A 4-year-old boy is brought to the physician for a follow-up examination. He has a 1-year history of progressive hypotonia. Serum lactate is increased. He has a 6-year-old brother with poor hearing and vision. A muscle biopsy from the patient is shown. Which of the following is most likely to be seen in this patient?
Constitutive activation of FGFR3
Decreased functionality of α-/β-dystroglycan
Deficiency of α1,4-glucosidase
Frameshift mutation in X-chromosomal gene
Heteroplasmic neurosensory deficits
