Psoriasis is a chronic autoimmune condition that causes recurrent symptoms of psoriatic skin lesions. There is a large variation in how severely patients are affected with psoriasis. There appears to be a genetic component but no clear genetic inheritance has been established. Around a third of patients have a first degree relative with psoriasis. The symptoms start in childhood in a third of patients.
Patches of psoriasis are dry, flaky, scaly, faintly erythematous skin lesions that appear in raised and rough plaques, commonly over the extensor surfaces of the elbows and knees and on the scalp. These skin changes are caused by the rapid generation of new skin cells, resulting in an abnormal buildup and thickening of the skin in those areas.
Types of Psoriasis
Plaque psoriasis features the thickened erythematous plaques with silver scales, commonly seen on the extensor surfaces and scalp. The plaques are 1cm – 10cm in diameter. This is the most common form of psoriasis in adults.
Guttate psoriasis is the second most common form of psoriasis and commonly occurs in children. It presents with many small raised papules across the trunk and limbs. The papules are mildly erythematous and can be slightly scaly. Over time the papules in guttate psoriasis can turn into plaques. Guttate psoriasis is often triggered by a streptococcal throat infection, stress or medications. It often resolves spontaneously within 3 – 4 months.
Pustular psoriasis is a rare severe form of psoriasis where pustules form under areas of erythematous skin. The pus in these areas is not infectious. Patients can be systemically unwell. It should be treated as a medical emergency and patients with pustular psoriasis initially require admission to hospital.
Erythrodermic psoriasis is a rare severe form of psoriasis with extensive erythematous inflamed areas covering most of the surface area of the skin. The skin comes away in large patches (exfoliation) resulting in raw exposed areas. It should be treated as a medical emergency and patients require admission.
In children the distribution and presentation of psoriasis may differ from adults. Guttate psoriasis is more common in children, often triggered by a throat infection. Plaques of psoriasis are likely to be smaller, softer and less prominent.
There are a few specific signs suggestive of psoriasis:
- Auspitz sign refers to small points of bleeding when plaques are scraped off
- Koebner phenomenon refers to the development of psoriatic lesions to areas of skin affected by trauma
- Residual pigmentation of the skin after the lesions resolve
The diagnosis can be made based on the clinical appearance of the lesions.
Management depends on the severity of the condition. Psoriasis in children is usually managed and followed up by a specialist. It can be difficult to treat and psychosocial support is very important. The treatment options include:
- Topical steroids
- Topical vitamin D analogues (calcipotriol)
- Topical dithranol
- Topical calcineurin inhibitors (tacrolimus) are usually only used in adults
- Phototherapy with narrow band ultraviolet B light is particularly useful in extensive guttate psoriasis
Rarely, where topical treatments fail with severe and difficult to control psoriasis, children may be started on unlicensed systemic treatment under the guidance of an experienced specialist. This might include methotrexate, cyclosporine, retinoids or biologic medications.
There are two products that contain both a potent steroid and vitamin D analogue that are commonly prescribed and worth being aware of. These not licensed in children and will be guided by a specialist.
Nail psoriasis describes the nail changes that can occur in patients with psoriasis. These include nail pitting, thickening, discolouration, ridging and onycholysis (separation of the nail from the nail bed).
Psoriatic arthritis occurs in 10 – 20% of patients with psoriasis and usually occurs within 10 years of developing the skin changes. It typically affects people in middle age but can occur at any age.
Psychosocial implications of having chronic skin lesions, which may affect mood, self esteem and social acceptance and cause depression and anxiety.
Other co-morbidities that increase the risk of cardiovascular disease are associated with psoriasis, particularly obesity, hyperlipidaemia, hypertension and type 2 diabetes.
Last updated January 2020