• Well-demarcated salmon pink plaques with silvery white scales (Fig. 152.1) over extensor surfaces, scalp, naval and natal cleft. They often tend to have a pink or red line in the intergluteal fold

• A white blanching ring, known as Woronoff’s ring, may be observed in the skin surrounding a psoriatic plaque.

Fig. 152.1 Psoriasis.

Proceed as follows:

• Look at the nails for pitting (Fig. 152.2) and onycholysis (separation of the nail plate from the bed; p. 675)

Fig. 152.2 Nail pitting.

Diagnosis

This patient has silvery white scales and nail pitting (lesion) caused by psoriasis (aetiology), with considerable itching (functional status).

Questions

Advanced-level questions

How is the severity of involvement usually estimated?

• The patient’s own perception of the disability

• Objective assessment of disability.

It is usually estimated by using the Psoriasis Area and Severity Index (PASI), which takes into consideration the area of involvement, thickness, redness and scaling. The maximal score on this index is 72, with mild, moderate and severe having scores of <10, 10–50 and >50, respectively.

What are the types of psoriasis?

Depending on the natural history

• Type 1: young patients with a strong family history, has a more aggressive disorder

• Type 2: older patients with no family history, has a more indolent course.

Depending on the nature of skin lesion

• Chronic plaque psoriasis

• With gradual peripheral extension, plaques may develop different configurations including:

• psoriasis gyrata, in which curved linear patterns predominate

• annular psoriasis, in which ring-like lesions develop secondary to central clearing

• psoriasis follicularis, in which minute scaly papules are present at the openings of pilosebaceous follicles.

• Rupioid and ostraceous, which relate to distinct morphological subtypes of plaque psoriasis:

• Rupioid plaques are small (2–5 cm in diameter) and highly hyperkeratotic, resembling limpet shells

• Ostraceous psoriasis are hyperkeratotic plaques with relatively concave centres, similar in shape to oyster shells.

• Inverse psoriasis: plaques evolve in the intertriginous areas and, therefore, lack the typical silver scale appearance because of moisture and maceration

• Guttate psoriasis: numerous small popular lesions with silvery scaling evolve suddenly over the body surface

• Pustular psoriasis: can be localized or generalized; superficial pustules may stud the plaques

• Erythrodermic psoriasis: generalized erythema and scaling; can be life threatening.

What do you know about the genetics of psoriasis?

• Clear identification of the causative gene has been difficult because of the extensive linkage disequilibrium (i.e. genes on one chromosome are inherited together and are not easily separable by recombination events) observed within the major histocompatibility complex (MHC).

• The major genetic determinant of psoriasis is PSORS1, which probably accounts for 35–50% of the heritability of the disease in multiple genomewide studies. PSORS1 is located within the MHC on chromosome 6p. Guttate psoriasis (an acute-onset form usually occurring in adolescents) is strongly associated with PSORS1,whereas late-onset cases of psoriasis vulgaris (usually in persons >50 years of age) and palmoplantar pustulosis are not associated with PSORS1.

• In a genomewide association study, polymorphisms in the genes for interleukin-12 (IL12B) and interleukin-23 (IL23R) are associated with psoriasis. These interleukins are cytokines that induce naive CD4 T cells to differentiate into type 1 helper T cells (Th1 cells) and type 17 helper T cells (Th17 cells), respectively; they have been identified as key mediators of psoriasis.

What do you know about the pathology of plaque psoriasis?

• Hyperproliferation of the epidermis

• Inflammation of the epidermis and dermis.

What do you understand by the term Koebner’s phenomenon?

Injury or irritation of psoriatic skin tends to provoke lesions of psoriasis in the site of trauma in some patients: this is known as the Koebner’s phenomenon.

Mention a few exacerbating factors?

• Drugs: beta-blockers, ACE inhibitors, lithium, indomethacin, antimalarials, alcohol

• Psychological factors

• Infection: β-haemolytic streptococci, HIV (pre-existing psoriasis may become more refractory to therapy and plaque psoriasis may change to the guttate form in HIV-positive patients)

• Injury to the skin: mechanical injury, sunburn.

How would you manage a patient with psoriasis?

• Educate the patient that there is no cure and that only suppression of the disease is possible

• Indications for treatment include symptoms (itching, pain, flexural intertrigo, limitation of manual dexterity), cosmetic problems or both

• Weight loss and smoking cessation may lower the risk or severity of psoriasis

• Initial treatment is topical when <20% of the body is involved

• Topical therapy in some form is usually the mainstay of treatment and includes:

• emollients (soft yellow paraffin or aqueous cream)

• keratolytic agents (salicylic acid)

• coal tar, which is usually used in combination with ultraviolet B phototherapy: Goeckerman treatment

• anthralin (often used according to the Ingram regimen: a daily coal tar bath, ultraviolet B phototherapy and 24 h application of an anthralin paste containing salicylic acid)

• topical steroids, such as betamethasone ointment

• calcipotriol (vitamin D), which is known to act locally to increase extracellular calcium concentrations, which leads to increased keratinocyte differentiation and decreased proliferation and scaling; it is an excellent alternative to steroids.

• Systemic therapy:

• Phototherapy (ultraviolet B radiation): narrowband ultraviolet B has replaced broadband ultraviolet B as it induces longer remissions and fewer burns (BMJ 2000;320:850–3).

• Photochemotherapy (methotrexate with ultraviolet a therapy)

• Methotrexate

• Etretinate and acitretin (vitamin A derivatives), retinoids

• Systemic steroids

• Ciclosporin, tacrolimus or mycophenolate mofetil.

• Novel approach:

• Anti-CD4 monoclonal antibody

• Biologic agents that block both interleukin-12 and interleukin-23, e.g. ustekinumab

• Agents that selectively block tumour necrosis factor-α, e.g. etanercept, adalimumab, infliximab.

What are the indications for systemic treatment?

• Failure of topical therapy

• Repeated hospital admissions for topical treatment

• Extensive plaque psoriasis in the elderly

• Generalized pustular or erythrodermic psoriasis

• Severe psoriatic arthropathy.

What underlying condition would you suspect when psoriasiform lesions are seen on the nose, ears, fingers and toes?

Such lesions are paraneoplastic eruptions associated with squamous cell carcinoma of the oropharynx, tracheobronchial tree and oesophagus: this is known as Bazex syndrome.

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