IMPORTANCE

Implementation of newborn screening (NBS) in the United States now detects infants with late-onset Pompe disease (LOPD), a lysosomal storage disease characterized by slowly progressive muscle weakness, and detailed clinical evaluation has identified early muscle weakness. Biomarkers may be uninformative; thus, non-invasive imaging is needed to assess early LOPD muscle changes. Muscle ultrasound (US) measuring echointensity (EI) is a non-invasive measure of muscle health.

OBJECTIVE

In this study, we aimed to evaluate if EI can identify characteristic patterns of muscle involvement in LOPD patients identified by NBS.

DESIGN/SETTING: Prospective, cross-sectional, single time point study.

SETTING

One-center study.

PARTICIPANTS

We examined 20 infants with NBS-identified LOPD (ages 5-20 months). All had standardized physical therapy assessments.

EXPOSURES

Creatine Kinase (CK) and Urine Hexose Tetrasaccharide (Glc4) were obtained. Muscle US of deltoid, biceps brachii, forearm flexors, thoracic paraspinals, gluteus maximus, quadriceps, tibialis anterior and medial gastrocnemius was performed.

MAIN OUTCOMES AND MEASURES

Mean EI was calculated for all involved muscle groups. Quantitative EI Sum Scores were calculated as total EI divided by number of muscle groups assessed. We performed a comprehensive literature review to compare our results to previous LOPD muscle ultrasound studies.

RESULTS

Six of 20 participants had elevated CK and 15 had 50% of the most common concerning kinematic physical findings; with normal urine Glc4 in all except one. Based upon muscle EI, the most affected muscles were quadriceps and medial gastrocnemius, with notable elevated EI in thoracic paraspinals. Biceps brachii was the most frequently affected upper extremity muscle. EI sum scores correlated moderately with increasing CK. Statistically significant positive correlation was found between posterior pelvic tilt in sitting and EI of gluteus maximus. Sonographic pattern of muscle involvement was similar to previous studies assessing older patients with LOPD.

CONCLUSIONS AND RELEVANCE

In this study, muscle EI was elevated most often in the quadriceps, tibialis anterior, medial gastrocnemius, thoracic paraspinals, and biceps brachii. Involved muscles generally fit the profile of physical and muscle ultrasound/MRI exam findings in LOPD patients. Muscle ultrasound is recommended for rapid, focused muscle assessment in LOPD, especially those identified via NBS. Future studies should focus on this pattern of ultrasonographic abnormality and changes over time.