Contrasting echogenicity in flexor digitorum profundus–flexor carpi ulnaris: A diagnostic ultrasound pattern in sporadic inclusion body myositis



Introduction: In this study we aimed to clarify whether muscle ultrasound (US) of the forearm can be used to differentiate between patients with sporadic inclusion body myositis (s-IBM) and those with s-IBM–mimicking diseases. Methods: We compared the echo intensity (EI) of the flexor digitorum profundus (FDP) muscle and the flexor carpi ulnaris (FCU) muscles in patients with s-IBM (n = 6), polymyositis/dermatomyositis (PM/DM; n = 6), and amyotrophic lateral sclerosis (ALS; n = 6). Results: We identified EI abnormalities in 100% of patients with s-IBM, 33% of those with PM/DM, and 33% of those with ALS. An “FDP–FCU echogenicity contrast,” a US pattern involving a higher EI in the FDP than in the FCU, was observed in all patients with s-IBM, but in none of those with PM/DM or ALS. Conclusions: FDP–FCU echogenicity contrast in muscle US is a sensitive diagnostic indicator of s-IBM. Muscle Nerve 49: 745–748, 2014