What are the treatment guidelines for a patient diagnosed with psoriasis, considering disease severity, medical history, and potential comorbidities?

Psoriasis Diagnosis and Treatment Guidelines

Disease Severity Classification and Treatment Selection

For mild psoriasis (<5% body surface area), initiate treatment with high-potency topical corticosteroids combined with calcipotriene, which achieves 58-92% clearance rates. 1

Mild Psoriasis (Typically <5% BSA)

Topical therapy is the mainstay for mild disease:

• Apply clobetasol propionate 0.05% or betamethasone dipropionate 0.05% twice daily for a maximum of 2-4 weeks to thick plaques 1, 2
• Combine with calcipotriene (vitamin D analog) for synergistic effect and enhanced efficacy 1, 3
• Fixed-combination products (calcipotriene/betamethasone dipropionate) simplify regimens and improve compliance 3
• Maximum calcipotriene dose is 100g per week to avoid hypercalcemia 3

Critical safety monitoring for topical corticosteroids:

• Conduct clinical review every 4 weeks during active treatment 2
• No unsupervised repeat prescriptions for high-potency agents 4, 3
• Limit moderately potent preparations to maximum 100g per month 4, 3
• Alternate with periods of non-corticosteroid treatment each year 4
• Long-term use of potent topical corticosteroids causes skin atrophy, striae, and telangiectasia 3

Alternative topical agents when corticosteroids fail:

• Coal tar preparations (extremely safe, can use crude coal tar in petroleum jelly) 4
• Anthralin (dithranol) under carefully monitored conditions 4
• Tazarotene (retinoid) for localized plaques 3

Moderate-to-Severe Psoriasis (≥5% BSA or Vulnerable Areas)

Phototherapy is first-line treatment for moderate-to-severe disease:

• Narrowband UVB is a primary option for moderate-to-severe psoriasis 1, 3
• PUVA (psoralen plus UVA) is the least toxic systemic agent and first-line systemic treatment, with starting dose at 70% of minimum phototoxic dose read at 72 hours 4, 1
• Successive PUVA doses increased by 40% of immediately preceding dose if no erythema present 4
• 308-nm excimer laser allows selective targeting of localized resistant areas (scalp, skin folds) 1, 3

Indications for Systemic Therapy

Escalate to systemic therapy when:

• Failure of adequate trial of topical treatment 4, 2
• Body surface area involvement exceeds 5% 2
• Repeated hospital admissions for topical treatment 4
• Extensive chronic plaque psoriasis in elderly or infirm patients 4
• Generalized pustular or erythrodermic psoriasis 4, 2
• Severe psoriatic arthropathy 4, 2

Systemic Non-Biologic Therapies

Methotrexate

Methotrexate is especially useful in acute generalized pustular psoriasis, psoriatic erythroderma, psoriatic arthritis, and extensive chronic plaque psoriasis in elderly or infirm patients. 4

• Response time: 2 weeks 4, 1
• Initial dose must not exceed 0.2 mg/kg body weight 4
• Doses increased gradually from first dose 4
• Regular maintenance treatment may start one week after initial dose if laboratory results normal 4

Pretreatment assessment: History and examination, full blood count, liver function tests, serum creatinine 4

Absolute contraindications: Pregnancy, breastfeeding, wish to father children, significant hepatic damage, anemia, leucopenia, thrombocytopenia 4

Critical monitoring requirements:

• Contraception mandatory for men and women 4
• Conception must be avoided during treatment and for at least one menstrual cycle after stopping in women 4, 2
• Liver function tests performed weekly initially, then every 1-2 months when stable 4
• Main side effects are acute marrow suppression and long-term risk of hepatic fibrosis and cirrhosis 4

Drug interactions that increase methotrexate activity: Alcohol, salicylates, NSAIDs, co-trimoxazole, trimethoprim, probenecid, phenytoin, retinoids, pyrimethamine, furosemide 4

Cyclosporin

For moderate-to-severe psoriasis requiring rapid response, cyclosporin at 3-5 mg/kg/day provides the most rapid onset of action. 1

• Response time: 3 weeks 4, 1
• Duration of use: short 3-4 month "interventional" courses 1
• For erythrodermic psoriasis, cyclosporin 3-5 mg/kg/day provides rapid and impressive onset of action 1

Pretreatment assessment: History and examination, serum creatinine, blood pressure 4

Contraindications: Abnormal renal function, uncontrolled hypertension, previous or concomitant malignancy 4

Monitoring: Blood pressure and serum creatinine measured regularly; if renal function deteriorates, reduce dose or stop cyclosporin 4

Drug interactions to avoid: Aminoglycosides, amphotericin, trimethoprim, ketoconazole, phenytoin, rifampicin, isoniazid, NSAIDs 4

Retinoids (Acitretin/Etretinate)

Retinoids are very effective in acral or generalized pustular forms of psoriasis. 4

• Response time: 6 weeks 4
• Starting dose: 0.75 mg/kg body weight daily for 2-4 weeks, then titrate down to lowest effective dose 4

Pretreatment assessment: History and examination, full blood count, serum lipids, liver function tests 4

Absolute contraindication: Pregnancy or wish to conceive within two years of stopping treatment 4

Critical warning: Women must use adequate contraception for at least one month before treatment, during treatment, and for at least two years after stopping treatment with no exceptions 4

Other Systemic Agents

Hydroxyurea:

• Response time: 4 weeks 4
• Effective for severe psoriasis, safe when used up to one year 4
• Contraindications: Pregnancy, breastfeeding, severe anemia or leucopenia 4

Azathioprine:

• Response time: 4 weeks 4
• Response rate approximately 60% 4
• Main side effects: bone marrow toxicity, teratogenicity, oligospermia 4

Biologic Therapies for Severe Disease

TNF Inhibitors

For generalized pustular psoriasis, infliximab demonstrates rapid and often complete disease clearance as first-line biologic therapy. 1

• Infliximab dosing: 5 mg/kg infused at weeks 0,2, and 6, then every 8 weeks thereafter 1
• Adalimumab is effective for both skin and joint symptoms in psoriatic arthritis 1, 5
• Adalimumab dosing for psoriasis: 80 mg initial dose, followed by 40 mg every other week starting one week after initial dose 5
• Etanercept dosing for psoriasis: 50 mg twice weekly shows 46% PASI 75 response at 3 months 6

Critical warnings for TNF blockers:

• Increased risk of serious infections leading to hospitalization or death, including tuberculosis, bacterial sepsis, invasive fungal infections 5
• Perform test for latent TB; if positive, start TB treatment prior to starting biologic 5
• Monitor all patients for active TB during treatment, even if initial latent TB test negative 5
• Lymphoma and other malignancies reported, some fatal, particularly hepatosplenic T-cell lymphoma in adolescents and young adults with inflammatory bowel disease 5

IL-12/IL-23 Inhibitors

Ustekinumab targets the p40 subunit common to IL-12 and IL-23. 4

• Currently undergoing phase III clinical trials for psoriatic arthritis 4

Combination Strategies to Enhance Efficacy

Adding topical therapy to systemic agents accelerates clearance and improves outcomes:

• Ultrahigh-potency topical corticosteroid added to standard dose etanercept for 12 weeks 1
• Calcipotriene/betamethasone added to standard dose adalimumab for 16 weeks accelerates clearance 1
• Topical calcipotriene added to standard dose methotrexate improves outcomes 1

Special Considerations for Specific Psoriasis Types

Scalp Psoriasis

• Calcipotriene foam or calcipotriene plus betamethasone dipropionate gel for 4-12 weeks 3
• Excimer laser therapy for resistant cases 3

Facial and Intertriginous Psoriasis

• Low-potency corticosteroids to avoid skin atrophy 3
• Topical calcitriol is less irritating than other vitamin D analogs and better tolerated on sensitive skin 3

Palmoplantar Psoriasis

• May warrant systemic therapy even if BSA <5% due to quality-of-life impact 4

Psoriatic Arthritis

• Requires systemic therapy even if skin involvement <5% BSA 4
• Adalimumab, infliximab, and golimumab are FDA-approved for psoriatic arthritis 4, 5

Medications That Worsen Psoriasis (Avoid or Use Cautiously)

Systemic corticosteroids can cause severe, potentially fatal deterioration when discontinued and should be avoided. 4, 1, 3

Systemic corticosteroids should only be used for three rare conditions:

• Persistent uncontrollable erythroderma causing metabolic complications 4
• Generalized pustular psoriasis of von Zumbusch type if other drugs contraindicated 4
• Hyperacute psoriatic polyarthritis threatening severe irreversible joint damage 4

Other medications that may worsen psoriasis:

• Lithium, chloroquine, and mepacrine are associated with severe, potentially fatal psoriasis deterioration 4, 3
• Beta-blockers, NSAIDs, and alcohol may worsen psoriasis 4, 1, 3

Special Population Considerations

Pregnancy

• Narrowband UVB phototherapy is first-line for moderate-to-severe psoriasis in pregnant women, avoiding systemic agents 2
• Methotrexate is absolutely contraindicated during pregnancy and breastfeeding 2
• Retinoids carry high risk of fetal malformation if pregnancy occurs during treatment or within two years after completion 4

Elderly or Infirm Patients

• Methotrexate is especially useful for extensive chronic plaque psoriasis in elderly or infirm patients 4
• Dose should not exceed 0.2 mg/kg body weight in patients over 70 years 4

Common Pitfalls and Caveats

• Vitamin D analogs should be applied after phototherapy to avoid inactivation 3
• Patients receiving methotrexate and their family doctors must be given written instructions about dangerous drug interactions 4
• PUVA requires contraception, ultraviolet A eye protection, and shielding of genitalia unless specific need to treat 4
• Eye examination required before starting PUVA due to theoretical risk of cataract formation 4
• Rotational therapy (switching between treatment modalities every 1-2 years) may minimize cumulative toxicity 3