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Peroxisomal Disorders: Definition & Diagnosis

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson defines an uncommonly heard of group of disorders, called peroxisomal disorders. You'll learn what they are, some of their names, as well as some of the ways by which they can be diagnosed.

Peroxisomes

Imagine a little bag filled with tools that help you speed up your work. Maybe this bag has scissors, an electric drill, an electric air pump and what not. Our body's cells have similar tool bags and tools that help it speed up all sorts of important biochemical reactions. These tool bags are called peroxisomes and the tools they use to quicken the rate of biological reactions are called enzymes. In reality, peroxisomes are shaped like little inflated balloons in the cells and the enzymes are protein-based structures.

In any case, if there's something wrong with the tool bag or tools, you'd agree you'd have trouble getting your work done. That's no different in a peroxisomal disorder with respect to the proper function of the body.

In this lesson, we're going to cover the concept of peroxisomal disorders. We'll also go over the basics of how they are diagnosed.

Definition

A peroxisomal disorder is one of numerous genetically-based disorders that involve one of two problems:

1. Defective peroxisome formation. In other words, that tool bag of ours is defectively made.

2. A defect in an enzyme within the peroxisome. Meaning, the tool inside the tool bag is defective.

There are numerous such disorders, such as:

  • Zellweger syndrome. People with this syndrome are predisposed to seizures, liver problems, and improperly shaped faces among other things.
  • X-linked adrenoleukodystrophy. People with this type of peroxisomal disorder may have attention deficits, dementia, vision problems, and other issues.
  • Refsum's disease, which involves mental disabilities, growth retardation, and deafness.

Diagnosis

There is no single test that can diagnose all peroxisomal disorders. Thus, a multi-pronged approach may be taken in order to figure out what the problem might be. Importantly, a blood test could be taken to measure the increases of various compounds, such as VLCFAs. VLCFAs are very long chain fatty acids. They would normally be transformed and broken down if everything was ok with our tool bag and tools. But because they are defective, VLCFAs are elevated in the blood.

And this is important to remember for another set of tests, imaging studies. See, if VLCFAs aren't transformed and broken down to other substances, they might contribute to the demyelination of the central nervous system. The central nervous system is the brain and spinal cord. Demyelination refers to the stripping away of an important layer that surrounds nerve cells. This layer helps the nerve cells communicate with one another quickly and efficiently. It would be like stripping away the protective layer of a wire, basically. If demyelination occurs, a whole host of neurological abnormalities can result, some of which you learned about in the last section.

So, imaging studies may spot this demyelination in some peroxisomal disorders. To that end, a doctor may turn to MRI, or magnetic resonance imaging. MRI uses magnetic fields to help create a very detailed image of the soft tissue structures of the body, in this case the brain.

In some disorders, we can measure and note abnormal electrical activity in the brain as a result of the peroxisomal disorder. The test that measures and records this problem is called an EEG, or electroencephalogram.

The takeaway for you is that various lab tests and imaging tests are both used to diagnose and differentiate between the many peroxisomal disorders.

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