Psoriasis Vulgaris

Detailed Overview

Plaque psoriasis is the most common variant of psoriasis, accounting for 80-90% of cases. It is a systemic inflammatory condition that not only affects the skin but is heavily associated with cardiometabolic comorbidities such as metabolic syndrome, cardiovascular disease, and psoriatic arthritis. The dysregulation of the adaptive immune system, particularly involving dendritic cells, T-cells, and the cytokines IL-17 and TNF-alpha, maintains the inflammatory loop. Untreated, it significantly reduces quality of life, increasing risks of depression and disabling joint destruction.

Epidemiology & Demographics

Prevalence is approximately 2-3% of the global population, with higher rates in Scandinavian and Northern European populations. Bimodal age of onset: first peak at 15-20 years and second peak at 55-60 years. Men and women are affected equally.

Etiological Mechanism

A complex interaction between polygenic predisposition (specifically the PSORS1 locus, HLA-Cw6 allele) and environmental triggers such as streptococcal pharyngitis, stress, local trauma (Koebner phenomenon), and certain medications (beta-blockers, lithium).

Primary Causes

Primary cause is an autoimmune dysregulation linked to genetic susceptibility. Secondary triggers include infections (Group A Streptococcus), medications (lithium, beta-blockers, antimalarials, NSAIDs), cold/dry weather, emotional stress, and alcohol consumption.

• Family History: Having one affected parent gives a 15% risk; both parents increases risk to 50%.
• Obesity: Increased adipose tissue produces pro-inflammatory adipokines, worsening severity and decreasing treatment efficacy.
• Smoking: Increases oxidative stress and is strongly linked to palmoplantar pustular variants and overall plaque severity.
• Medications: Use of lithium, beta-blockers, or abrupt withdrawal of systemic corticosteroids can trigger or exacerbate disease.

Stressed keratinocytes release LL-37 (cathelicidin), which complexes with self-DNA/RNA to activate plasmacytoid dendritic cells via Toll-like receptors (TLR7/9). These secrete IFN-alpha, activating myeloid dendritic cells, which migrate to lymph nodes and secrete IL-12 and IL-23. This drives the differentiation of Th1 and Th17 cells. Th17 cells migrate to the skin and release IL-17A, IL-17F, and IL-22, which stimulate keratinocyte hyperproliferation (acanthosis), incomplete maturation (parakeratosis), and production of chemokines (CXCL1, CXCL8) that recruit neutrophils to form Munro microabscesses.

Characteristic Clinical Presentation

• Pruritus: Moderate to severe itching over affected plaques, leading to excoriations.
• Skin Pain: Pain or burning sensation, especially if plaques fissure over joints.
• Joint Stiffness: Morning stiffness lasting >30 mins, indicative of concurrent psoriatic arthritis.

Physical Examination Signs

• Auspitz Sign
• Koebner Phenomenon
• Nail Pitting

• Psoriatic Arthritis (PsA): Inflammatory seronegative spondyloarthropathy developing in up to 30% of patients.
• Cardiovascular Disease: Increased risk of myocardial infarction, stroke, and atherosclerosis due to systemic inflammation.
• Metabolic Syndrome: Higher rates of obesity, insulin resistance, hypertension, and dyslipidemia.

Diagnostic Criteria & Guidelines

Diagnosis is primarily clinical based on typical plaque morphology, distribution, and signs (Auspitz, Koebner). Skin biopsy is rarely needed but shows regular epidermal hyperplasia (psoriasiform), parakeratosis, loss of granular layer, and Munro microabscesses. Severity is measured using the Psoriasis Area and Severity Index (PASI).

Differential Diagnosis

• Nummular Eczema
• Seborrheic Dermatitis
• Tinea Corporis
• Lichen Planus
• Pityriasis Rosea

Laboratory Tests & Biomarkers

• Uric Acid: Elevated in up to 50% of patients due to increased nucleic acid turnover from epidermal hyperproliferation.
• ESR/CRP: Elevated during acute flares or with concurrent psoriatic arthritis.
• HLA-B27: Positive in a subset of patients who develop axial psoriatic arthritis.

Imaging Modalities & Findings

• X-ray Hands/Feet: 'Pencil-in-cup' deformity at the distal interphalangeal (DIP) joints in cases of severe psoriatic arthritis.

• Mild
  Plaques localized to elbows, knees, or scalp. Generally managed with topical therapies.
• Moderate
  Widespread plaques affecting quality of life. Requires phototherapy or systemic oral agents.
• Severe
  Extensive body coverage or high impact areas (hands, feet, genitals). Requires biologic therapies.

Second-Line & Adjunctive Therapy

Narrowband UVB (NB-UVB) phototherapy 3 times weekly. Oral therapies include Methotrexate 7.5 to 15 mg PO once weekly (with daily folic acid 1 mg), or Apremilast 30 mg PO BID (titrated over 5 days).

Surgical & Procedural Management

None primarily indicated for psoriasis. Joint replacement may be necessary for severe end-stage psoriatic arthritis.

Recommended Lifestyle Changes

• Weight loss to reduce systemic inflammation and improve response to systemic therapies.
• Smoking cessation to reduce cardiovascular risk and disease flares.
• Daily use of thick emollients (petrolatum-based) immediately after bathing to maintain skin barrier.

Patient Counseling & Advice

Inform patients that psoriasis is a chronic, relapsing condition without a cure, but it is highly manageable. Emphasize that it is not contagious. Discuss the increased risk for cardiovascular disease and the importance of routine blood pressure and cholesterol screening.

Follow-Up & Monitoring Schedule

Routine PASI scoring every 3-6 months. For patients on Methotrexate, monitor CBC, LFTs, and creatinine every 1-3 months. Annual lipid panel and HbA1c screening for metabolic comorbidities.

Preventive Strategies

Avoid known triggers such as beta-blockers and NSAIDs where possible. Promptly treat streptococcal infections to prevent guttate flares. Maintain a healthy BMI.

Lifelong condition with fluctuating severity. Biologics can achieve PASI 90 or PASI 100 (complete clearance) in 60-80% of patients. Unmanaged severe disease reduces lifespan by 3-5 years due to cardiovascular events.