Metabolic Flashcards
How do you calculate anion gap and what is normal?
([NA+] + [K+]) - ([HCO3-] + [CL-])
Normal is 10-14
What are the causes of metabolic acidosis with rasied anion gap?
Lactic acidosis
DKA
Poisoning with: salicylate, methanol, propylene glycol, iron, isoniazid, ethylene glycol
Renal failure
Acid producing metabolic disorders
What are the causes of metabolic acidosis with normal anion gap?
Renal tubular acidosis
Addison’s disease
Acetozolamide use
Severe diarrhoea
Post-ureteric diversion into large bowel
What are normal ammonia levels in neonates and children?
<100 µmol/L in neonates and <50 µmol/L thereafter
What is the classic presentation of a urea cycle disorder?
Poor feeding, seizures and reduced GCS in 1-5 days of life
What are the classic lab findings for urea cycle diorder?
+++ ammonia, high lactate
respiratory alkalosis (driven by ammonia)
plasma amino acids deranged
How are urea cycle disorders inherited?
AR
Except OTC which is X-linked
Urea cycle orders are differentiated according to which amino acids are deranged. What are the two commonest types (in exams) + what amino acids are raised?
OTC - high alanine glutamine, low araganine and citrulline. V high urine orthotic acid
Citrullinaemia- high alanine and glutamine, very high citrulline. Low ariginine urine othotic acid
Citrullinaemia has what enzyme defect?
ASS
What is the management for Urea cycle disorders?
Acute: NBM, 10% dextrose +electroyltes. Sodium benzoate + haemofiltration.
Lifelong low protein diet + ammonia scanvengers
Define hypoglycaemia
A true blood glucose of <2.6 mmol/L.
What presentation would make you think of glycogen storage disease 1 ?
Hypoglycaemia, raised lactate
hepatomegally
Describe how glycogen storage disease 1 leads to hypoglycaemia
Deficiency of glucose-6-phosphatase therefore inability to mobilize glucose from glycogen or to utilize glucose from gluconeogenesis.
Describe Glycogen storage disease V
deficiency of the myophosphorylase enzyme, which leads to reduced glycolysis in muscle fibres and reduced production of pyruvate.
Describe Glycogen storage disease V present?
muscle pain and cramps and fatigue during brief, intense exercise a/w episodes of dark urine (myoglobin)
Describe Leigh’s syndrome
Mitochondrial disease
Sub-acute sclerosing encephalopathy
Presented as 2-3 yr old with developmental delay/ seizure/ myopathy
Raised lactate and classic MRI findings
What are the MRI findings for Leigh’s syndrome?
Symmetrical changes of the basal ganglia and the brainstem.
How does MCAAD present?
Part of neonatal screening
Can present before with poor feeding, generally unwell and seizures and Hypoketotic hypoglycaemia.
What is MCAAD a disorder of?
fatty acid oxidisation disorder
(Medium-chain acyl-CoA dehydrogenase )
How is MCAAD diagnosed?
clinical picture + measurement of carnitine and acylcarnitine levels and urine organic acids
What is treatment of MCAAD?
Avoid prolonged fasting and take extra calories when ill
Will otherwise have normal development and growth
Describe idiopathic ketotic hypoglycaemia
Presenting in first few years with hypoglycaemia and ketones during intercurrent illness or prolonged fast. Treat with emergency glucose and avoid fasting.
resolves by 8 years of age
Diagnosis of exclusion - need all your ammino acids plasma and urinary and carntitne and acylcarnitine to be normal
What are the lab findings of Galactosaemia?
Conjugated bilirubinaemia , deranged coag and metabolic acidosis, urinary reducing substances, glycosuria, aminoaciduria, albuminuria.
Describe Galactosaemia, it’s mode of inheritance and how it usually presents
AR
Cannot metabolise galactose
Presents as jaundice, poor feeding, cataracts, e-coli sepsis
