Contributors:Patricia Nguyen, MScBMC, Alaina Mueller, Jerry Ferro, Antonella Melani, MD, Ashley Mauldin MSN, APRN, FNP-BC
Psoriasis is a chronic autoimmune disease that primarily causes skin inflammation, and is typically characterized by well circumscribed erythematous patches topped with white silvery scales.
Now, let’s go over some physiology. Normally, the skin is divided into three layers, the epidermis, dermis, and hypodermis. The hypodermis is made of fat and connective tissue that anchors the skin to the underlying muscle. Just above the hypodermis is the dermis, which contains hair follicles, nerve endings, glands, blood vessels, and lymphatics. And just above the dermis is the epidermis, which itself has multiple cell layers that are composed of developing cells called keratinocytes.
Keratinocytes start their life at the lowest layer of the epidermis, called the stratum basale, or basal layer, which continually divide and produce new keratinocytes. As keratinocytes in the stratum basale begin to mature, they migrate into the next layers, called the:stratum spinosum, stratum granulosum, stratum lucidum, and finally, the stratum corneum, which is the uppermost and thickest epidermal layer.
As new keratinocytes push up into the stratum corneum, older dead cells are sloughed off forming skin flakes or dandruff. In this way, the thickness of the epithelium remains constant, with a regulated turn-over of keratinocytes.
Now, there isn’t a single cause of psoriasis, but rather it’s a multifactorial disease, with a combination of genetic predisposition and environmental risk factors and triggers; these include stress, traumatic insults, infection, and obesity, smoking, alcohol use, and taking certain medications like antimalarials or lithium.
Regardless of what triggers the disease, there’s an abnormal inflammatory process that causes dilation of the blood vessels at the border between the dermis and epidermis. This attracts immune cells, which infiltrate into the epidermis, causing chronic damage to the skin.
As a result, keratinocytes begin to proliferate excessively and mature abnormally. Over time, as keratinocyte proliferation outpaces sloughing off, these cells begin to pile up.
This hyperproliferation thickens the epidermal layers, particularly the stratum corneum and stratum spinosum; but thins out the stratum basale. In addition, the immature keratinocytes don’t adhere to each other properly, causing breaks in the epidermis. This weakens the skin and results in the formation of a psoriatic plaque, with the characteristic scaling and erythema.
Typically, clients with psoriasis have periods of exacerbations called flares, and periods of remission during which there are few or no symptoms. Now, according to its cutaneous manifestations, psoriasis can be classified into five main subtypes, including chronic plaque psoriasis, guttate psoriasis, inverse psoriasis, pustular psoriasis, and erythrodermic psoriasis.
Chronic plaque psoriasis is the most common type of psoriasis. Clients typically present with well circumscribed, raised, erythematous patches from the underlying dilated blood vessels, and these patches are topped with white silvery scales. In clients with skin of color, the additional melanin can make the lesions appear purple or brown with grayish scales.Psoriasis lesions might be itchy or painful, and if the scales are picked off, the underlying blood vessels can get injured, causing localized spots of bleeding, called an Auspitz sign. Chronic plaque psoriasis usually involves the scalp, elbows, and knees, as well as the lower back and groin.
On the other hand, guttate psoriasis typically appears as small, red, dark purplish or hypopigmented, individual spots on the trunk and limbs, and is often triggered by a streptococcal infection.
Next, inverse psoriasis appears as smooth and shiny red or purplish lesions that lack scales; these typically form within skin folds, such as in the under arms, behind the knees, or the groin area.
Pustular psoriasis appears as areas of red or purplish skin with small, white pustules, which are filled with pus formed from dead immune cells; these lesions are usually tender and form on the hands and feet.
Finally, erythrodermic psoriasis is usually the most severe subset, and appears as fire-red or dark purplish scales that can cover a large body surface area; these lesions are often extremely itchy and painful, and the skin may fall off in large sheets.
Now, in addition to these cutaneous manifestations, clients with psoriasis may present with additional findings, such as nail abnormalities like pitting and discoloration; as well as dactylitis, or severe inflammation of the fingers and toes; and some may develop psoriatic arthritis.
Now, the diagnosis of psoriasis primarily involves the client’s history and physical assessment. There are no specific laboratory tests for psoriasis, but in certain cases, a skin biopsy can be done to confirm the diagnosis.
Although there’s no cure for psoriasis, certain treatment options can be used to help mitigate some of the symptoms and improve the client’s quality of life. Treatment is chosen based on the severity of the disease, as well as the efficacy and response to treatment, and affordability.