Metabolic Disorders Flashcards
Which disorders does the Guthrie blood spot test screen for?
Phenylketonuria, congenital hypothyroidism, cystic fibrosis, sickle cell disease, medium chain acyl-co-A dehydrogenase deficiency, maple syrup urine disease, isovaleric acidaemia, glutaric aciduria type 1, homocystinuria
What is phenylketonuria?
Phenylalanine hydroxylase deficiency
What is congenital hypothyroidism?
Dysgenesis or agenesis of the thyroid gland
What is specificity?
The probability that someone without the disease will correctly test negative
What is sensitivity?
The probability that someone with the disease will correctly test positive
What is positive predictive value?
The probability that someone who tests positive actually has the disease
What is negative predictive value?
The probability that someone who tests negative actually doesn’t have the disease
Name an organic acidaemia
Propionic acidaemia, isovaleric acidaemia
Describe the key clinical features of organic acidaemias
High urea and ketones, metabolic acidosis. May have a funny smell from organic acids
How are organic acidaemias managed?
Low protein diet, acylcarnitine, and haemofiltration
Name one of the nine urea cycle disorders
Ornithine transcarbamylase deficiency
Describe the key clinical features of urea cycle disorders
High ammonia (>200uM) leading to encephalopathy and developmental delay. Respiratory alkalosis. Vomiting
How are urea cycle disorders managed?
Low protein diet to stop urea formation
Name two amino acidopathies
Maple syrup urine disease, phenylketonuria
Describe the key clinical features of phenylketonuria
High phenylalanine, blue eyes, fair hair and skin, retardation
Describe the key clinical features of glycogen storage disorders
Hypoglycaemia, lactic acidosis, hepatomegaly, developmental delay. High risk of hepatoblastoma
Describe the key clinical features of galactosaemia
Cataracts, hypoglycaemia, neonatal conjugated jaundice
How is galactosaemia managed?
Low lactose and galactose diet
Name a fatty acid oxidation disorder
Medium chain acyl CoA dehydrogenase deficiency (MCADD)
Describe the clinical features of MCADD
Hypoglycaemia, cardiomyopathy, rhabdomyolysis, low ketones
How is MCADD screened for?
Blood acylcarnitine
How is MCADD managed?
Regular carbohydrate
What are the clinical features of peroxisomal disorders?
Poor feeding, seizures, retinopathy, hepatomegaly, mixed hyperbilirubinaemia
What are the clinical features of glycosylation disorders?
Retardation, nipple inversion
How are glycosylation disorders diagnosed?
Measure serum transferrins
Name a lysosomal disorder
Tay Sachs disease
Describe the clinical features of lysosomal disorders
Very slow progressing neuroregression, hepatosplenomegaly, cardiomyopathy
How are lysosomal disorders diagnosed?
Urine mucooligopolysaccharides, WBC enzyme levels
How are mitochondrial disorders diagnosed?
Muscle biopsy
Describe the blood test results in mitochondrial disorders
High lactate and creatine kinase
State three groups of metabolic disorders that lead to accumulation of toxins
Organic acidaemias, urea cycle disorders, aminoacidopathies
State three groups of metabolic disorders that lead to reduced energy stores
Glycogen storage disorders, galactosaemia, fatty acid oxidation disorders
State two groups of metabolic disorders that affect large molecule synthesis
Peroxisomal disorders, glycosylation disorders
What are peroxisomal disorders?
Inability to catabolise very long fatty acids or produce bile acids
