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Flashcards in Metabolic Deck (11)
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What is the cause of mucopolysaccharidoses?

Abnormal accumulation of substrate in lysosomes.


  • A group of disorders in which acid mucopolysaccharides (glycosaminoglycans) are stored in the lysosomes due to various enzyme deficiencies.
  • If the diagnosis is suspected, an assay of the lysosomal enzymes should be performed (either on freshly isolated leucocytes or cultured fibroblasts)


How do mitochondrial disorders present?

Mitochondrial Disorders can present with any symptom in any organ at any age but are associated with a lactic acidosis.


How do organic acidemias/acidurias present?


  • maple syrup urine disease
  • methylmalonic acidemia
  • propionic acidemia
  • isovaleric acidemia

Organic Acidaemias are associated with acidosis and hyperammonemia (rather than the alkalosis and hyperammonemia of Urea Cycle Disorders).


Look for hypoglycemia, low pH, NH3 50-100.

Urinary ketones positive

Presents as neonate


How do neonatal peroxisomal disorders present?

(Adrenoleukodystrophy, Refsum, Acyl co A def, Zellwegers)

Affected individuals present at birth with a typical craniofacial dysmorphism.

  • High forehead
  • Large anterior fontanelle
  • Markedly separated cranial sutures
  • Hypoplastic supraorbital ridges
  • Upward slant of the eyes
  • Epicanthal folds
  • Low and broad nasal bridge
  • High arched palate
  • Deformed ear lobes


Hepatomegaly - associated with cirrhosis and biliary dysgenesis. Calcific stippling of the patellae, hips, and other epiphyses (chondrodysplasia punctata) is present in 50 to 70 percent. Other features are glomerulocystic kidney disease, cataracts, and pigmentary retinopathy. These abnormalities are already present at birth. 

Neurologic abnormalities include profound hypotonia and weakness with absent reflexes, severe impairment of hearing and vision, and neonatal seizures. Developmental delay is profound. Infants rarely survive beyond six months of age.


How do urea cycle disorders present?

egs of disorder....

  • ornithine transcarbalymase def.
  • N-Acetylglutamate synthase def.
  • citrullinemia
  • agininemia
  • argininosuccinic aciduria
  • carbamoyl phosphate synthetase I def.

Urea Cycle Disorders generally present with a progressive nonspecific acute encephalopathy with severe hypotonia. Breathing may be abnormally rapid producing respiratory alkalosis as a result of respiratory centre stimulation by high ammonia levels.


Key features

NH3 +++ (>200)

pH alkalotic 2º to NH3 stimulation

Usually present as neonate


How do Fatty Acid Oxidation disorders present?


  • HMG def
  • carnitine transport defect
  • and many many many more!

Hypoglycemia +++

normal or mildly elevated NH3

mild acidosis

Urinary ketones - negative

Presents in childhood with intercurrent illness.


How do patients with galactosemia typically present?

With an E. Coli sepsis


What does a deficiency in cobalamin or folate cause?

Megaloblastic anaemia


What does a deficiency in niacin cause?

The three D's

  1. Diarrhoea
  2. Dementia
  3. Dermatitis


What does a deficiency in Riboflavin cause?

Angular chelosis and glossitis


What does a deficiency in Thiamin cause?

Beri Beri