2nd July 2023

Psoriasis

There are various types of psoriasis. Psoriasis is a group of chronic inflammatory skin conditions characterised by clearly defined, red and scaly plaques. It is thought to be a multifactorial disorder that is an immune-mediated inflammatory disease. Plaque psoriasis is the most common type of psoriasis across all ethnic groups and populations.

The main types of psoriasis are summarised below:

Type	Key Features	Image
Chronic plaque psoriasis	Persistent Plaques >3cm in size Primarily affects extensor surfaces – elbows, knees, and lower back Can range from mild isolated plaques to extensive plaques	Image Source: Wikimedia Commons (2019). Psoriasis on elbow, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Psoriasis_on_elbow.jpg (Accessed on: 14 March 2023).
Guttate psoriasis	Acute psoriasis triggered by streptococcal throat infection Widespread small plaques “Teardrop appearance” Resolves after several months Treatment: UVB therapy	Image Source: Wikimedia Commons (2010). Guttate psoriasis, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Guttate_psoriasis.jpg (Accessed on: 14 March 2023).
Flexural psoriasis	Affects flexural surfaces instead of extensor surfaces Smoother and well-defined patches compared to plaque psoriasis Often becomes colonised by candida Treatment: topical steroids	Image Source: Wikimedia Commons (2013). Schuppenflechte am Knie, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Schuppenflechte_am_Knie.JPG (Accessed on: 14 March 2023).
Scalp psoriasis	Often the first site of psoriasis Hyperkeratotic lesions	Image Source: Wikimedia Commons (2021). Stelara before and after pictures-1, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Stelara_before_and_after_pictures-1.png (Accessed on: 14 March 2023).
Nail psoriasis	Changes include pitting, onycholysis, yellowing and visible ridges Classically associated with the development of inflammatory psoriatic arthritis	Image Source: Wikimedia Commons (2009). Psonail, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Psonail.jpg (Accessed on: 14 March 2023)
Erythrodermic psoriasis	Dermatological emergency Rare complication of chronic plaque psoriasis Usually preceded by another form of psoriasis but can be presenting complaint Systemic illness – temperature dysregulation, electrolyte imbalance and can cause organ dysfunction and cardiac failure	Image Source: Wikimedia Commons (2017). Red (burning) Skin Syndrome – Feet Collage, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Red_(burning)_Skin_Syndrome_-_Feet_Collage.jpg (Accessed on: 14 March 2023)

Types of psoriasis and common features

Psoriasis is primarily a clinical diagnosis; however, diagnosis can be supported through skin biopsy. Additionally, it can present as psoriatic arthritis without skin involvement in up to 15% of cases. The main features of psoriatic arthritis include inflammation at the distal interphalangeal joints as well as nail changes. It can also affect other joints and vary in its presentation of either symmetrical or asymmetrical oligo/polyarthritis. Severity of psoriasis can be assessed through history, examination, and assessment tools, such as the Psoriasis Area and Severity Index (PASI) scoring tool.

Treatment depends on severity. Mild disease can be managed with topical agents such as emollients, coal tar preparations, salicylic acid, vitamin D analogues (calcipotriol), topical steroids or combination ointments/gels. Treatment can be escalated to phototherapy, systemic therapy with immunomodulatory medications such as DMARDs or in more severe cases biologics or targeted therapies such as anti-TNFa treatments. These are reserved for severe psoriasis that is resistant to conventional treatments.

Certain medications are known to exacerbate psoriasis. These include beta blockers, lithium, antimalarials, NSAIDs, ACE inhibitors and infliximab.

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