Review Question - QID 217188

A patient with unilateral warmth, swelling, and tenderness with risk factors of infection (diabetes, obesity), especially in the setting of low grade fever or other systemic symptoms should raise concern for cellulitis.

Cellulitis is a common bacterial infection of the skin that involves the lower dermis and subcutaneous tissue. It presents with erythema, swelling, and tenderness. Risk factors include immunosuppression (including poorly controlled diabetes), trauma (which results in breaks of the skin and penetration of bacteria), and obesity. It must be distinguished from an acute deep vein thrombosis, which may present similarly but would also have a positive Homan's sign, suggestive clinical history (e.g. solid tumor history, extended duration travel, recent hospitalization, immobility). Typically, cellulitis can be managed in the outpatient setting with oral antibiotics, but may occasionally require inpatient care with intravenous antibiotics depending on the patient's level of systemic symptoms and involvement. For instance, sepsis as a result of cellulitis would warrant inpatient admissions and intravenous antibiotics. Purulent cellulitis is due to Staphylococcus aureus whereas non-purulent cellulitis is typically due to Streptococcus pyogenes. This is a key branch point in management to discern the appropriate antibiotic choice.

Rrapi et al. discuss the pathogenesis, diagnosis, and treatment of cellulitis. 34059247

Figure/Illustration A demonstrates unilateral erythema with appreciable edema of the left lower leg with poorly defined edges of erythema (orange arrow).

Incorrect Answers:
Answer 2: Deep vein thrombosis may present with unilateral swelling and redness. However, warm and low-grade fever would be unusual. A positive Homan’s sign in the setting of risk factors for provoked or unprovoked thrombosis may be present.

Answer 3: Erysipelas is distinguished from cellulitis due to more superficial involvement, resulting in more sharply demarcated borders of erythema.

Answer 4: Necrotizing fasciitis patients often present septic, may have small bullae or vesicles present over the areas of involvement and marked pain out of proportion to exam. This condition is a surgical emergency.

Answer 5: Necrolytic migratory erythema is a red, blistering rash that is often around the mouth and distal extremities, symmetric/involving both sides of the body, and is associated with glucagonomas.

Bullet summary: Unilateral erythema, swelling, tenderness, and low-grade fever in the setting of appropriate risk factors for increased risk of infection (e.g. obesity) portend a diagnosis of cellulitis.