What is the next step in managing an elderly male patient with a history of MRSA, squamous cell carcinoma, psoriasis, and hypertension, who had a stroke resulting in left-sided hemiparesis, presenting with a 14-day history of a non-healing, red, swollen spot on his left foot, unresponsive to triamcinolone cream?

Management of Non-Healing Foot Lesion in High-Risk Patient

The next step is to obtain a tissue biopsy of the lesion to rule out malignancy (particularly squamous cell carcinoma recurrence) and exclude osteomyelitis, followed by bacterial culture to assess for MRSA infection. 1

Immediate Diagnostic Priorities

Why Biopsy is Critical

• The patient's history of squamous cell carcinoma makes malignancy a primary concern, especially given the 14-day duration without improvement on topical corticosteroids 1
• Non-blanching erythema with tenderness on the posterior calcaneus in an immobile limb (left-sided hemiparesis) raises concern for pressure-related tissue damage with potential deep infection or malignancy 1
• Triamcinolone failure after 14 days of twice-daily application strongly suggests this is NOT a corticosteroid-responsive dermatosis (psoriasis, eczema, or other inflammatory conditions would typically show some improvement within 2 weeks) 2, 3

Rule Out Osteomyelitis

• Any non-healing ulcer or lesion on the foot that persists beyond 6 weeks of appropriate care should raise suspicion for underlying osteomyelitis, particularly over bony prominences like the calcaneus 1
• The posterior calcaneus location is a classic pressure point in patients with limited mobility (left hemiparesis), making osteomyelitis a significant concern 1
• Plain radiographs of the left foot should be obtained immediately to look for bone destruction, though early osteomyelitis may not be visible 1
• If plain films are negative but clinical suspicion remains high, MRI is the most useful imaging modality for detecting early osteomyelitis 1

Assess for Deep Infection

• The patient's MRSA history significantly increases risk for complicated skin and soft tissue infection, particularly in an area with compromised perfusion from hemiparesis 1
• Obtain bacterial culture from the lesion (deep tissue culture if possible, not superficial swab) to identify MRSA or other pathogens 1
• Blood cultures should be drawn if there are any systemic signs (fever, elevated WBC, though vitals are currently stable) 1

Why This is NOT a Dermatologic Condition Requiring Continued Topical Therapy

Triamcinolone Failure Indicates Wrong Diagnosis

• Triamcinolone 0.1% is a medium-potency topical corticosteroid that should produce visible improvement in psoriasis, eczema, or other inflammatory dermatoses within 1-2 weeks 2, 4
• Complete lack of response after 14 days of twice-daily application effectively rules out corticosteroid-responsive conditions 2, 3
• Continuing or escalating topical corticosteroids without establishing a diagnosis risks masking infection or delaying cancer diagnosis 2

Red Flags Against Psoriasis Flare

• Psoriasis typically presents with well-demarcated plaques with silvery scale, not isolated tender erythema with mild edema 1
• Unilateral presentation on an immobile limb is atypical for psoriasis, which usually shows symmetric distribution 1
• The posterior calcaneus location over a pressure point in a hemiparetic patient suggests mechanical/ischemic etiology rather than autoimmune 1

Specific Diagnostic Algorithm

Step 1: Tissue Biopsy (Perform Within 48 Hours)

• Punch biopsy (4-6mm) or incisional biopsy of the lesion to obtain tissue for histopathology 1
• Send separate tissue sample for bacterial culture (aerobic, anaerobic, and fungal) 1
• Specifically request evaluation for squamous cell carcinoma, given the patient's history 1

Step 2: Imaging

• Plain radiographs of the left foot (AP, lateral, oblique views) to assess for bone involvement 1
• If radiographs show bone destruction or if clinical suspicion for osteomyelitis remains high despite negative films, proceed to MRI 1

Step 3: Laboratory Assessment

• Complete blood count with differential to assess for leukocytosis 1
• Inflammatory markers (ESR, CRP) are often elevated in osteomyelitis 1
• Blood cultures if any systemic signs develop 1

Critical Pitfalls to Avoid

Do NOT Continue Topical Corticosteroids

• Continuing triamcinolone or escalating to higher-potency steroids (like clobetasol) without a confirmed diagnosis risks worsening infection by suppressing local immune response 2, 5
• Topical corticosteroids can mask signs of infection and delay appropriate antimicrobial therapy 2

Do NOT Assume This is Psoriasis

• The patient's psoriasis history is a red herring in this context—the clinical presentation (isolated, tender, non-blanching lesion on pressure point in immobile limb, unresponsive to steroids) does not fit psoriasis 1
• Psoriasis does not typically present with isolated tender lesions that fail to respond to medium-potency topical steroids 1, 2

Do NOT Delay Biopsy for "Trial of Antibiotics"

• Empiric antibiotics without tissue diagnosis risks missing malignancy (squamous cell carcinoma can present as non-healing ulcers) 1
• If MRSA infection is suspected based on clinical appearance, culture should be obtained BEFORE starting antibiotics to guide targeted therapy 1

If Biopsy Shows Squamous Cell Carcinoma

• Surgical excision with clear margins is the definitive treatment 1
• The patient's history of squamous cell carcinoma and psoriasis treated with immunosuppressive agents increases risk for additional skin cancers 6

If Cultures Grow MRSA

• Vancomycin is first-line for complicated MRSA skin and soft tissue infections, particularly if osteomyelitis is confirmed 1
• Alternative agents include linezolid, daptomycin, or ceftaroline for MRSA coverage 1
• Duration of therapy: 2-4 weeks for soft tissue infection alone, 4-6 weeks minimum if osteomyelitis is present 1

If Osteomyelitis is Confirmed

• Parenteral antibiotics for 4-6 weeks are required, with consideration for oral switch once clinically stable 1
• Surgical debridement may be necessary if there is significant bone destruction or abscess formation 1
• Close monitoring for treatment failure, which may necessitate amputation in severe cases 1