Dermatologic Look-Alikes TABLE. Lichen Simplex Chonicus vs Psoriasis Lichen Simplex Chonicus1-7
Psoriasis8-17
Dermatologic presentation
• Circumscribed, pruritic, lichenified plaques • Scale • Excoriation • Hypo- or hyperpigmentation
• Well-demarcated erythematous or salmon-pink plaques • Silver or white scale
Characteristic location
• Head and neck • Genitals • Arms • Lower legs • Ankle flexures • Inner thighs
• Extensor surfaces of elbows and knees • Scalp • Umbilicus • Lumbosacral region
Epidemiology
• Adults aged 30-50 years • 2 times more common in women
• 2 age peaks: 15-20 years, 55-60 years • More severe in men
Potential risk factors
• Eczema, hay fever, asthma • Psychiatric disorders
• HLA-Cw6, CARD14 gene mutations • Infections, medications, trauma, comorbid conditions
Etiology
• Repeated scratching of a pruritic area • Itch-scratch cycle • Nerve proliferation • Linked to emotional stress
• Immune mediated • Prominent involvement of T-cells and cytokines (IL-12, IL-17, IL-23, and TNF-α)
Histology
• Epidermal hyperplasia with acanthosis • Dermal fibrosis • Streaked collagen bundles
• Parakeratosis, loss of granular layer, elongation of rete ridges, micropustules of Kogoj, and Munro microabscesses • Prominent dermal blood vessels • Leukocytic infiltrate
Diagnosis
• Clinical history and physical
• Clinical history and physical
Treatment
• Break the itch-scratch cycle • Topical corticosteroids • Topical emollients • Antihistamines • Reduction of stress
• Topical corticosteroids • Vitamin D derivatives • Calcineurin inhibitors • UV light therapy • Systemic therapy • Biologics
IL, interleukin; TNF, tumor necrosis factor; UV, ultraviolet
Histopathology of psoriasis is characterized by 3 main features: hyperplasia of the epidermis, prominent dermal blood vessels, and dermal inflammatory leukocytic infiltrate.16 Epidermal changes include parakeratosis, loss of the granular cell layer, regular elongation of the rete ridges, micropustules of Kagoj, and Munro microabscesses.16 Although laboratory abnormalities in psoriasis generally are nonspecific and not required for diagnosis, serum uric acid, C-reactive protein, sedimentation rate, and serum immunoglobulin A all may be increased.10 Diagnosis usually is made based on characteristic clinical features.10
Potential conditions to consider in the differential diagnosis of psoriasis include eczema, mycosis fungoides, lichen planus, pityriasis rosea, tinea infections, seborrheic dermatitis, syphilis, pityriasis lichenoides et varioliformis, candidiasis, Paget disease, and squamous cell carcinoma in situ.10,11,17 Psoriasis generally can be differentiated from other disorders based on clinical findings and patient history, but biopsy may be needed to confirm the diagnosis.10 In addition, the specific type of psoriasis must be distinguished from other types.17 Treatment of psoriasis is aimed at reducing symptoms and disease control. The majority of patients (70% to 80%) will
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