Metabolic Errors Word Scramble
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Question | Answer |
Three functions of metabolism | Obtaining energy from food, breakdown and detoxification of waste products, synthesis and breakdown of complex molecules |
Pathogenesis | intoxications, acute or progressive, accumulation of toxic compounds, problems of energy metabolism |
Pathogenesis | symptoms from deficiency in energy production or utilization, problems of complex molecules |
Pathogenesis | disturbed synthesis or catabolism, symptoms are permanent and progressive |
Inheritance | autosomal recessive |
Exceptions in inheritance x-linked recessive | ornithine transcarbamylase (OTC), Hunter syndrome |
Clinical presentation patterns | uncommon to note defects at birth, symptom free period, early and late signs |
Early signs | energy deficits, toxic products, obtundation, vomiting, seizures, brain damage |
Late signs | Accumulated material, cell damage, seizures, brain damage |
Typical signs and symptoms | very nonspecific, depends on genetic defect and environment |
late adult onset signs are | variable |
New born Screening Intoxications | Amino acid disorders (some), Organic acidurias, Some urea cycle defects |
Newborn screening energy metabolism defects | fatty acid oxidation defects |
NOT identified on Newborn Screening | Complex molecule defects, Glycogen metabolism defects, Congenital lactic acidosis, Mitochondrial defects |
Amino acid and organic acid metabolism disorders | Group of inherited disorders involved in the catabolism of selected amino acids and other compounds. Individually rare. Varied presentations |
Clinical features of amino acid and organic acid metabolism disorders | Acute presentation, neurological signs, Insidious onset, missing milestones- PKU, chronic skin problems, abnormality of routine labs |
Acute presentation | MSUD (maple syrup urine disease), Either in neonatal period or later in life, May be recurrent problem |
Clinical features of amino acid and organic acid metabolism disorders Neurological signs | Seizures, Mental retardation, Ataxia, Abnormal tone |
Clinical features of amino acid and organic acid metabolism disorders Abnormality of routine labs | Anion gap metabolic acidosis, Hypoglycemia, Hyperammonemia |
Amino acid and organic acid metabolism disorders Diagnosis | Screening for specific organic acids detected by chromatography or mass spectrometry, Abnormal amino acid levels in the blood and/or urine, Enzyme (or other biochemical) testing based on screening test results |
Amino acid and organic acid metabolism disorders Treatments | vary Low protein diet, Special formula without offending amino acids, Vitamins or cofactors |
Amino acid and organic acid metabolism disorders Phenylketonuria (PKU) | Prototype for screening and management, Phenylalanine (Phe) is an essential amino acid, most common disorder of amino acid metabolism, caused by deficiency of hepatic phenylalanine hydroxylase, which converts phenylalanine to tyrosine |
other disorders with elevated plasma phenylalanine | hyperphenylalaninemia and disorders of pteridine biosynthesis resulting in deficient cofactor levels |
PKU Clinical features | if untreated, mental retardation, seizures, autism, microcephaly, decreased skin pigmentation, musty odor |
PKU Laboratory findings/diagnosis | high serum phenylalanine > 20 mg/dl (normal <2 mg/dl), low serum tyrosine, Classic PKU has normal pteridine cofactor. |
PKU Newborn screening | Blood spots on filter paper. Tandem mass spectrometry to quantitate amount of Phe present |
PKU Treatment | low phenylalanine diet for life; if started early in infancy, can prevent significant mental retardation |
PKU Inheritance | autosomal recessive, chromosome 12q |
Maternal PKU | teratogenic effects on fetus from elevated maternal, phenylalanine (microcephaly 73%; congenital heart disease 12-15%; low birth weight 40-50%; mental retardation 70-90%) |
Carbohydrate disorders Galactosemia Etiology | caused by deficiency of galactose-1-phosphate uridyltransferase (GALT), which in turn causes an increase in galactose and galactose-1-phosphate. Less common forms of galactosemia caused by galactokinase and epimerase deficiencies |
Galactosemia Incidence | 1/30,000 - 1/100,000 |
Galactosemia Clinical features | vomiting and diarrhea in 1st weeks of life, liver disease with jaundice can progress to failure, cataracts, sepsis E.coli |
Galactosemia Diagnosis | newborn screening- direct enzyme assay of RBCs, florumetic determination of enzyme amount |
Galactosemia Treatment | galactose/lactose-free diet (soy formula) |
Urea cycle disorders | Six enzyme deficiencies |
Urea cycle disorders | N-acetyl-glutamate synthetase deficiency (NAGS) |
Urea cycle disorders | Carbamoylphosphate synthetase deficiency (CPS), |
Urea cycle disorders | Ornithine transcarbamylase deficiency (OTC), |
Urea cycle disorders | Argininosuccinic synthase deficiency (Citrullinemia) |
Urea cycle disorders | Argininosuccinic lyase deficiency (ASA) |
Urea cycle disorders | Arginase deficiency (Argininemia) |
Urea cycle disorders Symptoms | caused by deficiency of enzymes in the urea cycle, which metabolizes waste nitrogen (ammonia) formed from protein turnover or ingestion. High ammonia results in toxicity to the CNS. |
urea cycle disorders Diagnosis | hyperammonemia, increased glutamine and elevated or decreased citrulline and arginine on serum amino acids, with some abnormalities on urine organic acids. |
urea cycle Clinical features | lethargy, poor feeding, vomiting, coma and death |
urea cycle disorders Ornithine transcarbamylase (OTC) deficiency | 2nd enzyme in the urea cycle; catalyzes carbamyl phosphate + ornithine to form citrulline OTC inheritance |
OTC Untreated | coma and cerebral edema and death, Outcome depends on how long patient with elevated ammonia. |
OTC Treatment | low protein diet, medications for alternative pathways for nitrogen removal; arginine or citrulline |
• Fatty acid oxidation | primary source of energy for skeletal and cardiac muscle during fasting. Provides ketone bodies rather than glucose. |
• Oxidation in the mitochondria mediated by | acyl-CoA dehydrogenases in progressive shortening of the fatty acid chain |
• Fatty acid oxidation disorders Clinical features | hypoglycemia with fasting or increased metabolic demands; cardiomyopathy may occur; may present as sudden death |
• Fatty acid oxidation disorders Diagnosis | urine organic acids, plasma acylcarnitine profile- some detected on NBS with tandem mass spectrometry |
• Fatty acid oxidation disorders Inheritance | autosomal recessive |
Medium-chain acyl-CoA dehydrogenase deficiency (MCAD) | most common of fatty acid oxidation disorders, peak symptoms at 4-24 months of age, contributes to SIDS cases, treatment=avoid fasting, avoid medium chain fats |
Glycogen metabolism | defects in making or breaking down glycogen |
Glycogen metabolism: | Nine different diseases caused by various enzyme defects in the glycogen pathway Symptoms arise from inability to utilize glycogen for energy=hypoglycemia; storage of glycogen in cells=toxic to cells |
Mitochondrial metabolism defects | Defect in the respiratory chain pathway; • Variable presentation with variable age of onset |
Mitochondrial metabolism defects | Unable to convert glucose, fat or protein to ATP |
Mitochondrial metabolism defects Inheritance | autosomal recessive or mitochondrial |
Lysosomal storage diseases | Lysosomes are cytoplasmic organelles which have enzymes with phagocytic (degradative) function of macromolecules |
Lysosomal storage diseases | These disorders result in accumulation of macromolecules in target organs (mucopolysaccharides, glycoproteins, various lipids) |
Lysosomal storage diseases | Include the broad categories of disorders= mucopolysaccharidoses, oligosaccharidoses, gangliosidoses (or sphingolipidoses) and related lipid storage diseases |
Lysosomal storage diseases Inheritance | recessive, most autosomal (X-linked - Hunter syndrome, Fabry disease) |
• Lysosomal storage diseases Clinical features | Mostly normal at birth, Regression in development is key finding, All disorders are progressive and most are fatal. |
Lysosomal storage diseases Mucopolysaccharidoses (MPS) | 10 known enzyme deficiencies produce 6 distinct MPS disorders. |
Lysosomal storage diseases Examples | Hurler, Hunter and Sanfilippos syndromes |
Mucopolysaccharidoses (MPS) | share similar clinical features |
Lipid storage diseases Tay-Sachs disease | affecting primarily the CNS; caused by molecular defects, which result in deficiency of Hexosaminidase A in α subunit, on chromosome 15. Results in accumulation of GM2 gangliosides in neurons. |
Tay-Sachs | High incidence in Jewish population, no treatment |
Lipid storage diseases Tay-Sachs disease Clinical features | classic infantile form - normal at birth; onset at 6-12 months; loss of milestones; exaggerated startle response; motor weakness; apathy; cherry red spot in the retina; later onset of seizures, blindness, spasticity and death by age 2-5 years |
Lipid storage diseases Tay-Sachs disease Inheritance | autosomal recessive |
Lipid storage diseases Tay-Sachs disease Diagnosis | enzyme assay; DNA in high risk population ~40- 50% of obligate carriers can be identified by mutation detection |
Lipid storage diseases Tay-Sachs disease Prevention | heterozygote screening by enzyme assay of high risk populations has led to a marked decrease in the disease frequency in those populations |
Steroid Biosynthetic Disorders | Steroid hormone abnormalities, Mineralocorticoid, glucocorticoid, sex steroid pathways interlinked |
Steroid Biosynthetic Disorders Varied effects | ambiguous genitalia to life threatening electrolyte disturbances. |
Steroid Biosynthetic Disorders example | Congenital adrenal hyperplasia, Several forms, 21-hydroxylase (CYP21) deficiency is most common. |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia | expressed in the adrenal cortex, produces cortisol |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia Lab findings | show increases in cortisol precursors, which then flux through other steroid synthetic enzyme pathways, including androgen production. See a decrease in cortisol production |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia affect on males | Males severely affected have salt-wasting variety. Present in adrenal crisis. |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia affect on females | Female severely affected are detected earlier with ambiguous genitalia in addition to cortisol deficiency. |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia Less severe forms | have virilization only, or just signs of mild androgen excess in females. |
Steroid Biosynthetic Disorders example Congenital adrenal hyperplasia Treatment | provide patient with cortisol |
Hypercholesterolemia / hypertriglyceridemia | Lipid disorder |
α1- Antitrypsin | Protein disorder; Liver accumulation of abnormal protein, lung damaged because of deficiency of enzyme action; results in too much protease activity |
Hemachromatosis | metal cofactors; excessive absorption of iron leads to serious overload as an adult. |
Created by:
knpearso
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