Psoriasis: What Is Happening in the Skin?

Psoriasis can be easy to file under “skin condition” and move on. The plaques are visible, so it is tempting to think the problem starts and ends at the surface. It does not.

Psoriasis is a chronic immune-mediated inflammatory condition. The plaque you can see is the visible result of abnormal immune signalling, accelerated growth and maturation of keratinocytes, and inflammation within the skin. For some people, the disease also affects the joints and is associated with wider physical and psychological health concerns.

For a nursing assessment, the visible skin changes are only part of the picture. A person may have a relatively small area of visible psoriasis but significant pain, scalp or genital involvement, nail disease, joint symptoms, treatment burden or distress. Understanding what is happening beneath the plaque helps you assess the patient rather than simply describe the rash.

Psoriasis is not contagious. It cannot be caught from touching someone, sharing equipment or providing personal care.

What is happening beneath the plaque?

In healthy skin, keratinocytes are produced in the deeper epidermis and gradually mature as they move towards the surface. This is normally a controlled process. In psoriasis, that control is disrupted.

There is no single cause. Genetic susceptibility and environmental influences interact with the immune system, and certain triggers can contribute to a flare in someone who is already predisposed. These can include infections, psychological stress, skin injury, some medicines, smoking and alcohol. A trigger is not the same thing as the underlying disease, and it is important not to frame a flare as something the patient has “caused”.

At immune level, psoriasis involves both innate and adaptive immune responses. Dendritic cells, T cells and inflammatory cytokines communicate with keratinocytes in a self-sustaining inflammatory loop. The interleukin-23 and interleukin-17 pathway is particularly important. You do not need to memorise every cytokine to follow the clinical picture. What is happening is a loop between immune signalling and keratinocyte activity.

Immune signalling tells keratinocytes to proliferate and behave abnormally, and the altered keratinocytes then help maintain the inflammatory response.

The epidermis becomes thickened because skin cells are being produced and moved towards the surface much more quickly than usual. They do not mature and shed in the normal orderly way, so cells accumulate at the surface and form scale. At the same time, inflammation and vascular changes within the skin contribute to the colour and tenderness of the plaque.

The result is often uncomfortable as well as visible. Plaques may itch, burn, feel sore or crack. Skin over joints, palms, soles or other high-friction areas can become painful with movement. Scratching and fissuring can lead to bleeding and further discomfort.

The visible plaque is therefore the end result of an active inflammatory process, not simply a build-up of “dry skin”.

What might you see?

Chronic plaque psoriasis is the pattern students are most likely to recognise. Plaques are usually well defined, raised and scaly. Common sites include the scalp, elbows, knees and trunk, but psoriasis can occur almost anywhere.

Appearance also varies with skin tone. On white skin, plaques may look pink or red with pale or silvery scale. On brown or black skin, redness may be less obvious and plaques may appear grey, violet, dark brown or otherwise different from textbook images. Darker marks may remain after active inflammation settles. NICE specifically warns that erythema can be underestimated in darker skin, so relying on redness alone can lead to under-recognition of severity.

Location matters as much as surface area. Psoriasis affecting the face, scalp, palms, soles, flexures or genitals may have a major effect on daily life even when the total area involved is small. Nail disease can cause pitting, thickening, discolouration or separation of the nail from the nail bed and may interfere with work, dexterity and self-care.

Other patterns can look different. Guttate psoriasis produces many smaller lesions and can occur after an infection such as streptococcal throat infection. Flexural psoriasis occurs in skin folds and may look smoother with less obvious scale because the area is moist. Pustular and erythrodermic forms are much less common but clinically important because they can be associated with systemic illness.

Psoriasis severity is not judged by how dramatic the skin looks at first glance. Site, symptoms, functional impact, psychological impact, joint symptoms and systemic features all contribute to the assessment.

If generalised pustular psoriasis or erythroderma is suspected, NICE recommends immediate same-day specialist assessment and treatment. A patient with widespread rapidly changing skin, generalised pustules, fever, tachycardia, malaise or other systemic deterioration needs prompt escalation through the appropriate local urgent or emergency pathway.

Psoriasis is more than skin

Joint symptoms deserve attention because psoriasis can also be associated with psoriatic arthritis. A patient may mention recurring joint pain, stiffness or swelling without realising it could be connected to their psoriasis. Morning stiffness, swollen joints and inflammatory back symptoms should not simply be dismissed as unrelated aches and pains.

NICE recommends an annual assessment for psoriatic arthritis for people with psoriasis, particularly during the first 10 years after psoriasis begins. In adults, a validated screening tool such as the Psoriasis Epidemiological Screening Tool (PEST) may be used, although PEST does not identify axial arthritis or inflammatory back pain. If psoriatic arthritis is suspected, NICE recommends referral to rheumatology.

For the student nurse, that does not mean diagnosing arthritis. It means recognising that joint symptoms are relevant, documenting what the patient reports and escalating concerns appropriately.

Psoriasis is also associated with comorbidities including cardiovascular disease and metabolic risk. NICE recommends cardiovascular risk assessment for adults with severe psoriasis at presentation and at least every 5 years thereafter, or more often if clinically indicated. In practice, this should be approached without blame. Smoking, alcohol use, weight, activity, blood pressure and other risk factors are sensitive areas, and support should be individualised rather than based on assumptions about the patient.

Mental wellbeing deserves the same attention. Visible plaques, shedding scale, itching, disrupted sleep, genital or scalp involvement and repeated treatment can affect confidence, relationships, clothing choices, work and social life. Some patients will have lived with comments, staring or the misconception that their skin is infectious. NICE advises assessing the physical, psychological and social impact of psoriasis and considering depression when assessing severity and when treatment is being escalated.

A patient may therefore say their psoriasis is “fine” while quietly changing how they dress, avoiding swimming, missing social events or struggling with a lengthy treatment routine. Asking what the condition is like to live with can reveal more than asking only whether the skin is better.

How treatment fits the mechanism

Once the pathophysiology is clear, the treatment options make more sense. The aim is not simply to remove scale. Treatment may reduce inflammation, slow abnormal keratinocyte activity, improve the skin barrier or target specific parts of the immune response.

Active topical treatment is first line for psoriasis, although NICE advises that phototherapy, conventional systemic treatment or targeted immunomodulatory treatment may be considered at the same time when topical treatment alone is unlikely to provide adequate control. Emollients can also help reduce dryness and scale. Topical corticosteroids reduce inflammation, while vitamin D preparations influence abnormal epidermal cell growth and differentiation. The exact preparation, potency, duration and site of application matter, so students should follow the prescription, current guidance and local medicines policy rather than assuming all creams are interchangeable.

When topical treatment is not enough, options can include phototherapy, conventional systemic medicines and targeted immunomodulatory treatments. Drugs such as methotrexate, ciclosporin or acitretin may be used in selected patients, while biologic and other targeted therapies act on specific inflammatory pathways. The fact that these treatments target tumour necrosis factor, interleukin-17 or interleukin-23 reflects the immune biology driving the plaques beneath the surface.

Systemic treatment also brings nursing considerations. Depending on the medicine, patients may need blood monitoring, infection screening, surveillance for adverse effects and specialist follow-up. During medicines reconciliation or assessment, know what the patient is prescribed and ask about relevant problems such as infection symptoms or missed monitoring. Do not independently stop or withhold an immunomodulatory medicine because a patient is unwell unless this is within an authorised plan or you have been directed to do so. Escalate to the registered professional or prescriber and follow local policy.

Treatment burden is easy to underestimate. Applying topical medication to large areas every day can be time consuming, messy and difficult to fit around work, study, childcare or fatigue. If a patient is not using treatment as prescribed, ask what is making the treatment difficult to use rather than labelling them as “non-compliant”.

The focus then moves from blame to the practical barriers the person is managing. Psoriasis is a long-term condition with periods of improvement and flare. A realistic treatment plan has to work in the patient's actual life.

Bring it back to the patient

Imagine you are caring for a patient admitted for an unrelated reason and you notice plaques over their elbows and scalp during assessment. They tell you they have had psoriasis for years and that it is “just my skin”. You could document the plaques and move on. A better assessment goes slightly further.

You might ask whether the plaques are painful or itchy, whether any difficult sites or nails are affected, what treatment they currently use and whether it is working for them. You can ask whether they have recurring joint pain, swelling or morning stiffness. You can notice whether the patient seems embarrassed about scale on the bed linen or clothing and make sure care is respectful rather than drawing unnecessary attention to it.

If the patient mentions persistent swollen joints or inflammatory stiffness, that is worth escalating because of the link with psoriatic arthritis. If they are receiving systemic or targeted treatment, check that it is captured accurately during medicines reconciliation and be alert to the monitoring and infection considerations relevant to that medicine. If their skin has suddenly become widespread, pustular or associated with fever and systemic illness, treat that as a change in clinical condition rather than assuming it is a routine psoriasis flare.

The student nurse is not there to diagnose the subtype or redesign the treatment plan. Your role is to notice, assess, listen, document and escalate. Understanding the pathophysiology helps you recognise which details need a closer look or escalation.

The plaque is visible, but the disease is inflammatory. Look at the skin, ask about the joints, consider the wider health picture and listen to how the condition is affecting the person.

References

British Association of Dermatologists (2023) Psoriasis – an overview. London: British Association of Dermatologists.

National Health Service (NHS) (n.d.) Psoriasis. NHS.

National Institute for Health and Care Excellence (NICE) (2012, updated 2017) Psoriasis: assessment and management. Clinical guideline CG153. London: NICE.

Nong, Y., Han, G. and Hawkes, J.E. (2024) ‘Expanding the Psoriasis Framework: Immunopathogenesis and Treatment Updates’, Cutis, 113(2), pp. 82–91. doi:10.12788/cutis.0949.