Cellulitis — Clinical Case (Wikimedia Commons)

Diagnosis: Cellulitis

Cellulitis following an abrasion. Note the red streaking up the arm from involvement of the lymphatic system.. Clinical photograph sourced from Wikimedia Commons (CC BY-SA 3.0). Attribution: James Heilman, MD.

Clinical Presentation

Expanding area of erythema, warmth, swelling, and tenderness without sharp borders. Unilateral in most cases. May have associated lymphangitis (red streaking), lymphadenopathy, and systemic symptoms (fever, malaise). Bullae or hemorrhagic changes indicate severe infection.

Clinical History

Portal of entry: skin break, tinea pedis, insect bite, wound, eczema. Risk factors: lymphedema, venous insufficiency, obesity, prior cellulitis, immunosuppression. Recurrence common (~20-30%) — address predisposing factors.

Treatment

Mild (no systemic symptoms): oral antibiotics (cephalexin, dicloxacillin; TMP-SMX + amoxicillin if MRSA risk). Moderate-severe: IV antibiotics (cefazolin, vancomycin if MRSA). Abscess: I&D ± antibiotics. Treat predisposing factors (tinea pedis, edema). Penicillin prophylaxis for recurrent episodes.

Differential Diagnosis

Deep vein thrombosis, Stasis dermatitis, Contact dermatitis, Erysipelas, Necrotizing fasciitis, Lipodermatosclerosis, Lymphedema

Key Learnings

Cellulitis is overdiagnosed — bilateral 'cellulitis' is almost always stasis dermatitis. Mark the border with pen to track progression. Necrotizing fasciitis red flags: pain out of proportion, crepitus, rapid progression, hemodynamic instability. Imaging (CT/MRI) if necrotizing fasciitis is suspected.

Tags: cellulitis, bacterial, infection, soft tissue, streptococcal