Disorders of Chemistry Flashcards
Aminoacidopathies
class of inherited errors of metabolism in which there is an enzyme defect that inhibits the body’s ability to metabolize certain amino acids.
Phenylketonuria (PKU)- classic form
Absence of activity of phenylalanine hydroxyls (PAH) due to mutations in PAH gene; newborn concentrations are >1200 umol/L (can be as high as 2.4 mmol/L); other elevated metabolites include phenylpyruvic acid, phenylpyruvate (phenylketone), and phenyl lactic acid; decrease in tyrosine; detected by blood or urine measurements; urine will smell musty or mousy; infants and children exhibit mental retardation and microcephaly; managed by low phenylalanine diet; positive Guthrie test (qualitative); microfluorometric assay of blood spot; HPLC; or LC-MS (Phe/Tyr ratio determined; >1 is PKU)
Phenylketonuria (PKU)- mild form
partial PKU deficiency; PAH concentration between 600-1200 umol/L; treatment by sapropterin dihyrochloride (Kuvan) increases activity of PAH enzyme and low phenylalanine diet.
non-PKU mild Hyperphenylalanimeia
PAH concentrations between 180-600 umol/L; no accompanying accumulation of phenylketones; may be caused by cofactor deficiency (enzymes for BH4 synthesis and regeneration which will also results in deficiency of neurotransmitters from tyrosine and tryptophan (treatment entails supplements of L-DOPA and 5-OH tryptophan)
Tyrosinemia
Inborn metabolic disorder of tyrosine catabolism is characterized by excretion of tyrosine and its catabolites in urine (tyrosinuria). elevated tyrosine in blood by MS/MS; elevated succinylacetone (toxic); treatment is low protein diet and nitisinone
Tyrosinemia-Type I
most severe form; 1 in 100,000 births worldwide; caused by mutation in the FAH gene, which codes for the enzyme fumarylacetoacetate hydrodrolase (FAH), which is the last of 5 enzymes required for metabolism of tyrosine; symptoms manifest in first few months of life; failure to thrive, diarrhea, vomiting, jaundice, a cabbage-like odor, distended abdomen, swelling of legs, and increased predisposition for bleeding; untreated, patients will not live past 10 years old
Tyrosinemia-Type II
1 in 250,000 births worldwide; caused by mutation in TAT gene, which leads to a deficiency of the enzyme tyrosine aminotransferase (TAT), first of the 5 enzymes involved in tyrosine metabolism; half of patients will exhibit impaired mental development; other symptoms include photo sensitivity (photophobia), eye pain and redness, and painful skin lesions on palms and soles of feet
Tyrosinemia-Type III
few cases worldwide (very rare); mutation in HPD gene that results in deficiency of the enzyme 4-hyroxyphenylpyruvate deoxygenate (HPD); second of 5 enzymes involved in tyrosine metabolism; impaired mental development, seizures, and some intermittent loss of balance and coordination;
Alkaptonuria
inherited autosomal recessive disorder; 1 in 250,000 births worldwide; caused by mutation HGD gene; leads to deficiency of the enzyme homogentisate oxidase; elevated levels of homogentisic acid in blood, connective tissues, and urine; symptoms appear in 3rd decade of live (30s); dark-blue/black pigmentation (ochronosis); urine will turn brown/black in color when exposed to air; treatment with Vitamin C;
azotemia
elevated urea in blood
uremia
very high plasma urea concentrations accompanied by renal failure
Prerenal azotemia
result of reduced renal blood flow; less blood is delivered to kidney; consequently, less urea is filtered. elevates plasma urea but plasma creatinine remains normal = high urea N/creatinine ratio
Causative factors of prerenal azotemia
congestive heart failure, shock, hemorrhage, dehydration, and other factors that result in a significant decrease in blood volume; high protein diet and increased protein catabolism (caused by stress, fever, major illness, corticosteroid therapy, and GI hemorrhage)
renal azotemia
result of decreased renal function due to compromised urea excretion;
Causative factors of renal azotemia
acute and chronic renal failure, glomerular nephritis, tubular necrosis,
post renal azotemia
result of obstruction of urine flow at any point in the urinary tract; high urea N/creatinine ratio with elevated creatinine
Causative factors of postrenal azotemia
renal calculi, tumors of the bladder or prostate, or severe infection
decreased urea plasma
low protein intake and severe liver disease; late stage pregnancy and in infancy due to increased protein synthesis; low urea N/creatinine ratio
Glomerular nephritis
type of kidney disease where there is inflammation of the glomeruli (tiny filters that remove excess waste and fluids from the blood); detected by urinalysis (red or white blood cells, infection, or high protein content),
Glomerular nephritis causes
toxins, medicines, viral infections (i.e. hep b or c, HIV), IgA nephropathy, lupus-related kidney inflammation, bacterial infections (strep/staph)
Hyperuricemia
result of overproduction of uric acid, increased metabolism of of cell nuclei; can be exacerbated by a purine rich diet, drugs (chemotherapy), and alcohol;
Lesch-Nyhan
X-linked genetic disorder (males) caused by complete deficiency of hypo-xanthine-guanine phosphoribosyltransferase, an important enzyme in the biosynthesis of purines; results in high plasma and urine concentrations of uric acid
Hyperargininemia
High blood ammonia; normal anion gap; increased arginine and increased orotic acid
Citrullemia
High blood ammonia; normal anion gap; increased citrulline (significant); decreased arginine
Ornithine transcarbamylase deficiency (OTC)
High blood ammonia; normal anion gap; decreased arginine; decreased citrulline, increased glutamine; normal orotic acid
Carbamoylphosphataste synthase I (CPSI) deficiency
High blood ammonia; normal anion gap; decreased citrulline, increased glutamine
Argininosuccinic acidemia (acidula) (ASA)
High blood ammonia; normal anion gap; increased citrulline; decreased arginine; increased argininosuccinic acid in urine
Urea Cycle Disorder
High blood ammonia; normal anion gap
Pyruvate decarboxylase (PC) deficiency
Increased ammonia; high anion gap; with ketosis; increased ammonia; increased lactate; increased pyruvate; increased acetoacetate
Organic Acidemia
Increased ammonia; high anion gap; with ketosis; increased ammonia; normal lactate
Hypoglycemia
decreased glucose
Fatty acid oxidation (FAO) defect
normal plasma ammonia; increased anion gap; no ketosis; increased lactate; hypoglycemia
3-hydroxy-3-methylglutaryl-Co (HMG-CoA) lyase deficiency
normal plasma ammonia; increased anion gap; no ketosis; increased lactate; hypoglycemia; increased leucine; Elevated C5-OH (acylcarnitine)
Normoglycemia
normal glucose
Pyruvate dehydrogenase (PDH) deficiency
normal plasma ammonia; increased anion gap (severe acidosis); no ketosis; increased lactate; normoglycemia; increased alanine in urine
Renal tubular acidosis
normal plasma ammonia; increased anion gap; no ketosis; normal lactate; decreased K+
galactosemia
normal plasma ammonia; normal anion gap; increased galactose; decreased GALT activity
Fructose-1,6-biphosphatase (FBP) deficiency
normal plasma ammonia; high anion gap; with ketosis; increased lactate; hypoglycemia
Glycogen Storage Disease (GSD I -Von Gierke)
normal plasma ammonia; high anion gap; with ketosis; increased lactate; hypoglycemia; enlarged liver
Respiratory Chain Disorder
normal plasma ammonia; high anion gap; with ketosis; increased lactate; hypo or normoglycemia
Adrenal Insufficiency
normal plasma ammonia; high anion gap; with ketosis; normal lactate; hypoglycemia
Maple Syrup Urine Disease (MSUD)
normal plasma ammonia; high anion gap; with ketosis; normal lactate; normoglycemia; maple syrup odor in urine; elevated BCAA (including all-isoleucine); elevated BCKA; elevated leucine/isoleucine; increased 2-OH-isovaleric acid
3-met-crotonyl-CoA carboxylase deficiency
normal glucose, normal ammonia