Disorders of fatty acid metabolism: Pathology review

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Disorders of fatty acid metabolism: Pathology review


Biochemistry and metabolism


Citric acid cycle

Electron transport chain and oxidative phosphorylation


Glycogen metabolism

Pentose phosphate pathway

Physiological changes during exercise

Amino acid metabolism

Nitrogen and urea cycle

Fatty acid synthesis

Fatty acid oxidation

Ketone body metabolism

Cholesterol metabolism

Metabolic disorders

Essential fructosuria

Hereditary fructose intolerance


Pyruvate dehydrogenase deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency

Lactose intolerance

Glycogen storage disease type I

Glycogen storage disease type II (NORD)

Glycogen storage disease type III

Glycogen storage disease type IV

Glycogen storage disease type V


Metachromatic leukodystrophy (NORD)

Krabbe disease

Gaucher disease (NORD)

Niemann-Pick disease types A and B (NORD)

Niemann-Pick disease type C

Fabry disease (NORD)

Tay-Sachs disease (NORD)

Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)

Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)


Hartnup disease


Ornithine transcarbamylase deficiency

Phenylketonuria (NORD)

Cystinuria (NORD)


Maple syrup urine disease


Familial hypercholesterolemia



Disorders of carbohydrate metabolism: Pathology review

Disorders of fatty acid metabolism: Pathology review

Dyslipidemias: Pathology review

Glycogen storage disorders: Pathology review

Lysosomal storage disorders: Pathology review

Disorders of amino acid metabolism: Pathology review


Disorders of fatty acid metabolism: Pathology review

USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

of complete

A 6-day-old infant is brought to a local emergency department after being found unresponsive by the patient’s parents. The neonate is promptly admitted to the NICU and is given D10 normal saline and a bicarbonate infusion. Overnight, the patient develops generalized seizure activity. An MRI performed the following day reveals hypoxic-ischemic encephalopathy. Initial laboratory findings and newborn screening results are demonstrated below. Which of the following is the most likely diagnosis?  


Content Reviewers

Antonia Syrnioti, MD


Jung Hee Lee, MScBMC

Antonella Melani, MD

Evan Debevec-McKenney

Two kids are brought to the clinic by their mothers. The first one’s Dalia, a 2 year old girl. Her mother is concerned because Dalia always seems to be tired and weak, and in general doesn’t eat much. On physical examination of the abdomen, you palpate an enlarged liver. You decide to run a blood test, which reveals that her blood glucose and ketone bodies are decreased, but what really stands out to you is that her carnitine levels are also really low.

After Dalia, you see Luca, a 3 year old boy who had a brief seizure earlier that day. Luca’s mother tells you that he’s had gastroenteritis for the past few days, so he’s been vomiting and not eating much. You decide to run a blood test, which also reveals low blood glucose and ketone bodies, but unlike Dalia, he has high levels of fatty acyl-carnitine.

Based on the initial presentation, both Dalia and Luca seem to have some fatty acid metabolism disorder. Now, let’s review fatty acid metabolism real quick. Normally, the body's main source of energy is the glucose we get from food. When glucose is running low, like with prolonged fasting or exercise, the body is able to obtain energy from stored fats.

The simplest form of fats are fatty acids, which are grouped by length into short, medium, long, and very long chain fatty acids. Short and medium chain fatty acids are primarily obtained from the diet, while long and very long chain fatty acids can be synthesized from acetyl-CoA by the liver and fat cells.

Now, keep in mind that acetyl-CoA is usually found in the mitochondrial matrix, whereas the enzymes required for fatty acid synthesis are all in the cytoplasm. For acetyl-CoA to cross the mitochondrial membranes and get to the cytoplasm, it first needs to combine with oxaloacetate to form citrate. Once in the cytoplasm, an enzyme called citrate lyase leaves citrate back into acetyl-CoA and oxaloacetate. This whole process is called the citrate shuttle.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Fetal Fatty Acid Oxidation Disorders, Their Effect on Maternal Health and Neonatal Outcome: Impact of Expanded Newborn Screening on Their Diagnosis and Management" Pediatric Research (2005)
  6. "A Fetal Fatty-Acid Oxidation Disorder as a Cause of Liver Disease in Pregnant Women" New England Journal of Medicine (1999)

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