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Flashcards in Metabolic Disease Deck (33)
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1

overflow

due to increase in plasma levels exceeding the renal threshold
OR
due to increase in urine caused by lack of reabsorption by tubules when plasma levels are elevated (no threshold)

2

renal disorder

due to lack of reabsorption in tubules caused by tubular defects when plasma levels are normal

3

most common abnormalities

overflow disorders ( as opposed to renal)

4

Primary aminoaciduria definition

known as inborn errors of metabolism
inherited defect
2 types
1. enzyme is defective/deficient
2. tubular reabsorption dysfunction

5

secondary aminoaciduria definition

due to other causes such as severe liver disease or generalized renal tubular dysfunction

6

Cystinuria general

inherited autosomal recessive
renal aminoaciduria (!)
defective tubular reabsorption of cystine, arginine, lysine & ornithine

7

clinical signs of cystinuria

formation of calculi & cystine stones - because cystine is less soluble than the other amino acids that are not reabsorbed

8

ways to avoid stone formation

staying well hydrated & D-penicillamine

9

Screening tests for Cystinuria

cystine crystals (!!!) in the urine
cyanide-nitroprusside test= red-purple (!)

10

Cystinosis general

inborn error of metabolism- recessive
intracellular deposition of cystine in lysosomes of all body cells, especially in kidney, eye, bone marrow & spleen
2ndary effect on proximal renal tubule- cystine crystals accumulate in PT= fanconi's syndrome develops

11

clinical symptoms of cystinosis

growth retardation, ricketts, acidosis, polydipsia, polyuria
severe cases = renal failure

12

treatment for cystinosis

renal dialysis
cystine-depleting medications
transplant
if not treated, most patients die by 10 years of age due to renal damage

13

screening tests for cystinosis

cyanide-nitroprusside test= red-purple (!)
clinitest - orange-red

14

Homocystinuria general

lack enzyme cystathione synthase= converts homocysteine to cystathione which is needed for brain development

15

screening tests for homocystinuria

cyanide-nitroprusside= positive
silver nitroprusside test - only homocystine will react (not cystine)

16

Maple Syrup urine disease

rare, inherited, autosomal recessive
accumulation of branched-chain amino acids - leucine, isoleucine & valine
defect or deficiency in enzyme responsible for normal oxidative decarb to acyl-CoA derivatives

17

newborn symptoms of maple syrup urine disease

acute ketoacidosis
vomiting
seizures
lethargy
urine has distinctive maple syrup odor due to rapid accumulation of ketoacids

18

screening test for maple syrup urine disease

2,4-dinitropenylhydrazine (DNPH)= yellow
ferric chloride = green-gray
diagnosis is made by amino acid analysis using MS/MS

19

Phenylketonuria general

inherited, autosomal recessive
deficient/defective phenylalanine hydroxylase
results in buildup of phenylketones in serum & urine

20

clinical symptoms of phenylketonuria

delayed development & feeding difficulties
'mousy' or 'musty' odor of urine (!!)
decreased skin pigmentation (!!)
increased plasma levels of phenylalanine leads to brain injury /mental retardation

21

screening test for phenylketonuria

guthrie microbial inhibition test (blood)-if phenylalanine is increased it will counteract the action of the inhibitor in the test & the microbes will grow
ferric chloride test= green-gray

22

Alkaptonuria general

rare, recessive disease
deficient/defective enzyme homogentisic acid oxidase causing a buildup of homogentisic acid

23

clinical symptoms of alkaptonuria

ochronosis- abnormal dark blue or black tissue pigmentation
degenerative arthritis
urine darkens after becoming alkaline (!!)

24

screening test for alkaptonuria

ammonical silver nitrate- black color
benedict's test- yellow precipitate
ferric chloride- transient deep blude
confirmatory- TLC or HPLC

25

Tyrosinuria causes

several causes:
transient-immature liver
acquired severe liver disease
hereditary disorder: no enzymes are produced; usually fatal

26

lab findings of tyrosinuria

tyrosine & leucine crystals
'cabbage-like' odor to urine (!!)

27

screening test for tyrosinuira

nitrosonaphthol test - non specific for urine
ferric chloride- transient green

28

Melanuria general

increased melanin due to a malignant melanoma
urine darkens when exposed to air or sunlight (!!)

29

melanuria screening test

must be differentiated from alkaptonuria (also turns black)
ferric chloride- gray or black precipitate (!)
sodium nitroprusside- red
ehrlich's reagent- red

30

Galactosuria general

inherited autosomal recessive defect in CHO metabolism
deficiency- galactose-1-phosphate uridyl transferase
galactose cannot be converted to glucose