Pharmacist Knowledge About Differential Diagnosis of Lower Limb Cellulitis Can Impact Patient Health

Pharmacist Knowledge About Differential Diagnosis of Lower Limb Cellulitis Can Impact Patient Health

Differential Diagnosis of Lower Limb CellulitisWe’re all human and mistakes are an expected part of life, but when lower limb cellulitis is misdiagnosed—and it results in an estimated 50,000 to 130,000 unnecessary hospitalizations yearly—it’s time for all members of the health care community to step up to help alleviate the problem.

Pharmacists are in the position to counsel many of these patients, whether they self-treat before heading to the emergency department or they’ve consulted the family doctor and fill prescriptions for antibiotics. When you cross paths, you’ll make a significant difference by taking a few minutes to counsel about the differential diagnosis of lower limb cellulitis and refer them to a dermatologist.

High Costs of Misdiagnosed Lower Limb Cellulitis

The latest blockbuster news about misdiagnosed cases of lower limb cellulitis was published in the November 2016 issue of JAMA Dermatology, but this isn’t the first time the problem has been acknowledged. Back in 2011, a group from the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center published a study noting that 28 percent of patients hospitalized for cellulitis were misdiagnosed. The bad news is that the number of errors hasn’t improved since then. The 2016 study reported that one-third of the patients admitted for cellulitis were either discharged with a different diagnosis or their diagnosis was changed within one month following discharge.1

For the JAMA Dermatology study, investigators collected data from the medical records of all adult patients who were admitted to the hospital from the emergency department with a diagnosis of lower limb cellulitis. After excluding patients with an abscess, surgery, trauma, or recent intravenous antibiotics, they identified 259 patients who were admitted between June 2010 and December 2012.2 While hospital staff could rightfully choose to err on the side of caution, the costs incurred by misdiagnosed patients are shocking:

  • 85% of the patients did not need to be hospitalized.
  • 92 percent received unnecessary antibiotics.
  • $195 million to $515 million in avoidable health care spending—estimate based on the mean hospital stay of 4 days at a cost of $12,656.90 using the Medical Expenditure Panel Survey.
  • Projected nosocomial infections = 9,000
  • Projected C. difficile infections = 1,000 to 5,000

Differential Diagnosis Basics for Pharmacists

An editorial in the 2016 issue of JAMA Dermatology noted that dermatologists are under-consulted and needed to take a proactive role because it’s such a challenge to distinguish cellulitis from a mimicker.3 The well-being of many patients hangs in the balance, considering cellulitis leads to about 2.8 million emergency department visits every year and has an estimated prevalence of 14.5 million cases per year.4

Armed with basic knowledge of the problem, community pharmacists can intervene to counsel patients who may not have consulted a physician, educate them about the challenges of cellulitis, and encourage them to see a dermatologist. As you promote early and accurate diagnosis, you can help patients avoid complications of untreated bacterial infection, such as lymphangitis, bacteremia, endocarditis, and glomerulonephritis.

Key characteristics and symptoms of lower limb cellulitis:

  • Redness, warmth, tenderness, and swelling are the primary characteristics—the infection occurs in deep layers of the skin and subcutaneous tissue.
  • Cellulitis is rarely bilateral
  • Patients typically have systemic symptoms such as fever.
  • Often arises from a break in the skin.
  • Athletes foot, diabetes, and obesity are the most common, non-trauma causes.
  • History of trauma and pain in the affected area suggests cellulitis—the trauma may seem insignificant to the patient, such as a small cut, puncture wound, or an insect bite.
  • Chronic inflammation and a slowly progressive course indicate something other than cellulitis.

Skin conditions that mimic cellulitis include:

  • Stasis dermatitis – This is the most common mimic of cellulitis. It’s usually bilateral and not tender, has been ongoing for years, and presents with pitting edema, hyperpigmentation, serous drainage, and superficial desquamation. The cause is often chronic venous insufficiency.
  • Contact dermatitis – Allergic and irritant contact dermatitis are easy to mistake for cellulitis. Ask patients about changes in medications, soaps, new hobbies, or any activity that may trigger contact dermatitis. Be aware that nonhealing leg ulcers may arise when patients try to self-treat contact dermatitis with topical antibiotics or lubricants.
  • Lymphedema – Localized edema with secondary cutaneous changes such as dyspigmentation and hyperkeratosis. These patients usually have unilateral, nonpitting edema without any systemic symptoms. This condition is common in patients who are overweight or obese because excess weight obstructs inguinal lymphatics.
  • Papular urticaria – This is a dermal hypersensitivity reaction to an insect bite. Patients may have many smaller papules or large plaques that resemble cellulitis, but it is set apart by intense itching.
  • Lipodermatosclerosis – A sclerosing panniculitis that creates the appearance of an inverted bowling pin of the leg. In the acute phase, patients have inflammation, warmth, erythema, and pain, which makes it hard to distinguish from cellulitis. The chronic phase is characterized by plaques and the skin is often brown secondary to hemosiderin deposits.

You may be able to target patients who are purchasing OTC pain relievers or topical products to relieve inflammation or itching, but also keep the potential for cellulitis in mind when you dispense antibiotics. Skin conditions that are treated with antibiotics but fail to respond are red flags that the condition is not cellulitis—about 90 percent of cellulitis cases are cured with a course of antibiotics. Stay alert for other populations at higher risk for cellulitis, including young athletes (and their parents), patients purchasing medications and supplies for diabetes, and people with other diseases associated with cellulitis, such as lymphedema and osteomyelitis.

Promote Early and Accurate Diagnosis of Cellulitis

Many patients with a mild-to-moderate case of cellulitis will self-treat, which gives you the unique opportunity to intervene before they’re at risk for misdiagnosis. A poster placed along with a display of topical treatments could encourage customers to “ask the pharmacist” about any skin condition or provide a description of cellulitis. Every patient you counsel stands to gain an earlier or more accurate diagnosis, so they benefit from better health and you benefit from developing loyal customers.

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Show 4 footnotes

  1. “Diagnostic Accuracy in Patients Admitted to Hospitals with Cellulitis,” March 2011,
  2. “Costs and Consequences Associated with Misdiagnosed Lower Extremity Cellulitis,” November 2016,
  3. “Dermatologists Must Take an Active Role in the Diagnosis of Cellulitis,” November 2016,
  4. “Cellulitis,” August 2016,

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