				Using the search form

CASE OF THE MONTH

Diagnostic challenges from your case files

Erich Fogg, PA-C, MMSc, department editor; Michael Burney, EdD, PA-C; Steven Reynolds, DO

CASE

The patient is a previously healthy 21-year-old man who came to the clinic complaining of fever, malaise, and significant myalgia for 7 days. He reported nausea and decreased appetite but no vomiting. Four days before this visit, he was feeling better and took a business trip, but his symptoms returned when he arrived home. He denied abdominal pain, stiff neck, photophobia, and skin rashes. He reported a low-grade fever of 100°F with intermittent sweating and body aches, primarily in the legs. For the past 2 to 3 days, he has had occasional diarrhea. He denied any recent flu vaccine or upper respiratory infection or pharyngitis over the past 3 months. He had had no recent contact with anyone who was ill.

History The patient reported no significant medical or surgical history. The family history was also unremarkable except for myocardial infarction at age 43 in his maternal grandfather.

The patient's current medications included pseudoephedrine (Sudafed), acetaminophen (Tylenol), and Nyquil. He had no known drug allergies. He reported no vision changes but said that there was some pain in his ears on the airplane during his business trip. Although his throat was not sore now, he did have a sore throat at the beginning of this illness. He denied melena or bright red blood per rectum and hematuria, although he did notice that his urine had darkened, which he attributed to drinking apple juice. He also denied any recent snake or insect bites and any drug or alcohol use.

Physical exam The patient was pale and appeared ill, but he was well developed and well nourished and in no acute distress. Vital signs were as follows: temperature, 103.3°F; pulse, 117 beats per minute; respirations, 20 breaths per minute; BP, 122/56 mm Hg; Sao₂, 99% on room air. The patient was alert and oriented and had normal strength and sensation. Heart rate and rhythm were regular with no murmurs. On the pulmonary exam, decreased breath sounds were noted in bilateral bases with poor inspiratory effort. The abdomen was flat, soft, and nontender with no hepatosplenomegaly and normoactive bowel sounds. The extremities were free of clubbing, cyanosis, and edema; the nail beds were noted to be slightly dusky. The skin was pale but warm.

Tests The CBC results were as follows: WBCs, 17.6 X 10⁹/L; hemoglobin, 12.1 g/dL; hematocrit, 35.1%; platelets, 205,000 cells/mm³; 89% neutrophils; and 6% lymphocytes. Chemistry findings were sodium, 133 mEq/L; potassium, 3.7 mEq/L; chloride, 99 mEq/L; bicarbonate, 25 mEq/L; BUN, 14 mg/dL; creatinine, 0.9 mg/dL; glucose, 118 mg/dL; albumin, 2.9 g/dL; total protein, 6.5 g/dL; aspartate aminotransferase, 1,007 U/L; alanine aminotransferase, 169 U/L; total bilirubin, 0.4 mg/dL; alkaline phosphatase, 48 U/L. The hepatitis A and B panels came back negative. The creatine phosphokinase (CPK) was 125,690 U/L with an MB fraction of 2.7%; troponin I was less than 0.2 ng/ml. Urine myoglobin was 16 mg/L (normal range, 0-15 mg/L, with usual results less than 1 mg/L). The monospot test was negative. Arterial blood gases on room air showed a pH of 7.44, Pco₂ of 37 mm Hg, Po₂ of 126 mm Hg, and Sao₂of 99%. A dipstick urinalysis revealed specific gravity of 1.015, large blood, 2+ protein, no WBCs, and 21 RBCs per high-power field on microscopic examination. A chest radiograph showed a large left lower-lobe infiltrate. An ECG showed normal sinus rhythm at 98 beats per minute, with no acute changes.

WHAT IS THE CAUSE OF THIS PATIENT'S RHABDOMYOLYSIS?

Infectious
Environmental
Immunologic

DISCUSSION

This patient had rhabdomyolysis secondary to community-acquired pneumonia. He was treated aggressively in the hospital with IV fluid hydration with normal saline. He was given mannitol, 25 g in 25% solution times one, and furosemide (Lasix), 20 mg times one. His fluid intake and output were carefully monitored. He was also given sodium bicarbonate with every liter of IV fluid to alkalinize the urine to optimize the creatinine secretion and to keep his urine pH greater than 7.5. The patient's CPK levels were monitored daily. On hospital day 1, the CPK level was 125,690 U/L; then it rose to a peak of 284,650 U/L before dropping to 20,000 U/L on the day of discharge. Three weeks after discharge, the CPK was 1,899 U/L (normal range, 7-13 U/L). Five weeks after discharge, it returned to normal levels.

The patient was also started on IV cefuroxime and doxycycline in the hospital, and gradually he improved, clinically and radiographically. Titers for Mycoplasma pneumoniae were negative.

On admission to the hospital, the patient's urine was dark brown, which is consistent with myoglobinuria. A nephrologist advised aggressive hydration as the primary treatment, with urine output at 200 to 300 cc/h. As the CPK counts started dropping, the IV fluid rate was gradually tapered. At no time during the course of the illness were the patient's BUN and creatinine elevated above normal limits. This is remarkable given that the majority of patients with elevated CPK levels and myoglobinuria will develop a degree of renal compromise. This patient resumed normal activities after he was discharged from the hospital.

Dr. Burney is Chair, Department of Health Sciences, and Associate Professor of Physician Assistant Education, Western University of Health Sciences, Pomona, Calif, and staff physician assistant, Seal Beach Family Medical Group, Seal Beach, Calif. Dr. Reynolds is Chair, Department of Family Practice, Miller Children's Hospital, Long Beach Memorial Medical Center, Long Beach, Calif, and staff physician, Seal Beach Family Medical Group. The authors have indicated no relationships to disclose relating to the content of this article. Mr. Fogg is Assistant Professor in and Program Director of the Physician Assistant Program at the College of Health Professions, University of New England, Portland, Me.