Inborn errors

Deficiency or Toxicity in Humans. Molybdenum deficiency in humans results in deranged metaboHsm of sulfur and purines and symptoms of mental disturbances (130). Toxic levels produce elevated uric acid in blood, gout, anemia, and growth depression. Faulty utiH2ation results in sulfite oxidase deficiency, a lethal inborn error. 

Clinical stresses which interfere with vitamin metabohsm, can result in calcium deficiency leading to osteomalacia and osteoporosis (secondary vitamin D deficiency). These stresses include intestinal malabsorption (lack of bile salts) stomach bypass surgery obstmctive jaundice alcoholism Hver or kidney failure decreasing hydroxylation of vitamin to active forms inborn error of metabohsm and use of anticonverdiants that may lead to increased requirement. 

Erythrocyte Entrapment of Enzymes. Erythrocytes have been used as carriers for therapeutic enzymes in the treatment of inborn errors (249). Exogenous enzymes encapsulated in erythrocytes may be useful both for dehvery of a given enzyme to the site of its intended function and for the degradation of pathologically elevated, diffusible substances in the plasma. In the use of this approach, it is important to determine that the enzyme is completely internalized without adsorption to the erythrocyte membrane. Since exposed protein on the erythrocyte surface may ehcit an immune response following repeated sensitization with enzyme loaded erythrocytes, an immunologic assessment of each potential system in animal models is required prior to human trials (250). 

Epilepsy may be defined as a permanent, recurrent seizure disorder. Examples of the known causes of epilepsy include brain injury at birth, head injuries, and inborn errors of metabolism, hi some patients, the cause of epilepsy is never determined. 

Garrod AE Inborn errors of metabolism. (Croonian Lectures.) Lancet 1908 2 1,73, 142,214. 

Van den Berghe G Inborn errors of fructose metabolism. Annu Rev Nutr 1994 l4 4l. 

Hepatic urea synthesis takes place in part in the mitochondrial matrix and in part in the cytosol. Inborn errors of metabolism are associated with each reaction of the urea cycle. 

As is true of most inborn errors, the signs and symptoms of porphyria result from either a deficiency of metabohc products beyond the enzymatic block or from an accumulation of metabolites behind the block. 

Understanding of the degradative pathways for GAGs, as in the case of glycoproteins (Chapter 47) and glycosphingohpids (Chapter 24), has been gready aided by elucidation of the specific enzyme deficiencies that occur in certain inborn errors of metabolism. When GAGs are involved, these inborn errors are called mucopolysaccharidoses (Table 48—7). 

Inborn errors of fatty acid oxidation Carnitine entry into cells and mitochondria Certain enzymes of fatty acid oxidation... 

Phenylketoniuia (PKU) is an inborn error of metabolism by which the body is unable to convert siuplus pherylalanine (PA) to tyrosine for use in the biosynthesis of, for... 

Other diseases Autoimmune diseases Amyloidosis Aplastic anemia Paroxysmal nocturnal hemoglobinuria Fanconi s anemia Thalassemia major Sickle cell anemia Severe combined immunodeficiency Inborn errors of metabolism... 

Sepsis syndrome Anorexia nervosa Complications during pregnancy Geriatric patients with multiple chronic disease Organ transplantation Inborn errors of metabolism Cystic fibrosis Extreme prematurity... 

Lead has been shown to decrease circulating levels of the active form of vitamin D (1,25-dihydroxy-vitamin D) in children. The conversion of vitamin D to this active hormonal form takes place via hydroxylation to 25-hydroxyvitamin D in the liver, followed by 1-hydroxylation in the mitochondria of the renal tubule by a complex cytochrome P-450 (heme-containing) system (Mahaffey et al. 1982 Rosen and Chesney 1983). Comparisons of the serum 1,25-dihydroxyvitamin D levels in children with blood lead levels of 33 g/dL with those in children with severe renal insufficiency (Rosen et al. 1980) and in children with an inborn error of vitamin D metabolism in which the 1-hydroxylase system or component... 

Nyhan, W. L. The recognition of Lesch-Nyhan syndrome as an inborn error of purine metabolism. /. Inherit. Metab. Dis. 20 171-178,1997. 

Brusilow, S., Tinker, J. and Batshaw, M. L. Amino acid acylation A mechanism of nitrogen excretion in inborn errors of urea synthesis. Science 207 659,1980. 

MATSUMOTO, I., KAHURA, T., A new chemical diagnostic method for inborn errors of metabolism by mass spectrometry - rapid, practical, and simultaneous urinary metabolites analaysis, Mass Spec. Reviews, 1996,15,43-57. 

RASHED, M.S., BUCKNALL, M.P., LITTLE, D., AWAD, A., JACOB, M., ALAMOUDI, M., ALWATTAR, M., OZAND, P.T., Screening blood spots for inborn errors of metabolism by electrospray tandem mass spectrometry with a microplate batch process and a computer algorithm for automated flagging of abnormal profiles, Clin. Chem., 1997,43,1129-1141. 

The Editors have striven, as in previous years, to include in the present volume reviews on greatly diversified subjects, all of timely importance. The article on mellituria in Volume 4 has been supplemented by a survey of galactosemia, and we expect to follow in future volumes with reviews of other inborn errors of metabolism or, in modern parlance, of molecular diseases. Likewise, the article on peptiduria supplements that on aminoaciduria in Volume 2 and that on microbiological assay of vitamins extends previous summaries on the nucleogenic vitamins. The haptoglobins lie on the borderline of hematology. 

The One Gene One Enzyme Principle Garrod (G3, G4) suggested, over 50 years ago, that an inborn error of metabolism was caused by the inherited absence of an enzyme. This... 

G3. Garrod, A. E., The Croonian lectures on inborn errors of metabolism. II. Alkaptonuria. Lancet ii, 73-79 (1908). 

Isselbacher, K. J., cited by Kalckar, H. M., and Maxwell, G. S., Biosynthesis and metabolic function of uridine diphosphoglucose in mammalian organisms and its relevance to certain inborn errors. Physiol. Revs. 38, 88 (1958). 

The direct oxidative pathway involves 2 dehydrogenase systems that are of clinical interest because of the inborn errors, lacks and deficiencies of the enzymes involved. This hereditary trait, often race linked, leads to metabolic disorders accompanied by innocuous as well as by dangerous and severe symptoms. 

Pentosuria was classified as an inborn error of metabolism in 1908 by Garrod (Gl). The harmless metabolic condition has been described almost exclusively in individuals of Jewish origin. 

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