History
A 25-year-old man presents with a rash on his knees. This had gradually worsened over three years. In addition he had previously had dandruff and more recently noticed his nails changing, for which his GP treated him for a fungal nail infection, but with no improvement. He is a smoker and drinks 35 units of alcohol per week. He has noticed an improvement during the summer months and has also developed pains in his elbow and knees. His sister had a similar rash over her elbows.
Examination
There are erythematous plaques on his knees with clearly defined borders and overly-ing thick scale (Fig. 12.1). There is fine scale throughout the scalp and in his external auditory canals. Examination of his finger nails reveal three nail plates with pitting and onycholysis.
Questions
• What is the diagnosis?
• What are the risk factors for the disease?
• Are his joint pains relevant?
Medicine
Clinically this patient has chronic plaque psoriasis. This is a chronic inflammatory disease that affects 2 per cent of the population. It affects not only the skin, but can also affect the nails and joints. Psoriasis can present in several different ways, but chronic plaque psoriasis is characterized by well demarcated erythematous plaques which have an over-lying silvery scale that frequently affects the extensor aspects of the elbows and knees, as in this patient. Differential diagnoses of chronic plaque psoriasis include discoid eczema, tinea corporis, lichen simplex and mycosis fungoides (T-cell lymphoma). Risk factors for psoriasis include a positive fam-ily history. In addition, possible triggering and exacerbating factors include stress, smoking, alcohol, streptococcal infection and medications such as -blockers and non-steroidal anti-inflammatory drugs (NSAIDs). Physical trauma can be a major factor in triggering lesions, the so-called Koebner phenomenon. Nail disease in psoriasis is common, affect-ing the fingernails and toenails. Nail changes (Fig. 12.2) include pitting and onycholysis (sep-aration of the nail plate from the nail bed), and subungal hyperkeratosis. Oil spots are pathog-nomic and appear as yellow-brown spots under the nail plate. Basic histopathology shows there is marked thickening of the epidermis (plaques) and dilated blood vessels just beneath the epi-dermis (erythema), and neutrophils infiltrate up into the stratum corneum where they form microabscesses of Munro (inflammation). The different clinical presentations of psoriasis include guttate, pustular, erythrodermic and palmoplantar. It is thought that 5–10 per cent of patients with psoriasis have joint involvement known as psoriatic arthritis, which may precede, present with, or most com-monly follow, the skin involvement. There are five different clinical types: asymmetric (mono– or oligoarthropathy), symmetrical polyarthritis (rheumatoid arthritis-like), distal interphalangeal joint disease, arthritis mutilans, and ankylosing-spondylitis–like. Chronic plaque psoriasis can be treated with topical therapy including emollients, steroid ointments, vitamin-D analogues, coal tar-based preparations, dithranol, salicylic acid and phototherapy. Joint disease may respond to NSAIDs, methotrexate or ciclosporin. Systemic drugs are reserved for moderate-to-severe recalcitrant disease and include ciclosporin, methotrexate, acitretin and in more recent years the biologics that include the biologics such as infliximab, which has anti-tumour necrosis factor activity.
KEY POINTS
• Psoriasis is a chronic inflammatory disease affecting 2 per cent of the population.
• It affects not only the skin but can also affect the nails and joints.
• There are multiple modalities of treatments including topical, phototherapeutic and systemic drug preparations.
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