Metabolic Disorders Flashcards
Amino Acid Disorders:
- Phenylalanine-Tyrosine Disorders
- Branched-Chain Amino Acid Disorders
- Tryptophan Disorders
- Cystine Disorders
Phenylalanine-Tyrosine Disorders: (4)
- Phenylketonuria
- Tyrosyluria
- Melanuria
- Alkaptonuria
Branched-Chain Amino Acid Disorders: (2)
- Maple Syrup Urine Disease
- Organic Acidemias
Tryptophan Disorders:
- Indicanuria
- 5-Hydroxyindoleacetic Acid
Cystine Disorders
- Cystinuria
- Cystinosis
- Homocystinuria
Amino acid disorders with urinary screening tests: (9)
- Phenylketonuria (PKU)
- Tyrosyluria
- Alkaptonuria
- Melanuria
- Maple syrup urine disease
- Organic acidemias
- Indicanuria
- Cystinuria
- Cystinosis
This type is the result from disruption of a normal metabolic pathway that causes increased plasma concentrations of the nonmetabolized substances
Overflow type
This type is abnormal accumulation caused by malfunctions in the tubular reabsorption mechanism
Renal type
This is referred to as disruption of enzyme function can be caused by failure to inherit the gene to produce a particular enzyme by organ malfunction from disease or toxic reactions
Inborn error of metabolism (IEM)
Where is blood collected for newborn screening test?
Infant’s heel
This is now performed for testing many substances in newborn screening test. It is capable of screening the infant blood sample for specific substances associated with particular IEMs.
tandem mass spectrophotometry (MS/MS)
Metabolic defects cause overproduction of
melanin.
Phenylalanine-Tyrosine Disorders
Most well known of the aminoacidurias
Phenylketonuria (PKU)
PKU is first identified by whom?
Ivan Følling
Urine odor of patient with PKU
Mousy odor
In PKU, these substances are increased
Keto acids, including phenylpyruvate.
Explain why phenylketonuria (PKU) occurs.
This occurs when the normal conversion of phenylalanine to tyrosine is disrupted due to the decreased production of tyrosine and its pigmentation metabolite, melanin. Failure to inherit the gene to produce the enzyme phenylalanine hydroxylase.
used as a follow-up test to ensure proper dietary control in previously diagnosed cases and as a means of monitoring the dietary intake of pregnant women known to lack phenylalanine hydroxylase
Urine testing using ferric chloride
Urine test that is based on the ferric chloride reaction performed by tube test
Urine test for phenylpyruvic acid
Color produced when ferric chloride is added to urine with phenylpyruvic acid
Permanent blue-green color
The accumulation of excess tyrosine in the plasma
Tyrosinemia
Frequently seen metabolic disorder in premature infants caused by underdevelopment of the liver function required to produce the enzymes necessary to complete the tyrosine metabolism
Transitory tyrosinemia
Another form of tyrosine metabolism disorder that is produced from Acquired Severe Liver Disease that resemble the transitory newborn variety but in a more serious condition/
Tyrosyluria
Explain Type 1 Tyrosinemia
Caused by the deficiency
of the enzyme fumarylacetoacetate hydrolase (FAH).
Produces a generalized renal tubular disorder and progressive
liver failure in infants soon after birth.
Explain Type 2 Tyrosinemia
Caused by lack of the enzyme tyrosine aminotransferase.
Persons develop corneal erosion and lesions on the palms, fingers,
and soles of the feet believed to be caused by crystallization of
tyrosine in the cells
Explain Type 3 Tyrosinemia
caused by lack of
the enzyme p-hydroxyphenylpyruvic acid dioxygenase.
This can result in mental retardation if dietary restrictions of phenylalanine and tyrosine are not implemented.
Screening test available for all types of tyrosinemia
Tandem Mass Spectrophotometry (MS/MS)
Urine test used for tyrosyluria
Nitro-naphthol
This results from deficient production of melanin
Albinism
Why is elevated urinary melanin a significant finding?
It indicates proliferation of normal melanin-producing cells which produces malignant melanoma.
Colorless precursor of melanin that is secreted by tumors of malignant melanoma
5,6-dihydroxyindole
the third major defect in the phenylalanine-tyrosine pathway and occurs from failure to inherit the gene to produce the enzyme homogentisic acid oxidase
Alkaptonuria
These disorders can be developed when a person has alkaptonuria
Liver and Cardiac disorders
Caused by an IEM, inherited as an autosomal recessive trait, where failure to inherit the gene for the enzyme necessary to produce oxidative decarboxylation of these keto acids results in their accumulation in the blood and urine
Maple Syrup Urine Disease (MSUD)
Urine screening test for MSUD
2,4-dinitrophenylhydrazine
may be suspected when urine specimens, and sometimes even the patient, possess a characteristic odor of “sweaty feet.”
Isovaleric acidemias
What is the cause of sweaty feet odor in Isovaleric acidemia?
This odor is caused by the accumulation of isovalerylglycine due to a deficiency of isovaleryl coenzyme A in the leucine pathway
Organic acidemias that are detected using MS/MS in newborn screenings
Isovaleric acidemia
Propionic acidemia
Methylmalonic acidemias
a rare inherited disorder, increased amounts of tryptophan are converted to indole.
Hartnup disease
“Blue diaper syndrome”
Hartnup disease
Generalized aminoaciduria
Fanconi syndrome
marked by elevated amounts of the amino acid cystine in the urine
Cystinuria
Presence of increased urinary cystine is due to:
A. Inability of the renal tubules to reabsorb cystine filtered by the glomerulus
B. a defect in the metabolism of cystine
C. Because cystine is much less soluble than the other amino acids
A. Inability of the renal tubules to reabsorb cystine filtered by the glomerulus
Term for increased urinary sugar due to an inherited disorder
Melituria
Indicates the inability to properly metabolize galactose to glucose
Galactosuria
Carbohydrate disorder that is associated with parenteral feeding and pentosuria with ingestion of large amounts of fruit
Fructosuria
Carbohydrate disorder that may be seen during pregnancy and lactation
Lactosuria
A disorder of purine metabolism inherited as a sex-linked recessive results in massive excretion of urinary uric acid crystals
Lesch-Nyhan disease
a group of large compounds located primarily in the connective tissue. They consist of a protein core with numerous polysaccharide branches
Mucopolysaccharides or glycosaminoglycans
Mucopolysaccharide disorders where the skeletal structure is abnormal and there is severe mental retardation
Hurler syndrome and Hunter syndrome
Mucopolysaccharide disorder that is inherited as sex-linked recessive and is rarely seen in females
Hunter syndrome
Mucopolysaccharide disorder where mucopolysaccharides accumulate in the cornea of the eye
Hurler syndrome
Mucopolysaccharide disorder where the only abnormality is mental retardation.
Sanfilippo syndrome
he intermediate compounds in the production of heme
Porphyrins
Collective term for disorders of porphyrin metabolism
Porphyrias
Two screening tests for porphyrinuria
Ehrlich reaction
Fluorescence under UV light (550-600nm)
Screening test for porphyrinuria that is only for the detection of ALA and porphobilinogen
Ehrlich reaction
Screening method for porphyria that does not distinguish among uroporphyrin, coproporphyrin, and protoporphyrin, but it rules out porphobilinogen and ALA.
Fluorescence method
Defects in the metabolism of the amino acid methionine produce an increase in homocysteine throughout the body
Homocystinuria
Cystine disorder that is a defect in the renal tubular transport of amino acids
Cystinuria
Cystine disorder that is an inborn error of metabolism
Cystinosis
Odor of urine of people with cystine disorders
Sulfur
