Abstract Details

Title Exercise-Induced Rhabdomyolysis: Atypical Phenotype of a Dystrophinopathy

Topic Child Neurology and Developmental Neurology

Presentation(s) P1 - Poster Session 1 (9:00 AM-5:00 PM)

Poster/Presentation
Number 133

Objective Dystrophinopathies need to be included in the diagnostic evaluation of metabolic-like myopathies.

Background Duchenne muscular dystrophy (DMD) is a progressive X-linked recessive neuromuscular disorder caused by dystrophin gene mutations resulting in insufficient-to-absent functional dystrophin, a cytoskeletal protein that enables the strength, stability, and functionality of myofibers1. Dystrophin gene is predominantly expressed in skeletal and cardiac muscle with small amounts expressed in the brain. Typical DMD begins early in childhood with progressive proximal weakness, calf pseudohypertrophy, elevated CK levels and eventual cardiomyopathy2,3. Delayed diagnosis usually results from atypical clinical presentation, absent family history and reassuring neurological exam.

Design/Methods N/A

Results An 8 yo boy presented with a 4 year history of episodic exercise-induced myalgia with high intensity or prolonged activity without second-wind phenomenon. His previous medical and developmental history were unremarkable. Weight was 98th percentile-for-age and height was 85th percentile-for-age. General exam notable for single hyperpigmented macule on his lower back and mild scoliosis. Neurological examination was unremarkable. Labs notable for serum CK > 16,538 (normal 50-200 U/L), ALT 186 (normal 15-50 U/L), AST 295 (normal 15-50 U/L), and aldolase 18.3 (normal < 14.5 U/L). Full gene sequencing identified a hemizygous c.1724T>C change resulting in an amino acid substitution of leucine to proline at codon 575. Parental testing revealed maternal carrier status.

Conclusions This specific mutation has been described in only several cases with similar phenotypic presentations of exertional myalgia, muscle cramps, intermittent rhabdomyolysis, and normal developmental and neurological exam1,4-8. Our patient did not have associated cardiac, endocrine, orthopedic, or cognitive complications as seen with classic DMD although remains early in his diagnosis2. Long-term prognosis and life expectancy with this mutation is unknown. The early diagnosis of DMD is important for future pregnancies to estimate the risk of having the child with same mutation and help with future family genetic counseling.

Authors/Disclosures
Anastasia Railean, MD PRESENTER	Dr. Railean has nothing to disclose.
Jaclyn Martindale, DO, FAAN (Wake Forest Medical Center)	Dr. Martindale has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Movement Disorder Society. The institution of Dr. Martindale has received research support from Tourette Association of America. The institution of Dr. Martindale has received research support from American Board of Neurology and Psychiatry.

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