Qualitative and quantitative skeletal muscle ultrasound in late‐onset acid maltase deficiency

INTRODUCTION: Acid maltase deficiency (AMD, or Pompe disease) is an inherited myopathic disorder of glycogen degradation. Diagnosis is often delayed. Muscle ultrasound could improve diagnosis. METHODS: We compared skeletal muscle ultrasound images from adults with AMD (n = 10) to other myopathies (n = 81) and, in AMD, compared qualitative (Heckmatt) and quantitative (backscatter) ultrasound measurements with strength and function. RESULTS: Qualitative ultrasound was abnormal in at least one muscle in all AMD subjects. Ultrasound patterns specific for AMD were: normal triceps brachii despite abnormalities in elbow flexors (89% vs. 17%, P < 0.0001); focal abnormalities affecting deep more than superficial biceps brachii (40% vs. 4%, P = 0.002); and more severe involvement of vastus intermedius than rectus femoris (40 vs. 11%, P = 0.03). In AMD, both qualitative (Heckmatt) and quantitative (backscatter) ultrasound measures increased with decreasing strength and function. CONCLUSIONS: Muscle ultrasound identifies the presence and specific patterns of AMD pathology, measures disease severity, and can help in the diagnosis of AMD.