[23] Guttate psoriasis is an inflammatory condition characterized by numerous small, scaly, red or pink, droplet-like lesions (papules).

These numerous papules appear over large areas of the body, primarily the trunk, limbs, and scalp, but typically spare the palms and soles.

Guttate psoriasis is most commonly seen in children and young adults and diagnosis is typically made based on history and clinical exam findings.

[24] Skin biopsy can also be performed which typically shows a psoriasiform reaction pattern characterized by epidermal hyperplasia with elongation of the rete ridges.

[26] This form of psoriasis can be fatal as the extreme inflammation and exfoliation disrupt the body's ability to regulate temperature and perform barrier functions.

Genetics, seasonal changes, skin damage, climate, immunocompromised state, specific infections, and the use of some medications have been connected with different types of psoriasis.

[35][36] Around one-third of people with psoriasis report a family history of the disease, and researchers have identified genetic loci associated with the condition.

[medical citation needed] Psoriasis has been described as occurring after strep throat, and may be worsened by skin or gut colonization with Staphylococcus aureus, Malassezia spp., and Candida albicans.

[13][45] These immune cells move from the dermis to the epidermis and secrete inflammatory chemical signals (cytokines) such as interleukin-36γ, tumor necrosis factor-α, interleukin-1β, interleukin-6, and interleukin-22.

[18] Gene mutations of proteins involved in the skin's ability to function as a barrier have been identified as markers of susceptibility for the development of psoriasis.

[77] A genome-wide genetic study found that psoriasis and type 2 diabetes share four loci, namely, ACTR2, ERLIN1, TRMT112, and BECN1, which are connected via inflammatory NF-κB pathway.

[79] Topical corticosteroid preparations are the most effective agents when used continuously for eight weeks; retinoids and coal tar were found to be of limited benefit and may be no better than placebo.

Ointment and creams containing coal tar, dithranol, corticosteroids (i.e. desoximetasone), fluocinonide, vitamin D3 analogues (for example, calcipotriol), and retinoids are routinely used.

[86] Another topical therapy used to treat psoriasis is a form of balneotherapy, which involves daily baths in saltwater, such as the Dead Sea, combined with sun exposure.

A review of studies recommends that people who are susceptible to skin cancers exercise caution when using UV light therapy as a treatment.

The mechanism of action of PUVA is unknown but probably involves activation of psoralen by UVA light, which inhibits the abnormally rapid production of the cells in psoriatic skin.

Unlike generalized immunosuppressive medical therapies such as methotrexate, biologics target specific aspects of the immune system contributing to psoriasis.

One randomized control study suggested that 12 weeks of etanercept treatment reduced the extent of psoriasis in children with no lasting adverse effects.

[106] There is strong evidence to indicate that infliximab, bimekizumab, ixekizumab, and risankizumab are the most effective biologics for treating moderate to severe cases of psoriasis.

[citation needed] Another set of treatments for moderate to severe psoriasis are fumaric acid esters (FAE), which may be similar in effectiveness to methotrexate.

[109] Apremilast (Otezla, Celgene) is an oral small-molecule inhibitor of the enzyme phosphodiesterase 4, which plays an important role in chronic inflammation associated with psoriasis.

[110] It has been theorized that antistreptococcal medications may improve guttate and chronic plaque psoriasis; however, limited studies do not show that antibiotics are effective.

[44] Diet recommendations include consumption of cold water fish (preferably wild fish, not farmed) such as salmon, herring, and mackerel; extra virgin olive oil; legumes; vegetables; fruits; and whole grains; and avoid consumption of alcohol, red meat, and dairy products (due to their saturated fat).

[115] Many patients report improvements after consuming less tobacco, caffeine, sugar, nightshades (tomatoes, eggplant, peppers, paprika and white potatoes) and taking probiotics and oral Vitamin D.[116] There is a higher rate of celiac disease among people with psoriasis.

[80] Depending on the severity and location of outbreaks, people may experience significant physical discomfort and some disability, affecting the person's quality of life.

[53] Psychological distress can lead to significant depression and social isolation; a high rate of thoughts about suicide has been associated with psoriasis.

Mechanisms hypothesized to be involved in this relationship include the following: dysregulation of the renin–angiotensin system, elevated levels of endothelin 1 in the blood, and increased oxidative stress.

[7] The rate of psoriasis varies according to age, region and ethnicity; a combination of environmental and genetic factors is thought to be responsible for these differences.

[137] Admiral William Halsey missed out on the Battle of Midway because he contracted psoriasis while out at sea in the early months of American participation of World War II.

[141] Many novel medications being researched during the 2010s target the Th17/IL-23 axis,[141] particularly IL-23p19 inhibitors, as IL-23p19 is present in increased concentrations in psoriasis skin lesions while contributing less to protection against opportunistic infections.