Genetics & immune system involvement are the two key factors behind psoriasis, although the causes are not fully understood. It tends to run in families, although that is due to genetic factors rather than contagion. (Psoriasis is not contagious.)
Psoriasis is a condition thought to be related to the immune system, resulting from the body’s T-cells mistakenly attacking healthy skin cells, thereby causing an overproduction of cells at the deepest layers of the skin. The symptoms of the disease often recede & then flare up, & some correlation has been made between flare-ups of symptoms & certain triggers, including drinking alcohol, smoking cigarettes, external & emotional stress, hormone level shifts (such as at puberty & menopause), certain medications (lithium, anti-inflammatories such as ibuprofen, ACE inhibitors which treat high blood pressure, & some antimalarial medicines), & injuries to the skin. In the case of guttate psoriasis, symptoms develop following a streptococcus infection of the throat (strep throat).
Psoriasis is a skin condition causing the development of inflamed, flaky, crusty red patches of skin covered in silvery scales, which can be itchy & sore. These occur mostly on the elbows, knees, scalp, & low back. Psoriasis is a chronic (long-term) condition caused by hyperproduction of skin cells. For some patients symptoms are mild, for others they can be debilitating.
The severity of psoriasis symptoms varies significantly from case to case. Some cases will have localised symptoms (limited to the scalp or elbow joints for example), in others the affected skin can be all over the body & in larger areas. There is typically a pattern of worsening symptoms, which last for some weeks or months, followed by a period of improvement.
Different types of psoriasis have different symptoms.
Plaque psoriasis: patches of raised red or pink skin that are itchy & scaly, there may be smaller bumps as well, usually affecting the elbows, knees, & scalp. This psoriasis has a telltale sign called the Auspitz sign, where pulling off a dry flake of skin leaves a small spot of blood on the skin. It is the most common form of the disease.
Guttate psoriasis: small plaques or bumps of itchy, red, scaling skin that can affect large areas, & which appear suddenly following a sore throat.
Scalp psoriasis: symptoms include dry, flaking scalp & areas of red skin, & can be confused with dandruff & seborrheic dermatitis.
Nail psoriasis: affecting only the fingernails & toenails, where the nail is yellowish & separates from the nail bed (onycholysis), nails may be thickened, & may show small depressions in the surface; this condition is sometimes misdiagnosed as a fungal nail infection.
Inverse psoriasis: flat, red lesions in the folds & creases of the skin such as the armpits, genital area, groin, & glans (head of the penis), navel, & intergluteal folds (between the buttocks), which tend not to be scaly.
Pustular psoriasis: a rapid onset of small bumps, usually on the torso, which are filled with pus, & may be accompanied by a fever or other signs of systemic infection.
Erythrodermic psoriasis: this is a rare condition involving extensive areas of red skin which can cover the whole body, & may be accompanied by chills.
Psoriatic arthritis: skin symptoms of redness, itchiness, flaking & scaling, accompanied by swollen & painful joints and/or connective tissue.