Diamond on quadriceps: a frequent sign in dysferlinopathy.

Patients with dysferlinopathy (11 limb girdle muscular dystrophy [LGMD]-2B and 16 Miyoshi myopathy) were asked to stand with knees slightly bent so that the quadriceps muscles were in moderate action. The anterolateral aspect of thighs was observed for any abnormal bulge. Nineteen patients (7 LGMD-2B and 12 Miyoshi myopathy) showed asymmetric diamond shaped bulges with wasting of muscles above and below (figure). The sign was not apparent in standing or sitting position. Diamond on quadriceps sign indicates selectivity of dystrophic process not only among different muscles but also within a muscle as suggested earlier.1 The sign was absent in other muscular dystrophies, suggesting specificity for dysferlinopathy. It would add to the calf-head sign described earlier in Miyoshi myopathy.2