CMB Exam 2 - Diseases Flashcards
Tyrosinemias Type II and III
More benign than type I, because blockage happens earlier in the pathway and succinylacetone is not produced. May result in keratitis (severe visual disturbances) and hyperkeratosis of palms and soles. Treatment with a restricted phenylalanine/tyrosine diet is effective.
classic galactosemia
Due to loss of uridylyltransferase (GALT). Typically presents in the first weeks after birth; presents with poor feeding, weight loss, vomiting, diarrhea, lethragy; hepatomagaly, jaundice, and bleeding disorders; renal tubule disease; can lead to blindness. SSx resolve upon galactose restriction.
Cystinuria: treatment
Penicillamine and other compounds increase the solubility of cystine by complexing with it.
Tyrosinemia Type I: screening and diagnosis
After an abnormal neonatal screen, check quantitative plasma tyrosine and blood/urine succinylacetone. Diagnosis is confirmed by increased concentration of succinylacetone. Some DNA testing is available as well.
ASL deficiency: diagnosis
Elevated citrulline in screen, elevated argininosuccinate in the urine.
type VI glycogenosis
(Hers disease; liver phosphorylase deficiency) Hepatic-hypoglycemic glycogen storage disease, ketonuria. Probably good prognosis.
Mutations in which genes cause neonatal diabetes mellitus?
KCNJ11 and ABCC8 (subunits of the ATP-sensitive potassium channel) and others.
type IV glycogenosis
(Andersen disease; branching enzyme deficiency) Presents with hepatic cirrhosis and early liver failure, but doesn’t directly affect blood glucose levels. Prognosis is usually death within the first year.
hyperkeratosis
Abnormal thickening of the skin. Can result from tyrosinemia types II and III.
plasma acylcarnitine profile
Excessive intermediates of fatty acid oxidation and organic acid catabolism are conjugated with carnitine, so the plasma acylcarnitine profile reflects this accumulation.
essential fructosuria
Benign condition resulting from a deficiency of fructokinase. Characterized by hyperfructosemia and fructosuria.
Andersen disease
Type IV glycogenosis; branching enzyme deficiency. Presents with hepatic cirrhosis and early liver failure, but doesn’t directly affect blood glucose levels. Prognosis is usually death within the first year.
Tyrosinemia Type I: SSx
Accumulated liver metabolites, bleeding disorder, hypoglycemia, hypoalbuminemia, elevated transaminases, and defects in renal tubular function. May cause hepatocellular carcinoma.
What effect can cystic fibrosis have on protein metabolism? What is the treatment?
Defective chloride channels cause inspissations of pancreatic exocrine secretion, obstructing enzyme release. Treatment is supplementation of pancreatic enzymes with each meal.
galactosemia
Due to loss of galactokinase (GALK). Can result in cataracts and/or blindness. SSx resolve upon galactose restriction.
OTC deficiency: inheritance
X-linked.
Which of the glycogenoses is predominantly hepatic-hypoglycemic?
Types I (Ia - von Gierke disease - and Ib), VI (Hers disease), and VIII. Type III (Forbes disease) does muscle AND liver. These patients tend to present with hepatomagaly and hypoglycemia.
OTC deficiency: SSx
High neonatal mortality in males. In females, SSx can include hyperammonemia, recurrent emesis, lethargy, seizures, developmental delay, and episodic confusion. They may spontaneously limit protein intake.
type II glycogenosis
(Pompe disease; lysosomal α-glucosidase deficiency) Myopathic. Presents with cardiomegaly, symmetrical muscle weakness, heart failure, and a shortened P-R interval. Prognosis is usually death in first year; enzyme therapy is available but expensive.
metabolic alkalosis
Increase in blood HCO3- (eg vomit out your acid, exogenous bicarb/antacids, respiratory compensation (hypoventilation increases both H+ and HCO3-). Resulant hypokalemia can depolarize neurons.
MSUD: enzyme deficiency
(branched chain ketoaciduria) A deficiency of the decarboxylase initiates the degradation of the ketoacid analogs of the three branched chain amino acids—leucine, isoleucine, and valine.
What qualify as elevated glucose levels?
> 126 mg/dL fasting, >200mg/dL post-prandial (especially on 2 occasions, 2 hours after 75g dose of glucose (OGTT)
metabolic acidosis
Usually caused by influx of (exogenous) organic acid. HCO3- tends to drop.
epimerase deficiency
(GALE) 1 of 3 kinds of galactose intolerance. Has 2 forms: the benign one is in erythrocytes, the severe looks like GALT deficiency (ie GI issues, liver issues, kidney issues, potential blindness).
Lesch-Nyhan syndrome
X-linked recessive HGPRT deficiency; results in build-up of PRPP and uric acid (and increased de novo purine synthesis), and decreased levels of AMP and GMP. Characterized by neurological features like self-mutilation and involuntary movements/grimacing.
Beriberi: SSx
Thiamin deficiency. SSx include diarrhea and liver disease. Early stage symptoms sinclude fatigue, irritability, poor memory, sleep distrubances, chest pain, anorexia, abdominal pain, constipation. Common in alcoholics and in non-varied diets like white rice.
gout
Caused by excess uric acid, which precipitate in the joints. Can be due to HGPRT deficiency or glucose-6-phosphatase deficiency (decreases gluconeogenesis, which increases pentose phosphate pathway, which increases ribose-5-phosphate, which increases PRPP, which increases purine synthesis) . Also related to lead contaminants in alcohol (lead causes kidney damage and decreased excretion of uric acid in urine) or excessive sugary beverages.
phenylalanine hydroxylase
Converts phenylalanine into tyrosine. Deficiency = Phenylketonuria; hyperphenyalaninemia.
favism
Hemolytic anemia; can be induced by a variety of oxidative agents (infection, drugs, fava beans); all victims are G6PDH deficient. SSx: anemia, elevated bilirubin,dark urine.
type VII glycogenosis
(Tarui disease; muscle phosphofructokinase deficiency) Muscle fatigue beginning in adolescence. Good prognosis with sedentary lifestyle.
chronic granulomatous disease
Deficiency in G6PDH (
Which metabolic disorder is autosomal dominant?
Familial hypercholersterolemia
type 1b glycogenosis
(Glucose-6-phosphate translocase deficiency) Similar presentation as type Ia (hepatomegaly, hypoglycemia, lactic acidosis, ketosis, bleeding, gout, hypertriglyceridemia, xanthomas) but with neutropenia and GI dysfunction. Risk of hepatomas or death from hypoglycemia, plus risk of infection.
maternal PKU
75%-90% of children born to adult PKU females with hyperphenylalaninemia are mentally retarded and microcephalic, 15% have congenital heart disease. Caused by excess prenatal phenylalanine.
MSUD: SSx
(branched chain ketoaciduria) Within 1-4 weeks: poor feeding, vomiting, tachypnea, CNS depression and EXTENSOR SPASMS, opisthotonos, seizures. Urine has odor of maple syrup. Lab manifestations: hypoglycemia, metabolic acidosis (ketone bodies and branched-chain acids) with elevation of undetermined anions.
“gallop” heart rhythm
Consistent with heart failure. Can present with many conditions including Pompe disease.
PKU: enzyme deficiency
Phenylalanine hydroxylase; 2% of cases are BH4 abnormalities, which CANNOT be treated by restriction of phenylalanine.
respiratory acidosis
Caused by compromised ventilation, over-production or increased intake of CO2.
What is the clinical consequence of ornithine deficiency?
Hyperammonemia and elevated urine orotate (since the backed-up carbamoyl phosphate is converted to orotic acid).
MSUD: treatment
(branched chain ketoaciduria) Provision of adequate calories with restriction of leucine; hemodialysis/hemofiltration/peritoneal dialysis if in acidotic crisis; monitor for cerebral edema. Liver transplantation effectively treats MSUD.
McArdle disease
Type V glycogenosis; muscle phosphorylase deficiency. Presents with muscle fatigue beginning in adolescence (similar to type VII, Tarui disease). Good prognosis with sedentary lifestyle.
PKU: treatment
Immediate, strict restriction of phenylalanine. Restriction within 10 days of birth can allow normal cognitive function. Tyrosine becomes essential.
What are the 3 components of “ketone bodies”?
Acetone, acetoacetate, and hydroxybutyrate. Only acetone is a ketone, the other two are acids.
What is the treatment for “transient tyrosinemia of the newborn”?
Ascorbic acid.
hereditary fructose intolerance
Severe autosomal recessive defect in aldolase B. Treatment is immediate removal of fructose from the diet.
gestational diabetes
Human placental lactogen has anti-insulin action and reduces insulin sensitivity. Develops in ~7% of pregnancies.
type V glycogenosis
(McArdle disease; muscle phosphorylase deficiency) Presents with muscle fatigue beginning in adolescence (similar to type VII, Tarui disease). Good prognosis with sedentary lifestyle.
Altered transport of which AAs has been implicated in schizophrenia and bipolar disorder? Why?
Tyrosine and tryptophan; these are precursors for dopamine and serotonin.
respiratory alkalosis
Hyperventilation, breathe off too much CO2. Resulant hypokalemia can depolarize neurons.
LADA
(latent autoimmune diabetes in adults) slow autoimmune destruction of
Hartnup syndrome
Impaired transport of tryptophan; results in pellagra-like symptoms (dermatitis, diarrhea, dementia). Treatment with tryptophan is successful.
What happens to an individual if their glucokinase has a higher Km?
Glucokinase’s velocity would decrease, decreasing the pancreas’ release of insulin and elevating normal fasting blood glucose levels.
An increase in guanidinoacetic acid reflects a disorder of…
creatine biosynthesis.
Tyrosinemia Type I: enzyme deficiency
Due to fumarylacetoacetate hydrolase deficiency (causes liver disease)
What anion becomes elevated when ethylene glycol (antifreeze) is ingested?
Glycolate (Ca++, oxalate crystals)
Homocystinuria: enzyme defect
Deficiency of cystathionine β-synthase (normally converts homocysteine to cysteine); causes buildup of homocysteine, which is reconverted to methionine.
Kwashiorkor syndrome
Caused by dietary protein deficiency, leading to albumin deficiency (among other things). Characterized by fluid leakage into abdomen: distended abdomen.
hypokalemia
Low K+ in the plasma. Can result from acute alkalosis (H+ leaves the cell, driving K+ in).
Which metabolic disorder is x-linked?
Ornithine Carbamoyl Transferase deficiency
urine acylglycine profile
Excessive intermediates of fatty acid oxidation and organic acid catabolism are conjugated with glycine, so the urine acylglycine profile reflects this accumulation.
G6PDH deficiency
X-linked recessive. RBC most affected (lots of oxidative stress). Common in areas with endemic malaria.
Homocystinuria: treatment
Homocysteine restricted diet with cystine and folate supplementation (since folate is trapped in the process of remethylation of homocysteine to methionine). Some forms respond to pyridoxine therapy, and the others need betaine to help with methylation.
What anion becomes elevated in ketoacidosis?
β-OH butyrate, acetoacetate
keratitis
Results in sever visual disturbance. Can result from tyrosinemia types II and III.
kernicterus
Neonatal G6PDH deficiency elevates bilirubin, which can accumulate in grey matter. Treatment includes bili-lights.
cystinuria
Patients inherit defective transport of cystine (sulfide-linked cysteines) and basic AAs (lysine, arginine, ornithine) across the brush-border membranes of intestinal and renal cells. Cystine isn’t very soluble so it can then form kidney stones.
MSUD: inheritance, incidence
(branched chain ketoaciduria) Autosomal recessive; 1:250,000 live births
tetrahydrobiopterin
Cofactor for phenylalanine hydroxylase. Deficiency leads to a malignant form of PKU that can’t be treated by restriction of dietary phenylalanine.
What are the major complications of diabetes?
Infections, retinopathy, neuropathy, nephropathy, heart disease % stroke, impotence, and ketoacidosis (Type I)
Pompe disease
Type II glycogenosis; lysosomal α-glucosidase. Myopathic. Presents with cardiomegaly, symmetrical muscle weakness, heart failure, and a shortened P-R interval. Prognosis is usually death in first year, but gene therapy looks promising.
PKU: presentation/progression
Affected infants are normal at birth but soon develop rising plasma phenylalanine, impairing brain deveopment. Severe mental retardation is evident by 6 months. Other SSx include seizures, hypopigmentation (since tyrosine is a precursor of melanin), and eczema, musty or mousy-smelling urine (from shunting biproducts).
PKU: prevalence, inheritance
1:10,000 births; autosomal recessive; common in people of Scandanavian descent (tend to be blond), uncommon in Jewish and black populations
“Abnormal Newborn State Screen”
Screens are for anticipatory education and early intervention.
Which of the glycogenoses is predominantly myopathic?
Types V (McArdle disease) and VII. Type III does muscle AND liver. This tend to manifest with muscle cramps after exercise and a lack of lactase (due to blocked glycolysis).
Hartnup disease
Patients inherit defective transport of neutral AAs across intestinal and renal epithelial cells. This results in deficiency of essential amino acids, which in part causes failure to thrive, photosensitivity, and tremors.
OTC deficiency: diagnosis
Plasma AA profile may show low citrulline and arginine, with high glutamate and alanine. Urine organic acid profile after protein loading shows orotic acid. DNA testing is also available.
Which of the glycogenoses affect miscellaneous tissues? What do their deficient enzymes have in common?
Types II (Pompe disease) and IV (Andersen disease). They lead to glycogen build-up in many organs, but cardiomegaly is the most prominent feature.
severe combined immunodeficiency (SCID)
(Adenosine deaminase deficiency) Presents within first month of life; patients lack both T cell and B cell immunity. Treatment involves bone marrow transplant.
type III glycogenosis
(Forbes disease; debranching enzyme deficiency) Affects both muscles and liver. Presents with hepatomegaly (that resolves with age), hypoglycemia, ketonuria, and may show muscle fatigue. Ok prognosis.
type VIII glycogenosis
(Phosphorylase kinasae deficiency) Hepatic-hypoglycemic glycogen storage disease.
nitisinone
Indicated for tyrosinemia type I; inhibits oxidation of toxic accumulation of liver metabolites.
What anion becomes elevated when methanol is ingested?
Formic acid
von Gierke disease
Type 1a glycogenosis; glucose-6-phosphatase deficiency. Hepatic-hypoglycemic glycogen storage disease. SSx: chuccy cheeks, hypoglycemia, lactic acidosis/ketosis, hepatomegaly, hypotonia, slow growth, bleeding, diarrhea, gout, hypertriglyceridemia, xanthomas. If untreated with dietary therapy, can result in early death from hypoglycemia, or hepatomas in later childhood.
What anion becomes elevated when paraldehyde is ingested?
Acetaldehyde, acetate
Tarui disease
Type VII glycogenosis; muscle phosphofructokinase deficiency. Muscle fatigue beginning in adolescence. Good prognosis with sedentary lifestyle.
type 1a glycogenosis
(von Gierke disease; glucose-6-phosphatase deficiency) Hepatic-hypoglycemic glycogen storage disease. SSx: chubby cheeks, hypoglycemia, lactic acidosis/ketosis, hepatomegaly, hypotonia, slow growth, bleeding, diarrhea, gout, hypertriglyceridemia, xanthomas. If untreated with dietary therapy, can result in early death from hypoglycemia, or hepatomas in later childhood.
Tyrosinemia Type I: treatment
Nitisinone (an inhibitor of the oxidation of liver metabolites?) and restricted dietary phenylaline and tyrosine.
What anion becomes elevated when excess aspirin is ingested? (complicated)
Salicylate and lactate
MSUD: diagnosis
(branched chain ketoaciduria) Large increases in plasma leucine, isoleucine, and valine concentrations and identification of alloisoleucine in the plasma in excess.
“Metabolic Syndrome”
Characterized by central obesity (“apple shape”). Fructose increases risk of this.
OTC deficiency: treatemt
Treatment for hyperammonemia; hemodialysis; liver transplantation (especially in males).
hyperammonemia: treatment
Reduced protein intake; IV glucose (to slow catabolism); alternate pathway agents (eg sodium benzoate, sodium phenylacetate); arginine supplementation. In some cases, liver transplantation may be necessary.
Beriberi: biochemistry
Thiamin deficiency inhibits pyruvate dehydrogenase. Accumulation of pyruvate, lactate, citrate, and α-ketoglutarate. Reduces actylcholine synthesis (acetyl-CoA is a precursor).
Hers disease
Type VI glycogenosis; liver phosphorylase deficiency. Hepatic-hypoglycemic glycogen storage disease, ketonuria. Probably good prognosis.
hyperkalemia
Excess K+ in the blood. Can result from acute acidosis or from quick correction of chronic alkalosis.
What anion becomes elevated in lactic acidosis? (hypoxemia, ischemia)
Lactic acid
Homocystinuria: SSx
Elevated blood/urine homocysteine and blood methionine. Produces a clinical syndrome that includes dislocated ocular lenses; long, slender extremities; malar flushing; livedo reticularis; skeletal features; mental retardation and/or psychiatric illness. Major thromboses are a risk.
ELMPARK (acid-base imbalances)
Ethylene glycol (glycolate; Ca++, oxalate crystals); Lactic acidosis (lactic acid); Methanol (paraldehyde); Aspirin (salicylate and lactate); Renal tubular acidosis (sulfate & phosphate; NORMAL anion gap acidosis), uremia (inability to excrete NH4+; end-stage renal disease); Ketoacidosis (β-OH butyrate, acetoacetate).
Forbes disease
Type III glycogenosis; debranching enzyme deficiency. Affects both muscles and liver. Presents with hepatomegaly (that resolves with age), hypoglycemia, ketonuria, and may show muscle fatigue. Ok prognosis.
Homocystinuria: inheritance, prevalence
Autosomal recessive; 1:200,000 live births
Munchausen syndrome by proxy
Munchausen is the psychological need to have/invent symptoms. “By proxy” refers to a parent’s need to do so for a child.
tophi
Precipitates of uric acid in gout
What are the complications of diabetic ketoacidosis?
Hyperglycemia, vomiting, dehydration, kussmaul breathing, confusion, coma (~600 mg/dL, extremem dehydration). Treatment is insulin and rehydration + electrolytes.
PKU: screening and diagnosis
Only blood levels of phenylalanine can differentiate benign hyperphenylalaninemia (>360uM) from malignant PKU (>600uM). 5x the normal level of phenylaline = malignant. WThen we can screen to identify PAH mutations (there are at least 500, but only some are malignant).
Which urea cycle enzyme deficiency does NOT cause symptomatic UCD? What are its consequences?
Arginase: causes moderate blood ammonia, high arginine, low citrulline, and low orotate.
What mutations are associated with MODY?
Glucokinase. Mutations shift the Km higher.
Homocystinuria: diagnosis
Elevated total homocysteine in the blood. Hypermethioninemia. Some genetic testing is available.
What anion becomes elevated in renal tubular acidosis (NORMAL anion gap acidosis)?
Sulfate, phosphate
