Magnetic resonance spectroscopy (MRS) — a specialized imaging test to visualize and measure the amount of fat in certain regions of the body — may help monitor disease severity and treatment response in people with Gaucher disease, a pilot study suggests.
The study, “Gaucher disease status and treatment assessment: pilot study using magnetic resonance spectroscopy bone marrow fat fractions in pediatric patients,” was published in the journal Clinical Imaging.
Gaucher disease is caused by a mutation in the GBA gene, which compromises the production of beta-glucocerebrosidase, an enzyme responsible for breaking down a fatty substance called glucocerebroside. As a result, glucocerebroside gradually builds up inside immune cells called macrophages, which then become Gaucher cells that infiltrate the liver, spleen, bone marrow, and nervous system.
Measuring the amount of fatty tissue within the bone marrow through specialized magnetic resonance imaging (MRI) is one way physicians can assess disease severity in people with Gaucher.
Despite the success of these MRI-based techniques, most institutions do not use them on a routine basis due to the high level of technical expertise they require. MRS has been proposed as an alternative approach to evaluate fat content in the bone marrow due its wider availability and high accuracy.
A previous study based on MRS reported significant differences in fat fraction of the bone marrow between patients with type 1 Gaucher and healthy individuals.
In the new study, investigators in the U.S. explored in more detail the effectiveness of MRS at distinguishing those with Gaucher from healthy individuals based on the amount of fatty tissue within their bone marrow.
The study was based on data from six children and young adults with Gaucher (average age 12.9), and six healthy individuals (controls) of approximately the same age.
Investigators compared bone marrow fat fractions and bone marrow burden (BMB) scores in the femoral neck (the upper portion of the femur bone in the thigh) and lumbar spine (vertebrae of the lower back) of all study participants. The BMB score is a measure of Gaucher cell infiltration into the bone marrow, with higher scores reflecting higher infiltration.
A separate analysis of six children currently on enzyme replacement therapy (ERT) was also performed to assess the usefulness of MRS at evaluating treatment response in people with Gaucher. These patients were followed over an average period of 3.5 years.
Findings revealed that untreated patients had significantly lower bone marrow fat fractions in both the femoral neck (0.32 vs. 0.67 in controls) and lumbar spine (0.17 versus 0.34 in controls). In contrast, BMB scores were significantly higher in patients (8.0) compared to controls (3.5).
For those on ERT, the bone marrow fat fraction in the femoral neck was the only parameter associated with treatment duration, when adjusted for age.
This parameter was also correlated with fat fraction in the lumbar spine, liver volume, and chitotriosidase levels (a biomarker of macrophage activation that is usually high in patients with Gaucher).
Further analyses confirmed the reliability of repeated MRS measurements and BMB rater scores.
“The findings of this small, pilot study of pediatric and young adult patients offer support for the use of MRS as an alternative method … to measure fat fractions in Gaucher disease,” the investigators wrote.
“These findings suggest MRS-derived bone marrow fat fractions could be useful in assessing disease severity and treatment response in children and young adults with Gaucher disease, pending further investigation in a larger, multicenter prospective study,” they added.
