B-Oxidation

Question 1

Medium-chain Acyl Dehydrogenase Deficiency

Answer 1

Cause: deficiency in MCAD (most common Autosomal Recessive disorder of lipids)
Result: No B-Oxidation of medium chain FA
Sx: Severe reduction in energy production, hypoketonemia & hypoglycemia (esp, in infants/children), MCFA metabolites in urine, hepatomegaly with lipid deposits and altered mito structure.
Keywords: linked to Sudden Infant Death Syndrome (SIDS) (10% of cases)

Question 2

Jamaican Vomiting Sickness

Answer 2

Cause: Ingestion of unripe Akee fruit (has rare AA=Hypoglycin, which is metabolized to Methylenecyclopropylacetyl-CoA [MCPA-CoA], an irreversible inhibitor of short and MCFA Acyl-CoA Dehydrogenase
Result: Unable to carry out B-Oxidation of short and MCFA
Sx: Hypoglycemia, hypoketonemia > vomiting, convulsions, and metabolic coma

Question 3

Refsum’s Disease (phytanc Acid Storage Syndrome)

Answer 3

Cause: Inability to metabolize Phytanic Acid becasue of deficiency in Phytanic Acid Alpha-hydroxylase Enzyme
Result: Acuumulation of Phytanic acid in tissues and blood
Sx: Characterized by progressive neurological defects (tremors, unsteady gait, & def night vision), Metabolic Acidosis due to accumulation of an acid, peripheral nerves demyelination & hypoertrophy due to Schwann cell proliferation
Tx: significant improvement with strict diet free of phytanic acid, which is most plants plus some meat and diary.
Keywords: Autosomal recessive

Question 4

Zwellweger’s Syndrome

Answer 4

Cause: Peroxisomal disorder (defective peroxins made > defective peroxisomal biosynthesis)
Result: Relative absence of peroxisomes in cytosol and thus accumulation of VLCFA’s in plasma and tisues
Sx: CNS swelling
Tx:
Dx:
Keywords:

Question 5

Ketosis

Answer 5

Cause: Generation of ketone bodies > usage Due to: 1) Type I diabetes (lack insulin which regulates KB synthesis in the fasted state). 2) starvation: prolonged fasting > B-Ox run for 36-48 hours > OAA depleted due to gluconeogenesis > more acetyl CoA shunted to KB synthesis
Result: XS KB in blood and urine
Sx: ketoacidosis, XS H+ in urine with K+ Na+ & H2O > DEHYDRATION, KB in blood an urine, acetone breathe (acetoacetate > ketone coversion)