Differences Between Eczema and Psoriasis
Eczema (atopic dermatitis) and psoriasis are distinct chronic inflammatory skin conditions with different pathophysiological mechanisms, clinical presentations, and treatment approaches.
Pathophysiology
Psoriasis
- Immune-mediated disorder characterized by inappropriate activation of T-cells and dendritic cells with subsequent release of inflammatory cytokines 1
- Results in keratinocyte hyperproliferation with cell turnover accelerated to approximately 4 days (versus normal 28 days) 2
- Strong genetic component with HLA-Cw6 allele (PSORS1) being the major susceptibility gene 1
- Primarily a Th1/Th17-mediated disease with TNF-α, IL-12, IL-17, and IL-23 playing key roles
Eczema (Atopic Dermatitis)
- Barrier dysfunction with impaired skin integrity
- Th2-dominant immune response with elevated IgE levels
- Often associated with personal or family history of atopy (asthma, allergic rhinitis)
- Environmental triggers play a significant role
Clinical Presentation
Psoriasis
- Well-demarcated, erythematous plaques with silvery scale 1
- Common locations: scalp, elbows, knees, presacral region 1
- Several clinical variants:
- Plaque (most common)
- Inverse (affects skin folds with minimal scale)
- Guttate (small, drop-like lesions)
- Pustular
- Erythrodermic (generalized erythema) 1
- Often non-pruritic or mildly pruritic
- Nail involvement in approximately 50% of cases (pitting, onycholysis, subungual hyperkeratosis) 1
Eczema (Atopic Dermatitis)
- Poorly demarcated, erythematous patches/plaques with serous exudate
- Common locations: flexural areas (antecubital and popliteal fossae), face, neck
- Intense pruritus is a hallmark feature
- Acute phase: vesicles, weeping, crusting
- Chronic phase: lichenification, excoriations
- Distribution varies with age (infants: face, extensor surfaces; adults: flexural areas)
Histopathology
Psoriasis
- Acanthosis (thickened epidermis)
- Parakeratosis (retained nuclei in stratum corneum)
- Munro microabscesses (neutrophils in stratum corneum)
- Elongated rete ridges
- Dilated blood vessels in papillary dermis
Eczema (Atopic Dermatitis)
- Spongiosis (intercellular edema)
- Less pronounced acanthosis
- Lymphocytic infiltrate
- Absence of neutrophilic microabscesses
Comorbidities
Psoriasis
- Psoriatic arthritis in approximately 30% of patients 1
- Cardiovascular disease and metabolic syndrome 1
- Inflammatory bowel disease
- Increased risk of lymphoma
- Depression and anxiety 1
Eczema (Atopic Dermatitis)
- Other atopic conditions (asthma, allergic rhinitis, food allergies)
- Sleep disturbances due to pruritus
- Increased risk of skin infections
- Mental health impacts (depression, anxiety)
Treatment Approaches
Psoriasis
- Topical therapies: corticosteroids, vitamin D analogs, calcineurin inhibitors
- Phototherapy: Narrowband UVB (more effective than broadband UVB) 1
- Systemic therapies: methotrexate, cyclosporine, acitretin
- Biologics: TNF-α inhibitors (adalimumab, etanercept), IL-12/23 inhibitors (ustekinumab), IL-17 inhibitors, IL-23 inhibitors 1
Eczema (Atopic Dermatitis)
- Topical therapies: corticosteroids, calcineurin inhibitors, barrier repair moisturizers
- Phototherapy: Narrowband UVB
- Systemic therapies: cyclosporine, methotrexate, azathioprine
- Biologics: dupilumab (IL-4/IL-13 inhibitor)
Diagnostic Challenges
- In approximately 20% of cases, features of both conditions may overlap, making diagnosis challenging 3
- Some patients may develop "paradoxical eczema" when treated with biologics for psoriasis 4
- The term "PsEma" has been proposed for cases with clinical, histologic, and therapeutic features of both conditions 3
Key Distinguishing Features
- Scale appearance: Silvery in psoriasis vs. serous crusting in eczema
- Border definition: Sharp in psoriasis vs. indistinct in eczema
- Pruritus intensity: Mild/moderate in psoriasis vs. severe in eczema
- Distribution: Extensor surfaces in psoriasis vs. flexural areas in eczema
- Nail involvement: Common in psoriasis, rare in eczema
- Koebner phenomenon: Present in psoriasis (development of lesions at sites of trauma)
Management Considerations
- Accurate diagnosis is essential for appropriate treatment selection
- Both conditions significantly impact quality of life and have psychosocial effects 2
- Treatment should address both skin manifestations and associated comorbidities
- Patient education about chronic nature of both conditions is important for long-term management