C-reactive protein levels normalise quickly, but most patients still have symptoms after treatment.

Cellulitis is both very common and very commonly misdiagnosed: recent studies have shown that 30 to 60% of patients with presumed cellulitis actually have something else (NEJM JW Gen Med Apr 15 2023 and J Hosp Med 2023; 18: 254-261). That confusion has muddied clinical expectations for patients who really do have cellulitis – how quickly should these patients respond to therapy?

British researchers tabulated responses to treatment among 247 adults (mean age, 52 years; 67% men) with confirmed lower-extremity cellulitis who were enrolled in a treatment trial of seven to 10 days of a beta-lactam drug, with or without clindamycin. Between baseline and day five, surface area of affected skin shrank by 34%; by day 10, the affected area had shrunk by about 55%. Swelling lessened by almost 50% by day 10, but many patients still had substantial swelling, and the affected leg remained warmer than the unaffected one for most patients. More than half of patients continued to report discomfort in the affected leg at day 10, with pain scores above 5 (out of 10) reported by 14%. On the other hand, C-reactive protein levels fell dramatically during treatment, reaching near-normal levels in all patients by day 10.

Comment: I would have liked to see some data on diabetes and other comorbidities among the participants in this study and somewhat longer follow up. Still, the data deliver an important message: full clinical improvement in lower-extremity cellulitis takes time, and residual erythema, warmth and swelling after a course of antibiotics are the rule, not the exception. We should not presume treatment failure and treat again, but reassure the patient and monitor the leg.

Abigail Zuger, MD, Former Associate Clinical Professor of Medicine, Division of Infectious Diseases, Icahn School of Medicine at Mount Sinai; former Senior Attending Physician, Mount Sinai Roosevelt and Mount Sinai St. Luke’s Hospitals, New York City, USA.

Williams OM, et al. The natural history of antibiotic-treated lower limb cellulitis: analysis of data extracted from a multicenter clinical trial. Open Forum Infect Dis 2023; 10: ofad488.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Hospital Medicine.