The Growing Problem of Pseudocellulitis
ABSTRACT: Since prompt identification and treatment of cellulitis is critical, primary care physicians should be familiar with the condition and know when to reach out to a specialist for assessment to provide the patient with the most effective and cost-efficient treatment.
Cellulitis is a deep skin and subcutaneous fat infection characterized by poorly demarcated erythema, swelling, warmth, and tenderness. It most commonly affects the legs and is usually caused by streptococcal infections, though both methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MRSA) cellulitis are increasing in frequency.1-3
In the United States, cellulitis accounted for 10% of infectious disease-related hospitalizations from 1998 to 2006 and results in 14.2 million ambulatory care visits per year in the United States with an estimated annual cost of $3.7 billion.4,5
Prompt identification and treatment of cellulitis is critical, as cellulitis has been known to result in complications such as bacteremia, lymphadenitis, glomerulonephritis, endocarditis, and elephantiasis verrucosa nostra, among others.
In addition, failure to properly identify and treat mimickers of cellulitis can also result in failure to improve or recrudescence of symptoms, warranting hospital readmissions, as was noted in our hospital where cellulitis was the 15th most common cause of hospital admission to 1 medical unit and the number 1 cause of readmission within 30 days of discharge. Antibiotic use can be complicated by minor or severe allergic reactions as well as secondary problems, such as Clostridium difficile infections. In a climate of healthcare reform and heightened attention to patient safety, readmission, and complications of medications (including hospitalization) are additional factors highlighting the importance of accurate and prompt diagnosis and treatment of cellulitis.
Despite the common nature of this disease, no gold standard diagnostic technique exists since as radiologic and microbiologic testing has not proved reliable. Diagnosis rests on clinical examination and diagnostic criteria that are poorly defined and variably applied. Even features such as fever or leukocytosis, thought to be objective markers of cellulitis, are in practice rarely found in most cases of true infection.
Further complicating the issue, the tetrad of key physical findings rubor, dolor, calor, and tumor that are taught in medical school are in actuality nonspecific markers of inflammation. As a result, there are many diseases that clinically mimic cellulitis, known as pseudocellulitides.
Pseudocellulitides
The clinical similarity of these pseudocellulitides to actual cellulitis has resulted in misdiagnosis rates estimated to be as high as 28% in some American hospitals and even higher in the outpatient setting.6,7 Additionally problematic is the fact that the rates of MRSA-related soft tissue infections nearly doubled from 1998 to 2004, possibly due to the empiric use of antibiotics for suspected skin infections.8 Mimicking conditions include stasis dermatitis, deep vein thrombosis, thrombophlebitis, erythema migrans, gout, contact dermatitis, hematoma, and many others; stasis dermatitis is the most commonly cited cause of pseudocellulitis, often misdiagnosed as the ever-common “bilateral cellulitis.”
In the absence of trauma to both legs, however, bilateral cellulitis is exceedingly rare and stasis dermatitis is the far more likely diagnosis. Unfortunately, patients with stasis dermatitis who are hospitalized with a suspected bilateral cellulitis and treated with antibiotics likely improve clinically because of the leg elevation associated with being bedridden rather than the actual antibiotic effect. It is this improvement, though, that subsequently serves to “confirm” the misdiagnosis and thereby propagates the problem.
The Derm Advantage
Primary care practitioners should refer patients to a dermatologist to accurately distinguish cellulitis from pseudocellulitides.6 A British study using a dermatologist assessment of 635 patients referred for admission in cases of suspected lower limb cellulitis found that 210 patients (33%) had alternate diagnoses which did not require hospitalization, and 96% of patients with true cellulitis were managed as outpatients, many at home.9 In addition, 28% of true cellulitis patients had an underlying skin disease that predisposed them to recurrent cellulitis such as leg ulceration or lymphedema, which once identified could be treated, reducing the risk of repeat infections.9 Of all patients presenting with a concern for lower extremity cellulitis, only 18 (3%) actually had cellulitis that required hospital admission for conventional treatment.9
Of note, there were no statistically significant patient demographics, risk factors, or systemic signs of infection that could distinguish the cellulitis group from the pseudocellulitis group.9
These specialists have been shown to reduce antibiotic use in the outpatient setting. A recent study that used dermatologists to assess adult patients diagnosed with cellulitis by their outpatient primary care physician found that 83% of patients in the assessment group had a pseudocellulitis instead of true cellulitis.10
In addition, the group that was randomized to assessment by a dermatologist reported that antibiotic use was successfully reduced by 80% with no adverse events.10 Similar to pseudocellulitis among hospitalized patients, the main alternate diagnoses were eczematous dermatitis, stasis dermatitis, erythema migrans, and arthropod reactions.10 The large discrepancy in rates of cellulitis and antibiotic usage between the dermatologist-evaluated and control arm underscores the large number of conditions that resemble cellulitis and the potential benefit of dermatologist intervention in this particular group of patients.
Given that dermatologists are the physicians trained to identify all skin conditions, including cellulitis, it is logical that they would be best group to identify and treat skin diseases that mimic cellulitis. This is especially important when failing to appropriately diagnose some pseudocellulitides, such as erythema migrans, which can have devastating long-term consequences.
Cellulitis misdiagnosis is a significant problem in the inpatient, outpatient, and emergency medical settings. Because patients diagnosed with cellulitis are treated with at least 1 round of antibiotics, cellulitis misdiagnosis is especially pertinent in the existing medical system that is challenged by rising antibiotic resistance, adverse events, and healthcare costs.
There are no reliable statistical differences in identifying factors between groups with true cellulitis and mimickers that will predict who has true infection and who has a mimicking diagnosis. As such, internal and emergency medicine physicians, as well as primary care practitioners, should be educated on mimickers of cellulitis and taught to rely on the dermatologist assessment of suspected cases of cellulitis to more accurately diagnose patients and avoid inappropriate hospitalization and antibiotic use.
This article was originally published in the November 2014 issue of The Dermatologist.
References:
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10. Arakaki RY, Strazzula L, Woo E, Kroshinsky D. The impact of dermatology consultation on diagnostic accuracy and antibiotic usage among patients presenting with suspected cellulitis to outpatient internal medicine offices: a randomized-controlled trial. JAMA Dermatol. 2014;150(10):1056-1061.