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MRCPCH > Metabolic medicine > Flashcards

Metabolic medicine Flashcards

1
Q

Features of propionic acidaemia

A
  • Defective propionyl-coenzyme A carboxylase
  • Causes accumulation of propionic acid
  • Early symptoms: Vomiting, dehydration, hypothonia, lethargy, and seizures
  • Later symptoms: Encephalopathy, movement disorders (basal ganglia damage), and low IQ
  • Treatment is with a low-protein diet, L-carnitine and biotin supplementation
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2
Q

Features of isolvaleric acidaemia

A
  • Mutation or deficiency in isovaleric acid-CoA dehydrogenase
  • Causes build up of isovaleric acid (smells of sweaty feet)
  • Symptoms: Lethargy, poor feeding, vomiting, seizures, and encephalopathy
  • Treatment is with a protein-restricted diet and L-carnitine
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3
Q

Features of methylmalonic acidaemia

A
  • Defect in the conversion of methylmalonyl-CoA to succinyl-CoA
  • Causes accumulation of methylmalonic acid
  • Symptoms: Lethargy, vomiting, dehydration, seizures, recurrent infections, progressive encephalopathy, stroke
  • Ketoacidosis and hyperammonemia can be seen during infective episodes
  • Treatment is with a protein-restricted diet, L-carnitine and cobalamin supplementation
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4
Q

Features of maple syrup urine disease

A
  • Decreased levels of alpha-keto acid dehydrogenase enzyme
  • Causes an accumulation of branched chain amino acids (BCAAs), allo-isoleucine, and branched-chain ketoacids
  • Symptoms: Hypotonia, poor feeding, vomiting, lethargy, seizures, and encephalopathy
  • Treatment is with leucine and branched-chain amino acid (BCAA)-free nutrition and supplementation with isoleucine and valine
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5
Q

What does the smooth endoplasmic reticulum do?

A

Synthesis of steroids and lipids

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6
Q

What does the peroxisome do?

A

Catabolism of very long chain fatty acids and amino acids
Results in the formation of hydrogen peroxide

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7
Q

How common is PKU/MCADD in the UK?

A

Both 1:10,000

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8
Q

How common are MSUD, IVA, GA1, or HCU in the UK?

A

All 1:100,000

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9
Q

Which metabolic diseases are screened for in the UK?

A
  • Phenylketonuria (PKU)
  • Medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
  • Maple syrup urine disease (MSUD)
  • Isovaleric acidaemia (IVA)
  • Glutaric aciduria type 1 (GA1)
  • Homocystinuria (pyridoxine unresponsive) (HCU)
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10
Q

Features of alkaptonuria

A
  • Autosomal recessive condition characterised by homogentisic acid oxidase deficiency. This leads to an accumulation of homogentisic acid.
  • Homogentisic acid is rapidly cleared by the kidney. If the urine is left standing, however, it oxidises to form a pigmented polymer which colours the urine black.
  • Over time, a similar process occurs with homogentisic acid in the body and it is deposited in cartilage, causing blue/grey discolouration in young adulthood (a process called ochronosis). These changes can be seen in cartilage, tendons, nail beds, eyelids, axillae, genital areas and buccal mucosa.
  • Deposition in the heart can cause cardiac valve problems, particularly aortic stenosis. Nearly all patients develop arthritis and joint pains due to deposition in joints.
  • Treatment includes protein restriction and vitamin C supplementation.
  • The main differential diagnosis is acute intermittent porphyria.
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11
Q

Features of PKU

A

musty body odour, eczema, hyperactivity, developmental delay, behaviour problems, convulsions, and low IQ.

Normal at birth

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12
Q

Radiological findings in vitamin D deficiency

A
  • Poor mineralisation
  • Delayed development of epiphyses
  • Irregularly widened epiphyseal plates
  • Increased distance between the end of shaft and the epiphyseal center
  • Cortical spurs projecting at right angles to the metaphysis
  • Coarse trabeculation (as opposed to the ground-glass pattern seen in scurvy)
  • Periosteal reaction
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13
Q

Common features of peroxisomal disorders

A
  • Developmental delay
  • Psychomotor retardation
  • Skeletal and craniofacial dysmorphism
  • Neonatal seizures
  • Liver dysfunction
  • Progressive sensorineural hearing loss
  • Retinopathy and cataracts
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14
Q

Diagnostic features of peroxisomal disorders

A
  • Elevated blood levels of very long chain fatty acids (VLCFA)
  • Elevated phytanic acid and pipecolic acid
  • Elevated bile acid intermediates
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15
Q

What kind of disorder are the following:

  • Zellweger syndrome
  • Infantile and classic Refsum’s disease
  • Rhizomelic chondrodysplasia punctata
  • X-linked adrenoleukodystrophy
A

Peroxisomal disorders

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16
Q

Causes of normal anion gap acidosis

A

H - Hyperalimentation/hyperventilation
A - Acetazolamide
R - Renal tubular acidosis
D - Diarrhoea
U - Ureteral diversion
P - Pancreatic fistula/parenteral saline

17
Q

Features of Hartnup disease

A
  • Reduced absorption and transport of amino acids leading to B3 deficiency
  • Clinical features:
    • Most children are asymptomatic
    • Pellegra like rash (photosensitive)
    • Diarrhoea
    • Failure to thrive
    • Ataxia
    • Aminoaciduria
    • Low IQ, poor growth, neurologic features, ocular features, and psychiatric features are less common
    • Urine chromatography aids diagnosis (increased amino acids in urine) coupled with normal plasma amino acids
    • Jejunal biopsy or skin biopsy may be needed
  • Exacerbators:
    • Sunlight (most common)
    • Pyrexia
    • Poor nutrition
    • Exercise
    • Physical or emotional stress
    • Medications
18
Q

Causes of low anion gap acidosis

A

Haemorrhage
Nephrotic syndrome
Intestinal obstruction

19
Q

Hormones increased in stress response

A
  • GH
  • Cortisol
  • Renin
  • Adrenocorticotrophic hromone
  • Aldosterone
  • Prolactin
  • ADH
  • Glucagon
20
Q

Hormones decreased in stress response

A

Insulin, testosterone, oestrogen

21
Q

Features of hereditary fructose intolerance

A
  • Deficiency of the enzyme (aldolase B) needed to metabolise fructose
  • Autosomal recessive metabolic condition
  • Even small amounts of fructose cause low blood sugar levels
  • Symptoms include vomiting, poor eating, failure to thrive, hypoglycemia, haemorrhage, jaundice, hepatomegaly, hyperuricemia
  • If sugars are not excluded, it can lead to liver and renal failure
  • Treatment is with life-long exclusion of fructose, sucrose, and sorbitol
  • Sugars which patients are able to metablise include glucose and maltose
  • Attacks of hypoglycaemia are treated with glucose (oral or IV)
22
Q

Features of nonketotic hyperglycinaemia

A
  • Also called glycine encephalopathy
  • Autosomal recessive
  • Type of inborn error or metabolism
  • 80% due to mutations in the GLDC gene, and 10-15 % due to mutations in the AMT gene
  • Defects in the glycine cleavage system causing high levels of glycine in CSF and the brain where it does most of its damage
  • Glycine is both an amino acid and a neurotrasmitter
  • Neurological symptoms and signs are most common
  • Majority presents in neonates, but can present in first 6 months
  • Presents with lethargy, feeding difficulties, myoclonic jerks, hypotonia, seizures, apnoea, and sometimes death
  • In surviving infants, difficulty epilepsy, developmental delay, and intellectual disability is common
  • Milder forms exist which present later
  • Currently no treatment exists, but trials suggest treatment with sodium benzoate and N-methyl D-aspartate (NMDA) receptor site antagonists may be effective
  • Other treatments include: antiepileptic drugs, ketogenic diet, gastrostomy tube, treatment for gastroesophageal reflux, and physical therapy
  • Sodium valproate is contraindicated as it increases glycine levels
  • Overall prognosis is better in males
23
Q

Causes of ketotic hypoglycaemia

A

Glycogen storage disease
Adrenal insufficiency
Organic acidurias
Maple syrup urine disease

24
Q

Causes of non ketotic hypogylcaemia

A

Hyperinsulinism
Disorders of fructose or galactose metabolism
Fatty acid oxidation
Growth hormone deficiency

25
Q
A

MRCPCH (8 decks)

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