Patient Presentation
A 15-year-old male came to clinic in the morning for his health supervision visit. He was a basketball player and runner and was at the end of the basketball season and would be starting track soon. He had had no specific injuries and was doing well in school. The past medical history showed no athletic injuries, fainting, passing out, or palpitations. The family history was negative for neurological and rheumatologic problems. The review of systems was negative.

The pertinent physical exam showed a thin adolescent male with normal vital signs and mild comedomal acne. His musculoskeletal exam had normal strength and tone, and his neurological examination was also normal. The diagnosis of a healthy male was made. The patient went to the laboratory to have routine screening laboratories done including a hemoglobin/hematocrit and lipids. The laboratory evaluation was all normal, but a creatine kinase (CK) had been done inadvertently and was elevated at 420 U/L (normal 60-400 U/L). The physician called the patient that afternoon who confirmed that he wasn’t having any muscle pain, and had been drinking well during the evening before and at breakfast before the lab testing earlier. He also confirmed a normal basketball practice last evening and denied any trauma. The pediatrician felt that this was most consistent with CK elevation due to exercise, but wasn’t sure how long it took for CKs become normal after exercise. Repeat testing 2 weeks later during a break between athletic seasons showed a CK of 148 U/L on a morning blood sample.

Discussion
Acute rhabdomyolysis is an emergency that can cause acute renal failure (especially acute tubular necrosis caused by myoglobinemia) and electrolyte abnormalities. Common presenting findings are dark urine, myalgia and muscle weakness. Milder episodes can go unnoticed. Acute exertional rhabdomyolysis or unrecognized muscle injury can occur in underconditioned persons and even trained athletes who increase their exertion or exercise. Being unaccustomed to the ambient conditions such as heat, humidity and sun can also increase fluid loss and the risk of muscle injury. An overview and differential diagnosis of rhabdomyolysis can be found here.

Learning Point
Laboratory testing for rhabdomyolysis includes CK which is often used as a marker for myoglobinemia. CK remains elevated for relatively long periods of time and has slower elimination characteristics than myoglobin. Some data from military recruits and athletes has shown that CK and myoglobin increase especially at the beginning of an exercise programs but also remains elevated with ongoing exercise. Therefore, it is reasonable to conclude that this patient’s CK elevation was due to his exercise.

CK caused by rhabdomyolysis usually rises within 12 hours, peaks at 24-36 hours and then decreases 35-40% per day. Therefore levels that are not decreasing after the appropriate time indicate continued insult.

Questions for Further Discussion
1. What causes hematuria?
2. What causes proteinuria?

Related Cases

Disease: Muscle Disorders

Symptom/Presentation: Abnormal Laboratory Test | Health Maintenance and Disease Prevention

Specialty: Pathology | Orthopaedic Surgery and Sports Medicine

Age: Teenager

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Muscle Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

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Thomas BD Jr, Motley CP. Myoglobinemia and endurance exercise: a study of twenty-five participants in a triathlon competition. Am J Sports Med. 1984 Mar-Apr;12(2):113-9.

Update: Exertional rhabdomyolysis, active component, U.S. Armed Forces, 2011. MSMR. 2012 Mar;19(3):17-9.

Lappalainen H, Tiula E, Uotila L, Manttari M. Elimination kinetics of myoglobin and creatine kinase in rhabdomyolysis: implications for follow-up. Crit Care Med. 2002 Oct;30(10):2212-5.

Quinlivan R, Jungbluth H. Myopathic causes of exercise intolerance with rhabdomyolysis. Dev Med Child Neurol. 2012 Oct;54(10):886-91.

Muscal E. Rhabdomyolysis Workup. eMedicine.
Available from the Internet at http://emedicine.medscape.com/article/1007814-workup#aw2aab6b5b2 (rev. 4/24/14, cited 3/10/15).

Author

Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital