Pharmacology 2: Differential Diagnosis for Soft Tissue Infection

Cellulitis

Typically unilateral, affects deeper layers of the skin, warmth, mild edema

Bugs: Staph aureus, group A strep, group B strep

Abx: cephalexin, MRSA antibiotics

Erysipelas

Affects uppermost layers of the skin, superficial lymphatic system, bright red erythema, skin elevation, well-demarcated borders

Bugs: group A Strep (strep pyogenes)

Abx: penicillin

Necrotizing fasciitis

Rapidly developing infection of deep fascia, severe pain out of proportion to exam, swelling, bullae and necrosis, ± crepitus

Bugs: polymicrobial, Gram ± pathogens

Abx: surgical debridement followed by broad spectrum IV abx

Septic Arthritis

Suspect when cellulitis overlies a joint, joint swelling and warmth

Bugs: Staph aureus, strep

Abx: based on gram stain of synovial fluid

Gout

joint pain, repeated attacks, elevated serum uric acid level

Deep vein thrombosis (DVT)

can be difficult to distinguish from cellulitis and may necessitate venous duplex to rule out thrombus

Stasis dermatitis

Scaling, dryness, redness, presence of telangiectasia, varicose veins, hyperpigmentation, edema subsides with recumbency

Folliculitis

Superficial hair follicle infection with small pustules

Bugs: staph aureus

Abx: mupirocin/bactroban (localized), nafcillin or cephalexin (extensive)

Tinea

Fungal infection that shows as a ring-like pattern. capitis (head), corporis (body/ringworm), pedis (athlete’s foot)

Candida

Yeasty film looking fungal infection

Antifungal: nystatin, clotrimazole, fluconazole

Onychomycosis

Toenail fungus

Antifungal: terbinafine

Seborrheic dermatitis

Fungal infection of the scalp

Antifungal: ketoconazole