DermatologyTier 1Disease (DEADMAN)

Cutaneous manifestations of systemic diseases - psoriasis

Description

Psoriasis is a systemic inflammatory disease with skin as the most visible organ, not a purely cutaneous condition
Skin severity (BSA/PASI) does not track systemic risk - even limited skin disease carries excess cardiometabolic and psychiatric morbidity
For full morphology/classification/topical-to-biologic ladder, see psoriasis - this note is the systemic-association and whole-patient lens

2-3% of Australians; risk of comorbidity rises with skin disease duration and severity
Severe psoriasis - life expectancy reduced by ~4-5 years, driven by cardiovascular disease
Psoriatic arthritis develops in ~20-30%, typically ~10 years after skin onset

Shared IL-23/Th17 axis inflammation drives disease at multiple organs simultaneously, not skin inflammation "spilling over"
- Systemic TNF-alpha, IL-17, IL-22 - implicated in accelerated atherosclerosis, insulin resistance
Chronic systemic inflammation -> endothelial dysfunction -> accelerated atherosclerosis independent of traditional risk factors
Shared genetic susceptibility loci with IBD and other IL-23-driven diseases explain overlap in disease clustering

Systemic screening to perform at every review, not only at diagnosis

Psoriatic arthritis - PEST questionnaire; ask about joint pain, stiffness, dactylitis, enthesitis, spinal symptoms at every visit (score >=3 -> rheumatology referral)
Cardiometabolic - BP, lipids, HbA1c/fasting glucose, weight/BMI annually
Mental health - screen for depression/anxiety (markedly increased prevalence, independent of disease severity)
Liver - consider NAFLD screening, particularly before/during methotrexate
Eyes - uveitis symptoms; cardiac - listen for aortic regurgitation murmur if axial disease present

Treat the comorbidity burden alongside the skin, not after it

Cardiovascular risk factor modification - smoking cessation, lipid management, BP control - treated as for any high cardiovascular-risk patient given the independent excess risk
Weight loss - improves both skin disease severity and biologic drug response/survival
Choose systemic therapy with comorbidity in mind:
- Concurrent psoriatic arthritis -> methotrexate or a biologic effective at both skin and joints
- Concurrent IBD -> anti-TNF or IL-23 inhibitor; avoid IL-17 inhibitors (can trigger/worsen IBD)
- Concurrent uveitis or axial disease -> TNF-alpha inhibitor preferred
- Concurrent NAFLD/at-risk liver -> avoid/caution with methotrexate
Never treat a flare with oral corticosteroids - risk of precipitating pustular/erythrodermic psoriasis on withdrawal, worsening the systemic picture acutely

Psoriatic arthritis - erosive, potentially irreversible if missed
Metabolic syndrome: obesity, T2DM, dyslipidaemia, hypertension
Accelerated cardiovascular disease (MI, stroke) - independent of traditional risk factors, risk tracks skin severity
NAFLD
Inflammatory bowel disease - shared pathogenesis
Depression, anxiety, increased suicidality
Uveitis, aortic regurgitation (with axial disease)
Lymphoma - small absolute risk increase

Comorbidity burden accumulates with disease duration - systemic screening should intensify, not relax, in longstanding disease
Effective systemic/biologic therapy may reduce (but does not eliminate) excess cardiovascular risk - an active area of evolving evidence
Unrecognised psoriatic arthritis is the single most consequential miss - joint erosion is irreversible, and skin clinics are often where the window to catch it exists

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