takes place in the liver. These reactions process excess nitrogen, generated when protein is used by the body, to make a compound called urea that is excreted by the kidneys. Citrullinemia Type I is an autosomal recessive disease caused by mutation in the ASS gene which codes for argininosuccinate synthetase. A deficiency in this enzyme results in accumulation of citruilline as well as glycine and orotic acid in urine. Infants appear normal at birth, but within the first week of life symptoms such as feeding difficulties, irritability, hypotonia, seizures, and vomiting present and eventually lead to premature death.

Chondrodysplasia Punctata 2, X Linked Dominant (CDPX2; CPDXD; CPXD; Conradi-Hunermann Syndrome; Happle Syndrome; Conradi-Hunermann-Happle Syndrome is caused by a mutation in the gene encoding delta(8)-delta(7) sterol isomerase emopamil-binding protein (EBP). EBP contains the code for the enzyme 3-beta-hydroxysteroid-Delta(8),Delta(7)-isomerase, which normally catalyzes the conversion of Delta(8)-sterols to their corresponding Delta(7)-isomers. A defect in this enzyme causes accumulation of 8-dehydrocholesterol and 8(9)cholestenol in the plasma. Symptoms include alopecia, dysmorphism, hyperkeratosis, ichthyosis, kyphoscoliosis, limb abnormalities and deformities, and mental retardation.

CHILD Syndrome, (Congenital Hemidysplasia with Icthyosiform Erythroderma and Limb Defects; Ichthyosiform Eruthroderma, Unilateral, with Epsilateral Malformations, Especially Absence Deformity of Limbs) is caused by a mutation in the gene encoding NAD(P)H steroid dehydrogenase-like protein (NSDHL). A defect in sterol-4 alpha-carboxylate 3-dehydrogenase, which normally catalyzes the reaction 3-beta-hydroxy-4-beta-methyl-5-alpha-cholest-7-ene-4-alpha-carboxylate + NAD(P)+ = 4-alpha-methyl-5-alpha-cholest-7-en-3-one + CO2 + NAD(P)H, causes accumulation of 8(9)cholestenol and 8-dehydrocholesterol in plasma. Symptoms of CHILD syndrome include hearing defects, hemidysplasia, unilateral hypomelia, ichthyosiform nevi, limb abnormalities, lung hypoplasia, and punctate calcifications.

Cerebrotendinous Xanthomatosis is caused by mutation in the CYP27A1 gene, which encodes sterol 27-hydroxylase. This enzyme catalyzes the first step in the oxidation of the side chain of sterol intermediates; the 27-hydroxylation of 5-beta-cholestane-3-alpha,7-alpha,12-alpha-triol. Cerebrotendinous Xanthomatosis is a rare, inherited lipid-storage disease with large deposits of cholesterol and cholestanol are found in virtually every tissue, particularly the Achilles tendons, brain, and lungs. Symptoms include progressive neurologic dysfunction (cerebellar ataxia beginning after puberty, systemic spinal cord involvement and a pseudobulbar phase leading to death), premature atherosclerosis, and cataracts.

Carbamoyl phosphate synthetase (CPS) deficiency(Carbamoyl phosphate synthetase I deficiency) is a urea cycle defect that results from a deficiency in an enzyme that mediates the normal path for incorporation of ammonia. Carbamoyl phosphate is derived from catabolism of amino acids into a 1-carbon compound, in which the carbon atom is derived from bicarbonate. The process is exclusively mitochondrial and requires the expenditure of two ATP molecules. Two hepatocellular enzymes exist: CPS I and CPS II. CPS I is exclusively intramitochondrial, and its deficiency is responsible for the disease. CPS I is the most plentiful single protein in hepatic mitochondria, accounting for about 20% of the matrix protein. CPS II is exclusively cytosolic and is an important enzyme in de novo synthesis of pyrimidine nucleotides. The regulation of CPS I activity depends on the levels of N -acetylglutamate. In patients with homozygous CPS I deficiency, the ability to fix waste nitrogen is completely absent, resulting in increasing levels of free ammonia with the attendant effects on the CNS. A recent molecular and functional examination of the mutational effects showed that, although some mutations affect both substrate affinity and efficiency of the reaction, others affect one more than the other. Some mutations are associated with enhanced RNA instability, which leads to diminished protein synthesis. The hepatic urea cycle is the major route for waste nitrogen disposal. Waste nitrogen is chiefly generated from protein and amino acid metabolism. Low-level synthesis of certain cycle intermediates in extrahepatic tissues also makes a small contribution to waste nitrogen disposal. A portion of the cycle is mitochondrial in nature; mitochondrial dysfunction may impair urea production and may result in hyperammonemia. Overall, activity of the cycle is regulated by the rate of synthesis of N -acetylglutamate, the enzyme activator of CPS I, which initiates incorporation of ammonia into the cycle.

Canavan Disease (Canavan-Van Bogaert-Bertrand Disease; Aminoacylase 2 Deficiency; Spongy Degeneration of the Central Nervous System; Aspartoacylase Deficiency; ASP Deficiency; ACY2 Deficiency; ASPA) is a rare autosomal recessive disease caused by a defect in the ASPA gene which codes for aspartoacylase. A deficiency in this enzyme results in accumulation of N-Acetyl-L-aspartic acid in plasma, spinal fluid, and urine. Symptoms, which present at birth, include myclonus, irritability, hypotonia, motor retardation, and poor head control. The neurological complications are due to demyelination of neurons and leukodystrophy. Premature death often results, though lithim citrate can be used as a treatment.

Biotinidase deficiency (Multiple carboxylase deficiency) is an autosomal recessive disease caused by a mutation in the BTD gene which does for biotinidase. A deficiency in this enzyme results in accumulation of ammonia and ketone bodies in blood; 3-hydroxyisovaleric acid in plasma, spinal fluid, and urine; hydroxypropionic acid, 2-hydroxybutyric acid, 3-Hydroxybutyric acid, and citric acid in spinal fluid; and 3-methylcrotonylglycine, hydroxypropionic acid, and L and D-lactic acid in urine. Symptoms, which can present from birth into adulthood include hypotonia, ketosis, hyperammonemia, motor retardation, coma, and seborrhoic skin rush. Treatment includes biotin.

Beta-Ketothiolase Deficiency (2-Methyl-3-Hydroxybutyric Acidemia; Mitochondrial Acetoacetyl-CoA Thiolase Deficiency; MAT Deficiency; T2 Deficiency; 3-KTD Deficiency; 3-Ketothiolase Deficiency) is an autosomal recessive disease caused by a mutation in the HADHB gene which codes for beta-ketathiolase. A deficiency in this enzyme results in accumulation of ammonia and ketone bodies in blood; and 2-methyl-3-hydroxybutyric acid, 2-methylacetoacetic acid, 3-hydroxybutyric acid, tiglylglycine, and ketone bodies in urine. Symptoms include ketosis, seizures, organic acids in urine, and hyperammonemia. Treatment includes a low protein diet and L-carnitine.h3. h2.

Beta-ureidopropionase deficiency (Beta Alanine-Synthase Deficiency, UPB1, BUP1) is an autosomal recessive disease caused by mutations in the UPB1 gene which codes for beta-ureidopropionase. A deficiency in this enzyme results in accumulation of N-carbamyl-beta-amino acids. Symptoms include hypotonia, dystonic movements, scoliosis, microcephaly, and severe developmental delay.

Aspartylglucosaminuria is an autosomal recessive disorder of lysosomal storage caused by a mutation in the AGA gene which codes for N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase. A deficiency in this enzyme results in accumulation of aspartylglycosamine and oligosaccharides in urine. Symptoms, which present in childhood, include skeletal changes, speech abnormalities, macroglossia, and mental retardation. Treatment includes bone marrow transplants.

Aromatic L-Aminoacid Decarboxylase Deficiency(Dopa decarboxylase; DDC) is an autosomal recessive disease caused by a mutation in the DDC gene which codes for aromatic-L-aminoacid decarboxylase. A deficiency in this enzyme results in accumulation of 3-methoxytyrosine, 5-hydroxy-L-tryptophan, and L-Dopa in plasma, spinal fluid, and urine; 3-methoxytyramine and dopamine in urine. It also results in decreased concentrations of homovanillic acid, S-adenosylmethionine, and 5-hydroxytryptophol in spinal fluid; and epinephrine, norepinephrine in plasma. Symptoms include temperature instability, hypotonia, mental and motor retardation, and cerebral atrophy.

Argininosuccinic Aciduria, (Argininosuccinase Deficiency, Argininosuccinate Lyase Deficiency, ASL Deficiency) is an autosomal recessive disorder caused by a mutation in the ASL gene which codes for argininosuccinate lyase. It results in accumulation of citrulline, arginosuccinic acid, L-arginine, and L-glutamic acid in plasma as well as ammonia in blood. Infants are lethargic and unwilling to eat. They may develop seizures, coma, and failure to thrive as toxic ammonia accumulates.

Argininemia is caused by a mutation in the gene ARG, encoding liver arginase, which hydrolyses arginine to urea and ornithine in the last step of the urea cycle. A defect in liver arginase causes accumulation of ammonia in blood; arginine, creatine, guanidinoacetate, and homoarginine in plasma; urea nitrogen in serum; arginine and homoarginine in spinal fluid; and arginiosuccinate orotic acid, and uracil in urine. Symptoms include ataxia, cerebral atrophy, chorea, jaundice, and seizures.

Arginine: Glycine Amidinotransferase Deficiency(AGAT Deficiency, Creatine Deficiency Syndrome, Creatine Deficiency due to AGAT Deficiency, GATM Deficiency) is caused by mutation in the GATM gene, which codes for L-arginine:glycine amidinotransferase, which catalyzes the reaction between L-arginine and glycine, transferring an amidino group from L-arginine to glycine, producing L-ornithine and guanidinoacetate, a precursor of creatine. A defect in this enzyme causes a decrease in concentration of creatine and guanidinoacetate in plasma and urine. Symptoms include mental and motor retardation, seizures, and delayed or abnormal speech development.

Alkaptonuria (Homogentisic acid oxidase deficiency) is an autosomal recessive disease caused by a mutation in the HGD gene which codes for homogentisate 1,2-dioxygenase. A mutation in this enzyme results in accumulation of homogentisic acid in urine. Symptoms, which present in adulthood, include arthritis, black or brown urine, and urolithiasis. Treatment includes a low-protein diet with vitamin C.