Case Study:

A 53-year-old banker, presents to the ER on Saturday evening complaining of persistent left shoulder, arm and neck pain that started in the morning. The pain started during a "pickup football game" with some friends that morning. He concedes that he may have "run around a bit more than he was used to" and "probably pulled some muscles" in his arm and neck. He has tried different positions, heat, Acetaminophen and ibuprofen to alleviate the pain without success. The pain has worsened throughout the day and now is bad enough that he feels "weak and sweaty".

He is mildly diaphoretic ("sweaty") but not in obvious distress. His vital signs are stable except for a mild tachycardia (fast heart beat) of 123 beats per minute. There is no tenderness to palpitation of his arm and neck muscles and there is full range of motion at all of the joints. His lungs are clear, his abdomen soft without tenderness and while there was tachycardia on cardiac examination, no murmurs were heard.

Laboratory examination revealed:

Blood Count: normal

Electrolytes: normal

Urinalysis: normal

Cardiac Troponins (T and I) I 15 mg/L; T 0.6 mg/L (nl: I < 10 mg/L; T 0-0.1 mg/L)

Total Creatine Kinase (CK) 4,552 U/L (nl:<190)

MB fraction comprising 18% of the total (nl: 4-6%)

1. What is your diagnosis?

2. How do you explain the location of his pain?

3. What additional studies should you use to confirm your diagnosis?

4. How did the creatine kinase isoenzymes help in your diagnosis?

5. Explain the biochemistry of these isoenzymes?

© Dr. Noel Sturm 2014

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