Expanding the Differential Diagnosis of Ultrasonographic Flexor Digitorum Profundus–Flexor Carpi Ulnaris Dissociation of Echogenicity: Muscular Dystrophies

Ultrasonographic FDP-FCU dissociation of echogenicity confirms selective deep finger flexor involvement. The differential diagnosis of this imaging sign includes IBM but also certain muscular dystrophies (BMD, DM1, DM2, and FSHD), which should be considered in uncommon presentations of suspected IBM or when additional supportive diagnostic findings thereof are lacking.