Department of Pathology, University of Oklahoma Health Sciences Center

NeuroTest Question #63 Next question Previous question

Answer: Carnitine deficiency (D)  Level of difficulty: 4 NeuroTest NeuroLearn NeuroHelp

Discussion: 

• Pathology of the case: What is being illustrated is a muscle biopsy under medium magnification electron microscopy. The myofibrils on the left of the picture provide the hint for identification of tissue. There is substantial accumulation of round, amorphous, homogeneous acellular substance that are not membrane bounded. These features indicate that these are neutral fat (lipid) droplets. The storage can be well demonstrated also by oil red O stain. [Click here to see a photo of Oil red O stain in abnormal neutral fat (lipid) storage]
• Pompe's disease is the infantile variant of glycogenosis (glycogen storage disease) type II due to deficiency of a-1,4-glucosidase. In contrast to other glycogenosis, this type is a lysosomal storage disease and the storage material is membrane bound. [Click here to learn more on Pompe's disease]
• McArdle's disease or glycogenosis (glycogen storage disease) type V is due to deficiency of the muscle isoform of phosphorylase. In contrast to Pompe's disease, the glycogen is not membrane bound. [Click here to see a case of McArdle's disease]
• Zellweger syndrome (Cerebrohepatorenal syndrome of Zellweger)  is a peroxisomal disease that is  biochemically characterized by abnormal accumulation of very long chain fatty acid, and morphologically characterized by a neuronal migration defect, typically pachymicrogyria, affecting both the cerebral hemisphere and cerebellar hemisphere. This is the first syndrome known in which malformations of the brain and other organs are associated with an inborn error of metabolism. The peroxisomal Beta-oxidation is impaired and lead to the accumulation of saturated very long chain (over 22 carbon) fatty acid (VLCFA). Measurment of VLCFA level is the mainstay of biochemical diagnosis. It is transmitted in an autosomal recessive trait. Its main microscopic feature is abnormal assembly of persoximes. At ultrastructural level, various inclusion bodies have been described. Macrophages containing lipid droplets and lamellae are present. [Click here to learn more about Zellweger syndrome]
• Carnitine deficiency: This is a metabolic disorder of fat metabolism and will lead to intracytoplasmic neutral fat (lipid) accumulation.

Comment: KarMing-Fung@ouhsc.edu