Up to 30 percent of suspected leg cellulitis cases turn out to be something else
Cellulitis, a bacterial infection of the deeper skin layers, is one of the commonest reasons for hospital admission. Yet it is surprisingly easy to get wrong. In the United States, misdiagnosed leg cases cause tens of thousands of needless hospital stays and hundreds of millions of dollars in avoidable spending every year.
The infection sits in the dermis and the fat beneath it, producing a red, hot, painful patch with blurred edges that spreads over a few days. Streptococci and Staphylococcus aureus are the usual culprits, often bacteria that live harmlessly on healthy skin until a break lets them in. On the leg, that break is typically a scrape, an insect bite or cracked skin between the toes; on the face, there often is no obvious wound. Its cousin erysipelas stays more superficial, with sharp borders and more frequent fever.
Diagnosis rests mostly on how the skin looks, because the bacteria can rarely be grown in the lab: organisms are identified in only about 15 percent of cases, and blood cultures come back positive in under 5 percent. That leaves room for mimics. A deep vein clot in the leg causes the same warmth, pain and swelling, stasis dermatitis from poor circulation looks similar, and Lyme disease can be mistaken for it when the classic bullseye rash is missing. Bedside ultrasound, which shows a cobblestone pattern in cellulitis, can separate it from an abscess and changed management in up to 56 percent of cases in one analysis.
Risk climbs with age, obesity, leg swelling, a weakened immune system and diabetes, which impairs both circulation and immunity and can leave foot ulcers numb and unnoticed. Oral antibiotics such as cephalexin are the standard approach, with alternatives for penicillin allergy or suspected MRSA, and an abscess usually needs draining. Around 95 percent of people improve within 7 to 10 days, although a course fails in between 6 and 37 percent of cases. Severe pain can signal necrotizing fasciitis, a rare deep infection and a medical emergency.
The global toll is large. About 21.2 million people had cellulitis in 2015, and deaths rose from 12,600 in 2005 to about 16,900 in 2016. In the United States the condition drives more than 650,000 admissions a year, and in the United Kingdom it accounted for 1.6 percent of hospital admissions.
Source: Cellulitis
