Psoriasis is classified by its different signs and symptoms as well as the location of the affected area.
Plaque Psoriasis
Plaque Psoriasis is the most common form of psoriasis with approximately 90% of psoriasis sufferers having this type. Plaque psoriasis usually affects the scalp, elbows, knees, lower back, hands, feet and genitals. The face is not usually involved.
The condition features circular to oval shaped patches of red skin which are raised, thickened and covered with silvery scales. The borders of each patch are well defined and small points of bleeding will occur if the scales are picked off. Each individual patch may come and go but it is more common for them to be present for years.
The typical appearance of plaque psoriasis is the basis for diagnosis however it may sometimes be confused with eczema or ringworm making a skin biopsy of the lesion necessary for confirmation of the diagnosis.
Guttate Psoriasis
Although the second most common form of psoriasis, Guttate psoriasis only affects 2% of all people with psoriasis. It is often the presenting form of psoriasis and most commonly affects children and young adults 2-3 weeks after a Streptococcal throat infection. The outbreak may go away and not return or it may go away and return with repeat episodes of Streptococcal infections.
Derived from the Latin word Gutta meaning droplet, the Guttate type of psoriasis appears as multiple, red, small (5-15mm), tear-drop shaped lesions usually on the trunk, arms, legs, face and scalp. The lesions are covered with a fine scale which is much finer than the scale found in plaque psoriasis.
This type of psoriasis often runs its course and goes away after a few weeks or months without treatment. However some cases, (especially in adults) will be more persistent and require treatment. The condition is usually diagnosed by its appearance however a throat culture or blood test may be required. Treatment with antibiotics is usually controversial.
Inverse Psoriasis
Well defined, smooth, bright-red patches appear in the folds of the skin especially the armpits, groin and under the breasts. Scaling is usually not present. The skin lesions may be triggered by a yeast overgrowth and once irritated and inflamed may be aggravated by sweat or the skin rubbing together.
Inverse psoriasis is usually treated with topical creams however treatments may irritate the area due to the sensitivity of the skin in the folds. Another issue is the risk of fungal infections due to the increased moisture in these irritated areas.
Pustular psoriasis
This uncommon form of psoriasis features clearly defined, raised bumps on the skin that are filled with non-infectious pus (pustules) which are not contagious. The skin under and around the pustules is reddened. They may appear on one localised part of the body or be wide spread over the whole body.
Attacks of Pustular Psoriasis are often triggered by medications, infections, stress or exposure to certain chemicals.
- Localised Pustular Psoriasis: In this form of psoriasis one or more patches of psoriasis spontaneously develop small pustules. The condition may be induced by aggressive over treatment or irritation.
- Palmoplantar Pustulosis: A chronic, persistent form of pustualr psoriasis that is localised to the palms of the hands and the soles of the feet. Typically affecting middle aged women this symmetrical form of psoriasis is difficult to treat.
- Acropustulosis: Localised to the fingers, thumbs and toes this rare form of pustular psoriasis features pustules that appear and then burst leaving bright red areas that may ooze, become scaly and/or crusty. The nails are often abnormal and crumbly and underlying lakes of pus may cause the nails to lift and “float away”. This form of psoriasis is often painful and results in permanent nail destruction.
- Generalised (von zumbusch) Pustular Psoriasis: This is a rare form of psoriasis that often signifies a worsening of the condition. The skin becomes red and sore with large patches of pin point pustules developing most often in skin folds and the groin. Symptoms often become systemic including a general feeling of unwellness, nausea, headache, joint pain, raised white blood cell count, fever, chills and occasionally death.
- Juvenile Pustular Psoriasis: This is the rarest of all pustular psoriasis and affects children.
Erythrodermic Psoriasis
This is the least common type of psoriasis and is potentially quite serious. Generally a very large portion, if not most of the skin is intensely red and swollen. The rash usually itches and burns and appears to be peeling. The increased blood flowing to the affected skin areas can cause a strain on the heart. Dehydration, infection and fever often affect people with this form of psoriasis and a combination of treatments is usually required.
The initial onset of Erythrodermic psoriasis is often triggered by severe sunburn, prolonged use of corticosteroids or other medications or a prolonged period of increased activity of poorly controlled psoriasis.
Psoriatic Arthritis
This condition often occurs in conjunction with the skin related psoriasis. The joints become painful, stiff and swollen with decreased movement, morning stiffness and general tiredness. The condition is not dissimilar to rheumatoid arthritis in presentation.
Nail Psoriasis
Nail involvement is common for people with psoriasis. If affected, the nails become pitted and may lift off the nail bed.
Seborrheic Psoriasis
The scalp is the most common area affected by psoriasis. It may cover a small area at the back of the head or upper neck or it may involve the whole scalp. This type of psoriasis may spread onto the forehead and into the ears however the face is rarely affected.
Seborrheic psoriasis features a well defined rash with very thick white scales that are often very firmly attached to the hair. Although hair loss is not generally caused by seborrheic psoriasis the hair is usually thinner in the affected areas.
Seborrheic psoriasis and seborrheic dermatitis (dandruff) are often confused and even with biopsy may be difficult to tell apart. Doctors may refer to the rash as “seborrhiasis” if they are unable to separate the two conditions.