Duchenne Muscular Dystrophy (DMD)

6 y/o M with h/o delayed crawling/walking as compared to siblings presents with fatigue, falls. Pt had difficulty holding his head up as an infant. Parents first became concerned lower extremity muscle weakness when pt was 2-3 y/o. Calf pseudohypertrophy, lower extremity muscle weakness, scoliosis on exam.

• Labs

  • Obtain serum thyroxine, TSH, vitamin D

  • Serum creatinine kinase between 3,000 and 50,000 U/L

  • Obtain genetic analysis to confirm diagnosis

• Treatment

  • Vitamin D < 30 ng/mL; start vitamin D supplementation

  • Start prednisone 0.75 mg/kg/day to slow disease progression, improve outcomes

  • Regular, gentle exercise recommended to prevent disuse atrophy

  • Refer to pediatric neurology, pediatric cardiology

  • Decreased growth velocity: Refer to pediatric endocrinology

• Parents advised that fatal complications are generally due to late pulmonary and cardiac involvement

Notes

• Most common fatal disease affecting children

• Head lag due to neck muscle weakness is a specific, early presentation

• On average, two years elapse between initial parental concern and formal diagnosis

• Rule out hypothyroidism as it can mimic DMD

• If serum CK elevated but less than 3,000 U/L, repeat testing in 2-3 weeks

• Patients are at increased risk of long-bone fracture due to decreased mobility, corticosteroid use