What are the possible causes of a circular wound approximately the size of a dime that has remained unchanged for three months?

Differential Diagnosis of a Non-Healing Circular Wound

A circular wound the size of a dime that has not healed after 3 months meets the definition of a chronic wound and requires systematic evaluation for underlying causes including cutaneous leishmaniasis, diabetic ulceration, peripheral vascular disease, chronic infection (including atypical organisms), malignancy, or pyoderma gangrenosum. 1

Primary Diagnostic Considerations

Cutaneous Leishmaniasis

• Cutaneous leishmaniasis characteristically presents as a circular, non-healing ulcer that persists for months, often with raised borders and central ulceration 2
• The lesion typically begins as a papule that evolves into an ulcer over weeks to months, with the healing process potentially taking 3-12 months even with treatment 2
• Geographic exposure history is critical—consider this diagnosis if the patient has traveled to endemic areas (Middle East, Central/South America, Mediterranean region) 2
• Diagnosis requires tissue biopsy or scraping from the ulcer border for parasitologic examination 2

Diabetic Foot Ulcer (if located on lower extremity)

• Any ulcer that fails to heal after 6 weeks of appropriate care and off-loading should raise suspicion for underlying complications including infection, ischemia, or osteomyelitis 2
• Assess for loss of protective sensation using 10-g monofilament testing at multiple plantar sites 2
• Measure ankle-brachial index (ABI); values of 0.50-0.90 indicate mild-to-moderate peripheral vascular disease, while <0.50 suggests ischemia that will impair healing 2
• Probe the wound with a sterile blunt metal probe—if bone is palpable (characteristic stony feel), osteomyelitis is highly likely 2

Vascular Insufficiency

• Arterial insufficiency prevents adequate oxygen delivery (tissue oxygen pressure should be ≥30 mm Hg for healing) 2
• Venous insufficiency causes chronic edema and tissue breakdown, typically on the lower legs 3
• Transcutaneous oxygen pressure (TcpO2) measurement can guide assessment of tissue perfusion adequacy 2

Chronic Infection

• Wounds with persistent infection will not heal regardless of other interventions 2
• Obtain deep tissue specimens (not superficial swabs) for culture before initiating antibiotics, as superficial swabs yield contaminants and miss deep flora 2
• Consider atypical organisms including mycobacteria, fungi, or parasites if standard bacterial cultures are negative 2
• Anaerobic organisms may be present and require specific culture techniques 2

Malignancy

• Basal cell carcinoma, squamous cell carcinoma, or melanoma can present as non-healing ulcers 2
• Any wound that fails to show 50% reduction in size after 4 weeks of appropriate management warrants biopsy to exclude malignancy 2
• Marjolin ulcer (malignant transformation in chronic wounds) should be considered in long-standing ulcers 3

Pyoderma Gangrenosum

• Presents as painful ulcers with violaceous, undermined borders 3
• Often associated with inflammatory bowel disease, rheumatoid arthritis, or hematologic malignancies 3
• Diagnosis is clinical and by exclusion of other causes 3

Systematic Evaluation Approach

Initial Assessment

• Measure and document wound dimensions, depth, presence of undermining, quality of wound bed (granulation vs. necrotic tissue), and characteristics of wound edges (rolled, undermined, or flat) 2
• Assess surrounding skin for erythema, induration, warmth, or lymphangitic streaking suggesting active infection 2
• Probe the wound depth and check for communication with deeper structures, foreign bodies, or palpable bone 2

Laboratory and Imaging Studies

• Obtain deep tissue culture (not swab) if infection is suspected 2
• Plain radiographs to evaluate for osteomyelitis, foreign bodies, or gas in tissues 2
• MRI is most specific for detecting osteomyelitis and can identify deep abscesses, sinus tracts, or muscle involvement 2
• Consider biopsy for histopathology and special stains if diagnosis remains unclear after initial workup 2

Risk Factor Assessment

• Diabetes, immunosuppression, peripheral vascular disease, malnutrition, smoking, and certain medications (steroids, NSAIDs, chemotherapy) all impair wound healing 4, 5
• Assess glycemic control in diabetic patients—poor glucose control directly impairs healing 2
• Evaluate nutritional status including protein stores 4
• Review medication list for agents that impair healing (corticosteroids, immunosuppressants, anticoagulants) 4, 5

Management Principles

Wound Preparation

• Debride necrotic tissue and callus, as this removes bacterial burden and allows proper wound assessment 2
• Copious irrigation with sterile normal saline using adequate pressure 2
• Address any underlying infection with appropriate systemic antibiotics based on culture results 2

Addressing Underlying Pathology

• Healing cannot occur if the underlying cause is not corrected—no amount of wound care will overcome untreated ischemia, uncontrolled diabetes, persistent infection, or continued pressure 2, 3
• Revascularization procedures for ischemic wounds 2
• Strict glucose control for diabetic ulcers 2
• Off-loading for pressure-related wounds 2

Advanced Therapies

• If a wound fails to show 50% reduction in size after 4 weeks of appropriate standard care, consider advanced wound therapies including negative-pressure therapy, bioengineered tissues, or growth factors 2, 3
• Surgical intervention may be required for debridement, drainage of abscesses, or resection of infected bone 2

Critical Pitfalls to Avoid

• Do not assume all non-healing wounds are simply "chronic wounds"—each has an underlying cause that must be identified and addressed 3
• Do not rely on superficial wound swabs for culture—they are contaminated with colonizing flora and miss deep pathogens 2
• Do not continue the same treatment approach beyond 4 weeks without reassessment if the wound is not improving 2, 3
• Do not overlook the need for biopsy—malignancy and unusual infections require tissue diagnosis 2, 3
• Do not treat with antibiotics alone if surgical debridement or drainage is needed—antibiotics cannot penetrate necrotic tissue or closed abscesses 2