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27 Cards in this Set
- Front
- Back
Metabolic disorders
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Renal type:
-caused by malfunction in tubular reabsorption Overflow type: -caused by disruption of a normal metabolic pathway: -result is increased plasma concentrations of nonmetabolized substances |
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Metabolic disorders
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Most metabolic disorders occur from protein, fat, CHO metabolism
-disruption of enzyme function -lack of enzyme production: lack gene, this is known as an inborn error of metabolism (IEM) -disease which causes organ malfunction -toxic reactions Now we do newborn screenings for IEM: heel stick |
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Amino Acid Disorders:
Phenylalanine-Tyrosine Disorders Phenylketonuria (PKU) |
-an aminoaciduria, 1/10,000-20,000 births
-can lead to mental retardation -gives mousy odor to urine |
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Phenylketonuria (PKU)
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-urine contains increased amounts of ketoacids such as phenylpyruvate
-failure to inherit gene that produces enzyme phenylalanine hydroxylase -restrict diet, alternate pathways for phenylalanine metabolism will develop -first test, Guthrie- a microbial inhibition assay |
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Phenylketonuria (PKU)
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-cutoff is 2 mg/dl
-urine as follow up testing, monitoring diet in at risk pregnant women -screening: ferric chloride reaction tube test for phenylpyruvic acid |
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Tyrosyluria
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-tyrosinemia results is tyrosine in urine
-includes tyrosine and its degradation products -causes can be metabolic or inherited -can result in liver and tubular disease -3 types |
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Tyrosyluria
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-Type 1: generalized tubular disorder and progressive liver failure soon after birth
-Type 2: corneal erosion, lesions on palms, fingers, soles of feet -Type 3: mental retardation of diet is not restricted -screening: nitroso-naphthol tube test |
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Melanuria
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-results from disruption in the second metabolic pathway of tyrosine
-affects production of melanin, thyroxine, epinephrine and others: albinism from lack of pigment melanin -urine turns dark when exposed to air -overproduction of melanocytes causes melanomas which secrete a precursor of melanin -tests: ferric chloride, Na nitroprusside, Ehrlich’s |
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Alkaptonuria
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urine turns dark from becoming alkaline from standing at room temp
-lacks enzyme homogentisic acid oxidase -no completion of pathway: homogentisic acid accumulates in blood, tissues and urine -brown stained or red colored diapers -brown stains deposit in tissues- liver and cardiac disorders |
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Alkaptonuria
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-tests: *ferric chloride, Clinitest, add alkali to freshly voided urine, silver nitrate and NH4OH, spectrophotometric
-distinguish between melanin and homogentisic acid |
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Branched-Chain Amino Acids Disorders
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Contain a methyl group that braches from the main aliphatic
-accumulation of one or more early degradation products -accumulation of organic acids further down the metabolic pathway: organic acidemias |
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Maple Syrup Urine Disease (MSUD)
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a rare IEM, involving leucine, isoleucine, valine
-beginning of pathway is normal- ketoacids produced -lack enzyme for decarboxylation of ketoacids- build up in blood and urine -infants have failure to thrive and maple syrup odor to urine: early detection to prevent mental retardation and death -restrict diet, monitor urinary ketoacids |
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Maple Syrup Urine Disease (MSUD)
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included in newborn screening tests
-test: 2,4-dinitrophenylhydrazine (DNPH) reaction- adding to positive urine makes yellow precipitate -on multistix/ chemstrips? |
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Organic Acidemias
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-includes isovaleric, propionic, methylmalonic acidemia
-cause severe illness: vomiting, hypoglycemia, ketonuria, elevated serum ammonia levels -Isovaleric acidemia: urine and patients have sweat feet odor: lack enzyme isovaleryl coenzyme A in the leucine pathway -need MS/MS methodology for newborn screen -no other tests |
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Tryptophan Disorders
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characterized by increased urinary excretion of 5-hydroxyindolacetic acid (5-HIAA) and indican
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Indicanuria
Tryptophan Disorders |
-caused by intestinal obstruction
-tryptophan converted to indole |
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5-HIAA
Tryptophan Disorders |
-a degradation product of serotonin
-accumulations of 5-HIAA are caused by tumors -use random or first morning specimens -consider diet before testing |
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Cystine Disorders
Cystinuria |
-a defect in renal transport of amino acids
-tubules can’t reabsorb cystine filtered by the glomerulus -can involve cystine, lysine, ornithine, arginine -form renal calculi at young age -in UA: crystals -test: sodium nitroprusside |
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Cystinosis
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-an IEM causing a sulfur odor to urine
-nephropathic: membrane defects prevent release of cystine into cytoplasm for metabolism: causes cystine deposits in the body (cornea, bone marrow, lymph nodes, organs)—can progress to renal failure -nonnephropathic: benign- some ocular involvement |
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Homocystinuria
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-defective metabolism of methionine causes accumulation oh homocystine in the body
-failure to thrive, mental retardation, thomboembolic disorders, cataracts, death -early screen, confirm with silver-nitroprusside |
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Porphyrin Disorders
Porphyrins |
Intermediate compounds in heme production
Disorders are called porphyrias 3 primary porphyrins and 2 precursors -precursors ά-aminolevulinic acid (ALA) and porphobilinogen Blockage of heme synthesis can occur at several points: accumulation of product formed just before the interruption |
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Porphyrins
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Can check urine, blood, stool, bile
Porphyrias can be inherited or acquired -lead poisoning, iron deficiency, exposure to toxins, chronic renal or liver disease -lack of gene for enzyme production are inherited -urine may have a red or port wine color when exposed to air, stained teeth and diapers -tests: Ehrlich’s and fluorescence |
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Mucopolysaccharide Disorders
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Mucopolysaccharides
AKA glycosaminoglycans Large compounds located in connective tissue Defective metabolism of polysaccharide potion of the molecule causes accumulation in lysosomes of connective tissue 3 substrates can accumulate- need to identify specific enzyme |
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Mucopolysaccharide Disorders
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Mucopolysaccharide con’t
Diseases -Hurler’s Disease: accumulation in corneas -Hunter’s Disease: rare in females -for both: abnormal skeletal structure and mental retardation -Sanfilippo Syndrome: mental retardation -tests: turbidity and metachromatic spot staining |
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Purine Disorders
Lesch-Nyhan Disease |
-lack of enzyme causes accumulation of uric acid throughout the body
-causes gout, renal calculi, motor defects, mental retardation -in UA: uric acid |
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Carbohydrate Disorders
Melituria |
Increased in urinary sugar, inherited
Clinitest positive for reducing substances, while chemstrip glucose oxidase is negative Clinitest detects reducing substances: copper reduction test Melituria includes galactosuria, lactosuria, fructosuria |
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Carbohydrate Disorders
Galactosuria |
-inability to metabolize galactose to glucose: accumulation of galactose and toxic intermediates in the blood
-cause by deficiency of 1 or 3 enzymes -GALT (galactose-1-phosphate uridyl transferase) deficiency leads to severe mental retardation and liver disorders -part of newborn screening |