HISTORY
Otherwise healthy 9-year-old African American boy seen for first time for complaints of frequent exhaustion, particularly when climbing stairs or walking for long periods. He could no longer participate in sports because of inability to keep up with his peers. He had been toe walking and had become clumsier over the past year, tripping and falling more frequently. Besides a mild delay in walking (around 16 months), his mother had reported no outstanding gross motor delays in infancy. He was in a regular class in school, although he did receive extra help in math and reading.
PHYSICAL EXAMINATION
He had hypertrophic calf muscles and significant thigh muscle wasting. Gait was abnormal and unsteady, with mild weakness noted bilaterally in the lower extremities. Deep tendon reflexes were normal, and cranial nerves II through XII were intact. The remainder of the physical findings were unremarkable.
LABORATORY FINDINGS
Blood tests revealed an extremely elevated creatine phosphokinase (CPK) level (17,863 IU/L [normal, less than 160 IU/L]) and elevated liver transaminase levels (aspartate aminotransferase [AST], 382 U/L; and alanine aminotransferase [ALT], 682 U/L).
"WHAT'S YOUR DIAGNOSIS?"
REFERENCES:
1. Deconinck N, Dan B. Pathophysiology of Duchenne muscular dystrophy: current hypotheses. Pediatr Neurol. 2007;36:1-7.
2. Bigger WD, Klamut HJ, Demacio PC, et al. Duchenne muscular dystrophy: current knowledge, treatment, and future prospects. Clin Orthop Relat Res. 2002;401:88-106.
3. Finder JD, Birnkrant D, Carl J, et al; American Thoracic Society. Respiratory care of the patient with Duchenne muscular dystrophy: ATS consensus statement. Am J Respir Crit Care Med. 2004;170:456-465.
4. Takeshima Y, Yagi M, Okizuka Y, et al. Mutation spectrum of the dystrophin gene in 442 Duchenne/Becker muscular dystrophy cases from one Japanese referral center. J Hum Genet. 2010;55:379-388.
5. Cohn RD, Campbell KP. Molecular basis of muscular dystrophies. Muscle Nerve. 2000;23:1456-1471.
6. Zamora S, Adams C, Butzner JD, et al. Elevated aminotransferase activity as an indication of muscular dystrophy: case reports and review of the literature. Can J Gastroenterol. 1996;10:389-393.
7. Balaban B, Matthews DJ, Clayton GH, Carry T. Corticosteroid treatment and functional improvement in Duchenne muscular dystrophy: long-term effect. Am J Phys Med Rehabil. 2005;84:843-850.
8. Ogata H, Ishikawa Y, Ishikawa Y, Minami R. Beneficial effects of beta-blockers and angiotensin-converting enzyme inhibitors in Duchenne muscular dystrophy. J Cardiol. 2009;53:72-78.
9. Yokota T, Lu QL, Partridge T, et al. Efficacy of systemic morpholino exonskipping in Duchenne dystrophy dogs. Ann Neurol. 2009;65:667-676.
10. Odom GL, Gregorevic P, Chamberlain JS. Viral-mediated gene therapy for the muscular dystrophies: successes, limitations and recent advances. Biochim Biophys Acta. 2007;1772:243-262.
11. Wagner KR, Fleckenstein JL, Amato AA, et al. A phase I/II trial of MYO-029 in adult subjects with muscular dystrophy. Ann Neurol. 2008;63:561-571.