Duchenne muscular dystrophy coexisting with Down syndrome or Turner syndrome: Two case reports

Figure 1 Histopathological and immunohistochemical findings from quadriceps muscle biopsies confirming dystrophinopathy. A-D: A 6-year-old boy with Duchenne muscular dystrophy (DMD) and Down syndrome (Case 1); E-H: A 6-year-old girl with DMD and mosaic Turner syndrome (Case 2). A: Hematoxylin and eosin (H&E) staining demonstrating myopathic changes, including mild-to-moderate fiber size variation, scattered necrotic and regenerating fibers with clustered regeneration, and mild-to-moderate endomysial fibrosis with adipose tissue infiltration; B: Diffuse utrophin positivity, indicating compensatory upregulation secondary to dystrophin deficiency; C: Absent dystrophin C-terminal (Dys-2) staining in most fibers; D: Faint dystrophin rod domain (Dys-1) staining; E: H&E staining demonstrating dystrophic changes similar to Case 1; F: Biphasic utrophin staining pattern consistent with mosaic dystrophin expression; G: Biphasic Dys-2 staining: Fibers with weak utrophin staining demonstrate dystrophin positivity, whereas fibers with strong utrophin staining are dystrophin-negative; H: Biphasic Dys-1 staining showing a reciprocal pattern to utrophin expression, reflecting mosaic X-chromosome inactivation. Original magnification × 200; scale bar = 20 μm.