The heart weight to tibia length ratio was similar in dystrophin-deficient mdx mice (5.5 ± 0.2 vs. 5.9 ± 0.2 mg/mm, respectively) at 22 weeks old and age-matched control C57BL10 mice, indicating no cardiac hypertrophy in mdx mice at this age. The gene discussed is DMD; the disease is cardiac hypertrophy.