Psoriasis Diagnosis and Management

Clinical Diagnostic Features

The American Academy of Dermatology recommends diagnosing psoriasis clinically based on the presence of characteristic erythematous, scaly plaques with silvery scale, typically on extensor surfaces, without requiring laboratory investigations in most cases 1, 2
Plaque characteristics, such as well-demarcated, raised erythematous plaques covered with silvery-white scale, distinguish psoriasis from other conditions 1, 2
Nail involvement, including pitting, onycholysis, oil spots, and subungual hyperkeratosis, supports the diagnosis of psoriasis, particularly when associated with distal interphalangeal joint disease 3

The American Academy of Dermatology recommends assessing patient-reported disability and objective body surface area (BSA) at every visit, with BSA ≥10% generally defining moderate-to-severe disease requiring systemic therapy 1, 2, 4
The Psoriasis Area and Severity Index (PASI) score, ranging from 0-72, is used primarily in clinical trials, with PASI ≥10 indicating moderate-to-severe disease 4
All patients with cutaneous psoriasis should be informed about the association with psoriatic arthritis and screened for musculoskeletal symptoms, including morning joint stiffness, joint swelling, and enthesitis 5, 6, 3

The American Academy of Dermatology recommends evaluating patients with psoriasis for associated conditions, including cardiovascular risk factors, mental health, and inflammatory bowel disease 5, 3
Referral to dermatology is indicated for uncertain diagnosis, moderate-to-severe disease, failure of topical therapy, or need for systemic agents or phototherapy 1, 2
Referral to rheumatology is indicated for any suspicion of psoriatic arthritis based on joint symptoms 5, 3

Failing to screen for joint symptoms can lead to irreversible joint damage, with 15-30% of psoriasis patients developing psoriatic arthritis 5, 3
Medications such as beta-blockers, NSAIDs, lithium, and antimalarials can precipitate or severely worsen psoriasis 1, 2, 7

The British Medical Journal recommends documenting all medications for drug interaction assessment, especially if systemic therapy is considered, in patients with psoriasis 8
According to the British Medical Journal, baseline laboratory testing for all systemic agents should include complete blood count, liver function tests, serum creatinine and BUN, and electrolytes 9, 10, 8, 11, 12, 13
The British Medical Journal suggests that additional agent-specific testing, such as eye examination for cataracts for PUVA, pregnancy test in women of childbearing age for methotrexate, and serum lipids and pregnancy test for etretinate, should be performed before initiating systemic therapy 9, 8
The British Medical Journal recommends liver examination and clinical assessment for hepatomegaly before methotrexate, and measuring blood pressure on at least two occasions before initiating cyclosporine or methotrexate 8
The British Medical Journal advises documenting contraception for all women of childbearing age before systemic therapy, particularly for methotrexate, etretinate, or cyclosporine 9, 8