Influenza H1N1 Can Hurt Muscles Bad

Abstract & Commentary

By Joseph F. John, MD, Associate Chief of Staff for Education, Ralph H. Johnson Veterans Administration Medical Center; Professor of Medicine, Medical University of South Carolina, Charleston. Dr. John is a consultant for Cubist, Genzyme, and bioMerieux, and is on the speakers bureau for Cubist, GSK, Merck, Bayer, and Wyeth. This article originally appeared in the December 2009 issue of Infectious Disease Alert. At that time it was reviewed by Connie Price, MD, Assistant Professor, University of Colorado School of Medicine; she reports no financial relationship to this field of study.

Source: Ayala E, et al. Rhabdomyolysis associated with 2009 influenza H1N1. JAMA 2009;302:1863-1864.

It has been known for decades that influenza viruses have a propensity to affect muscle. Muscle aches from mild to severe occur regularly with the acute attack of the virus. I can remember as a young resident being so sore that I had to be rolled over and back during the first few days of influenza illness.

In the most recent issue of JAMA, filled with reports of H1N1 from North America, a short letter to the editor from Stanford University Medical Center highlighted the versatility of 2009 H1N1.

The patient in question is a 28-year-old influenza survivor who had 1 week of shortness of breath, muscle aches, and fever. Her pulse oximetry on presentation was 80% on room air. Her WBC was only 2800/mL, the LDH was 1875 U/L, and the creatine kinase (CPK) was a massive 27,820 U/L (normal 13-156). There was hemoglobin in the urine and infiltrates on the chest radiograph.

The patient had to be intubated but was able to be treated with oseltamivir and broad-spectrum antibacterials. A bronchoscopic exam revealed very friable hyperemic mucosa. The BAL fluid, when cultured at the California state lab, grew influenza A 2009 H1N1. With intensive critical care, the CPK decreased from 27,820 to 18,000 on day 2 to 3,000 on day 4, and then normalized. She was removed from mechanical ventilation on day 15 and discharged to home at day 18.

Commentary

It would be ideal to know how many patients with 2009 H1N1 have major muscle involvement. My clinical impression is that it occurs in < 1% of patients who have seasonal influenza. A 2005 Japanese study of patients with influenza pneumonia placed the value much higher (9.3%), though only 63 patients were studied (Nihon Kokyuki Gakkai Zashi 2005;43:731-735). Yet, for a disease that affects millions of patients per year, even 1% of 1 million is 10,000. When the year of novel influenza ends, perhaps we can get a better idea of the real prevalence.

Whatever the attack rate upon muscle, rhabdomyolysis is a real phenomenon that should fix the attention of providers when they see patients with severe influenza. In the Stanford patient, the CPK returned to normal quickly, but she still needed intubation and critical care to survive. The ability to diagnose 2009 H1N1 by viral culture resided in the Public Department of California Health, a testimony to our public health systems that have stepped up to the plate to help document strains of this season's influenza viruses. Culture from fluid obtained by BAL is a caveat of the present case, particularly since the nasopharyngeal sample was negative by PCR.

We await further descriptions of known and unknown complications as we watch the 2009 H1N1 pandemic progress. Influenza remains a disease that can humble clinicians. Yet to quote a recent poem by the illustrious physician poet Jack Coulehan, "The grace of humility is a precious gift."