What are the different types of psoriasis?
Psoriasis may appear at any age, but there are two peak onset periods; during childhood/early adulthood (early onset psoriasis) and after age 40 (late onset) (1). There is strong evidence for a genetic predisposition to psoriasis, in particular to childhood psoriasis. It is estimated that 71% of patients with childhood psoriasis have a positive family history (2).
There are multiple forms of psoriasis and they are often distinguished based on the location and appearance of the lesions. The presence and distribution of psoriatic plaques is highly variable; some people suffer from a single plaque of psoriasis on a specific part of their body, whereas others suffer from psoriasis all over their bodies.
Psoriasis is accompanied by itching in 60% to 70% of cases (3).
There is to date no permanent cure for psoriasis and eruptions often recur. However, most treatments are related to significant improvements in quality of life.
Classification according to type of lesion?
Some dermatologists believe that the term "psoriasis" in fact covers six or seven different conditions, which in the future may be distinguished from each other and treated separately. The effect of the drugs that are available today (e.g. local and systemic treatments) is to clear the psoriatic plaques and to prevent relapse.
Psoriasis is classified according to the type of lesion into the following subgroups
Plaque psoriasis (psoriasis vulgaris)
Psoriasis vulgaris is the clinical term for plague psoriasis. Vulgaris means “common” and psoriasis vulgaris is the most prevalent form of psoriasis affecting 95% of people with psoriasis. Lesions are clearly demarcated and may be surrounded by a clear ring. The condition can appear on various parts of the body and lesions vary depending on the body part affected.
Plaques vary in size and number and they can be both thin and thick, Scratching results in the appearance of fine droplets of blood. The colour pf the plaques may vary in intensity, being redder towards the edge of a plaque than at the centre.
The plaques are often found symmetrically on the outer arms and legs, especially on both elbows and/or both knees, but any part of the body can be affected.
The plaques sometimes appear in certain shapes, and they are always clearly demarcated (it is easy to see where it starts and ends). It is sometime refered to as psoriasis circinata (from the Latin circum) where lesions are ring shaped.
Small, round, scattered lesions are typical of guttate psoriasis or psoriasis guttata. Instead of extensive, thick plaques, this type of psoriasis presents with small red scaly dots which look like drops of water sprinkled over the body. Guttate psoriasis is more prevalent in children and young adults than older adults and disease onset is strongly related to streptococcal throat infection (such as rhinopharyngitis, pharyngitis or tonsillitis) (4). This type of psoriasis tends to go into spontaneous remission after several weeks and can reappear either in the same form, or as classical plaque psoriasis.
Nummular psoriasis is characterised by rounded plaques which are several centimetres in diameter. Their shape and size are more or less the same as a coin.
This type of psoriasis affects less than 10% of patients. It can appear as a complication to plaque psoriasis, as a result of taking certain medicines, or of abruptly withdrawing from them. Lesions are characterized by pustules. The palms of the hands, soles of the feet, fingers and nails are most affected.
Erythrodermic psoriasis can affect most of the body's surface, and skin becomes erythemato-squamous (covered by red, scaling patches). Limited patches of pustules may appear.
Psoriatic arthritis is characterised by inflammation affecting joints and in some cases entheses (=the point at which a tendon inserts into the bone). It is estimated that approximately 1% of the world population is affected by psoriatic arthritis (5).
Most severe forms of psoriasis
Some forms of psoriasis are more severe and particularly resistant to treatment. These are pustular psoriasis, erythrodermic psoriasis and psoriatic arthritis. These should receive very careful medical treatment, in collaboration with dermatologists.
We talk about psoriasis universalis when lesions are present over the entire skin. This form of psoriasis is quite rare.
(1) Youn et al., J Dermatol, 1999; Henseler et al., J Am Acad Dermatol, 1985.
(2) Morris et al., Pediatr Dermatol, 2001.
(3) Sampogna, Br J Dermatol, 2004,; Wolkenstein, JEADV, 2006.
(4) Mallbris et al., J Invest Dermatol, 2005.
(5) Gladman et al., Ann Rheum Dis, 2005.