Fastex Improves Range of Fabry Disease Diagnostic Tools

Fabry disease is an inherited disorder caused by a mutation found on the X chromosome. Inadequate functioning of the lysosomal enzyme α‑Galactosidase‑A causes a rare lysosomal storage disorder.  Doctors usually diagnose the prevalence and severity of this disease with the Mainz Severity Score Index (MSSI) as well as the Fabry disease severity scoring system (DS3).   

Although MSSI and DS3 can assess the severity of Fabry disease, researchers discovered that both are less effective at detecting a change in the disease's state than Fastex which fills in this measurement gap. 

Misdiagnosis Common for Fabry Disease

Because Fabry disease is rare and other diseases have similar symptoms to it, misdiagnosis is common and can lead to life-threatening complications, such as a heart attack, stroke, or kidney damage. For this reason, finding the best diagnostic tools can make a significant difference in successfully diagnosing Fabry disease.

Fabry disease affects about 1 in 40,000 to 60,000 men in the United States. Although it also occurs in women, researchers have not been able to statistically evaluate the extent of its prevalence. Most patients experience a mild version of the disease and only experience it later in life when it affects vital organs like the heart or kidneys. 

This X-linked lysosomal disorder precipitates heavy deposits of neutral glycosphingolipids such as globotriaosylceramide (Gb3) to disrupt the healthy function of essential organs like the brain, heart, kidney, eyes, and skin. Over time, as endothelium, epithelial, and smooth muscles accumulate glycosphingolipid deposits in the vascular muscle cells of the peripheral nervous system, patients experience a wide range of signs and symptoms

Patients may have stomach pain and bowel movements after a meal.  They may experience ringing in their ears, deafness, and cloudy vision.

Although they rarely sweat after exercising, they may experience  pain and burning sensations in their hands and feet. Many also get a fever after exercising. Hot weather also affects them in a similar way.

Study Measures Efficacy of MSSI, DS3, and Fastex

A new study of 62 people with Fabry Disease measured the efficacy of MSSI, DS3, and Fastex in determining treatment outcomes. 

The researchers concluded that while MSSI and DS3 helped in the initial diagnosis of Fabry disease, particularly in measuring its severity, Fastex served as a more effective tool for assessing patient stability or disease progression over a period of time.

Researchers separated patient evaluations with the different tools by the span of a year. During this time all participants in the study received enzyme replacement therapy (ERT). In the United States, the FDA has approved the use of a product called Fabrazyme® by Sanofi-Genzyme.

An alternative ERT therapy treatment is the use of Galaford® by Amicus Therapeutics. Both administer α‑Galactosidase‑A but in different ways. Fabrazyme® delivers the enzyme intravenously while Galaford® delivers it orally.

The Benefits of MSSI and DS3

As a clinical scoring system, the Mainz Severity Score Index (MSSI) allows clinicians to measure the severity of a patient’s signs and symptoms. The tool also allows clinicians to keep track of the progress a patient makes with their ERT treatment. 

As a clinical scoring system, the Fabry disease severity scoring system (DS3) plays a similar role as MSSI to quantify the severity of the disease burden, monitor the progression of the disease, and evaluate the response to ERT treatments. 

The difference between the two scoring systems is how they measure the signs and symptoms of the disease. 

The Benefits of Fastex

As a clinical scoring system, the FAbry STabilization indEX (FASTEX) is slightly different than MSSI and DS3. This is more of an innovative index that allows clinicians to assess the clinical stability of Fabry disease patients over time.

Comparison and Contrast of Fastex over MSSI and DS3

Fastex is more effective than MSSI and DS3 for measuring patient stability over time because it not only measures the effects of the disease on the nervous system, kidneys, and heart, but it is also easier to use. While MSSI uses 24 items and DS3 uses 12 items, Fastex only uses 7 items.

Because it doesn’t obscure the data with factors that don’t change over time, Fastex is more sensitive to changes in the disease, which often means disease progression. For instance, Fastex doesn’t measure angiokeratoma or cornea verticillata because neither of these conditions changes much over time.

Angiokeratoma is a cutaneous abrasion of capillaries that is visible as it changes from red to blue color. It is benign and marked by hyperkeratosis, a congealing of the stratum corneum. Cornea verticillata are corneal deposits of the basal epithelium that create a golden-brown whorl pattern. 

In conclusion, it is important to clarify that this study was not about which tool works better but instead measured how the tools affected treatment outcomes.  Doctors should use them all because they all work, although in slightly different ways. The study essentially provided a clearer idea of the benefits of each tool.

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