What is the diagnosis, workup, management, and treatment of primary and secondary skin lesions according to Nelson's Pediatrics?

Primary and Secondary Skin Lesions: Diagnosis, Workup, Management, and Treatment

Initial Diagnostic Approach

The diagnosis of skin lesions begins with systematic documentation of lesion morphology, location, distribution, and assessment for red-flag features including bleeding, pain, thickness, rapid growth, or ulceration. 1

Essential History Components

• Document sun exposure history and location of lesions, particularly noting if they occur in sun-exposed areas 1
• Identify immunosuppression status, as this significantly increases skin cancer risk and infection susceptibility 1
• Assess for previous skin cancer history, which confers a 4-8% risk of developing new primary melanoma within 3-5 years 1
• Evaluate medication history, particularly long-term steroid use which impairs wound healing and increases infection risk 2
• Review radiation therapy history, as this causes tissue damage and vascular compromise affecting healing 2

Physical Examination Framework

Primary lesions are the initial manifestations of disease and include macules, papules, plaques, nodules, vesicles, bullae, pustules, wheals, and cysts 3

Secondary lesions develop from primary lesions or external trauma and include scales, crusts, erosions, ulcers, fissures, excoriations, lichenification, and scars 3

Age-Specific Distribution Patterns

• Infants: Lesions typically appear on cheeks, scalp, and extremities; diaper area involvement rarely represents atopic dermatitis 4
• Older children and adults: Flexural areas (antecubital and popliteal fossae), head, and neck are common sites 4

Workup and Diagnostic Testing

When to Biopsy

Biopsy is indicated for lesions with diagnostic uncertainty, red-flag features (bleeding, pain, rapid growth, ulceration), or failure to respond to appropriate therapy. 1

Biopsy Technique for Suspected Melanoma

• Excisional biopsy is the preferred method with a 1-3mm margin to avoid transecting the lesion 1
• Avoid partial biopsies in suspected melanoma, as they lead to understaging and treatment delays 1

Immunocompromised Patients

In immunocompromised patients, biopsy or aspiration should be implemented as an early diagnostic step to obtain material for histological and microbiological evaluation. 5

• The differential diagnosis must include bacterial, fungal, viral, and parasitic agents 5
• Consider non-infectious etiologies: drug eruption, cutaneous infiltration with malignancy, chemotherapy/radiation-induced reactions, Sweet syndrome, erythema multiforme, leukocytoclastic vasculitis, and graft-versus-host disease 5
• Submit biopsy specimens for thorough cytological/histological assessment, microbial staining, and cultures 5

Management of Secondary Bacterial Infections

Topical Therapy

Topical antibiotics should be considered as primary therapy for secondary bacterial skin infections, as they provide high antibiotic concentration at the infection site while avoiding systemic allergic reactions. 6

• Mupirocin ointment: Apply a small amount to affected area three times daily; may cover with gauze dressing 7
• Re-evaluate patients not showing clinical response within 3-5 days 7

Systemic Therapy Indications

When systemic therapy is indicated, use penicillinase-resistant semi-synthetic penicillins, first-generation cephalosporins, macrolides, or combination antibacterials (amoxicillin/clavulanate, trimethoprim/sulfamethoxazole). 6

• Most secondary infections are polymicrobial, commonly including Staphylococcus aureus and Streptococcus pyogenes 6
• Culture affected lesions to guide therapy, particularly in atopic dermatitis where S. aureus superinfection is common 4

Management of Specific Conditions

Atopic Dermatitis

First-line management includes trigger avoidance, skin hydration, and topical steroids. 4

Lesion Evolution

• Acute lesions: Erythematous papules with serous exudates 4
• Subacute lesions: Erythematous scaling papules and plaques 4
• Chronic lesions: Lichenified with accentuated skin markings and hyperpigmentation 4

Critical Complications

• Monitor for eczema herpeticum from herpes simplex virus, which can be life-threatening 4
• Staphylococcal superinfection is common; obtain cultures to guide antibiotic selection 4

Vitiligo (Example of Benign Condition)

In children with skin types I-II, consider no active treatment initially other than camouflage cosmetics and sunscreens after discussion with family. 5

• Classical presentations can be diagnosed in primary care, but atypical presentations require dermatologist evaluation 5
• Assess psychological and quality-of-life effects in children 5
• Offer psychological interventions and parental counseling to improve coping mechanisms 5

Referral Criteria

Urgent specialist referral is required for lesions with red-flag features: bleeding, pain, rapid growth, thickness, or ulceration. 1

Follow-up Surveillance

• Stage 0 melanoma (in situ): Every 6-12 months for 1-2 years 1
• Stage IIB and higher: Every 3-6 months for 2 years 1
• Patients with previous skin cancer: Regular full-body skin examinations 1

Common Pitfalls to Avoid

• Do not rely solely on clinical appearance in immunocompromised patients; early biopsy is essential 5
• Do not perform partial biopsies on suspected melanomas 1
• Do not delay re-evaluation if topical antibiotics fail within 3-5 days 7
• Do not overlook systemic disease markers; rashes and lesions can indicate underlying conditions 8
• Do not assume diaper area rash in infants is atopic dermatitis; consider alternative diagnoses 4