“Boule du biceps” in dysferlinopathy

Eymard et al.¹ first described “boule du biceps” (bulging of biceps), a ball-like appearance caused by the selective atrophy of the distal half of the biceps brachii (BB) muscle, in patients with dysferliniopathy. This sign is also known as biceps lump. In our cohort of 24 patients with dysferlinopathy (22 symptomatic and 2 asymptomatic hyperCKemia), all confirmed both by the absence of dysferlin on muscle biopsy and by the presence of DYSF mutation on genetic analysis, except for 4 patients who were diagnosed only at the protein level. Among the 20 patients who were genetically confirmed, 18 were homozygotes for 3 different recurrent (c.342+1G>A, c.755C>T, and c.4431G>T) and 3 different nonrecurrent (c.1958delG, c.3944_3948delinsG, and c.5983_5984del) mutations, and 2 were compound heterozygotes of mutations different from those in other patients (c.2190dupA/c.3597G>A and c.4101G>A/c.6124C>T, respectively). Of note, we did not try to subclassify the clinical phenotype into Miyoshi myopathy and LGMD2B/LGMD-R2 dysferlin related as recent articles suggest that there is no essential difference in the pattern of muscle involvement, and thus, they are the same disease.^2–5 The BB was carefully observed during contraction and relaxation to check for the sign. The function of the upper limb (UL) was assessed using the Medical Research Council (MRC) scale. Furthermore, the BB was observed in patients with other muscular dystrophy in our cohort (DMD/BMD 118 cases, sarcoglycanopathy 12 cases, FSHD 5 cases, LGMD2A 18 cases, and other LGMDs 5 cases). Boule du biceps was observed in 71% (17/24) of our patients with dysferlinopathy, including the 2 asymptomatic ones. The UL MRC score was 4 or higher in the 17 patients who showed boule du biceps, but was 3+ or lower in the 7 patients who lacked the sign. None of the controls showed boule du biceps. MRI of the BB of the asymptomatic patient during arm flexion showed that the distal part of the short head was partially infiltrated by fat, whereas the long head and the proximal part of the short head were spared. MRI of the symptomatic patient showed moderate fat infiltration in the long head and in the distal part of the short head, whereas the proximal part of the short head was spared (figure). The sign was absent in patients with more marked muscle weakness, suggesting that even the proximal portion of the BB may be affected in the advanced stages and thus can no longer show contraction. Five of 7 patients who did not show boule du biceps were nonambulant, indicating that this sign disappears in advanced stage of the disease. Our findings suggest that the distal portion of the short head of the BB is affected even in early stages, whereas the proximal part is spared, which gives rise to boule du biceps. This can be a valuable diagnostic clinical feature for dysferlinopathy from early stages of the disease.