Quantitative muscle ultrasound as a window into disease progression in infantile-onset Pompe disease

Background

Infantile-onset Pompe disease (IOPD) is caused by a deficiency of the enzyme acid alfa glucosidase, resulting in glycogen accumulation in muscles and other tissues. Without treatment, affected infants typically die within two years. Enzyme replacement therapy (ERT) has significantly improved survival and functional outcomes, especially with early initiation, higher dosing, immune modulation, and newer therapeutic options. However, effective noninvasive tools to monitor disease progression and treatment response are still needed. Quantitative muscle ultrasound (QMUS) may serve as a useful alternative.

Objective

To evaluate the effectiveness and feasibility of QMUS for monitoring muscle involvement in IOPD.

Methods

This study assessed echo intensity (EI) measurements from QMUS in eight patients with IOPD receiving long-term ERT. EI was recorded annually in seven muscle groups. EI >50 units was considered abnormal, and a composite EI Sum Score was calculated. These values were compared with Gross Motor Function Measure (GMFM) scores using univariable regression.

Results

Patients began ERT at a median age of 7 weeks. QMUS assessments were performed, with ages ranging from 7 months to 21 years (median age of 9.5 years) at first evaluation. All patients had at least one muscle group with abnormal EI. Upper extremity EI was significantly lower (mean 47.3) than lower extremity muscle groups (mean 64.1, p = 0.002). Higher EI scores correlated with more severe myopathy and wheelchair use, while lower scores reflected better motor outcomes.

Conclusions

QMUS is a promising noninvasive tool for monitoring muscle health in patients with IOPD receiving ERT. It may aid in assessing disease progression and treatment efficacy.