Chronic plaque, guttate and flexural psoriasis

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Psoriasis is a relapsing inflammatory disorder with several morphologies. Diagnosis is usually clinical, but accuracy depends on examining the entire skin, scalp, nails and joints rather than naming one isolated scaly patch.

Extent alone is an incomplete severity measure. Genital, facial, scalp, palmoplantar and nail disease may be functionally or psychologically severe despite low body surface area, and colour-based scoring can miss inflammation in darker skin.

The practical sequence is to confirm phenotype, screen for instability and arthritis, measure impact, select a tolerable site-specific topical plan, teach quantities and review points, then escalate when goals are not met.

Key points

Chronic plaque psoriasis produces persistent, well-demarcated scaly plaques, classically on extensor elbows and knees, scalp, sacrum and umbilicus; colour may be red, violaceous, brown or grey according to skin tone.
Guttate psoriasis is an acute shower of small scaly papules, often one to three weeks after streptococcal pharyngitis; inspect the throat but do not promise that antibiotics will clear the eruption.
Flexural psoriasis is smooth, sharply bordered and minimally scaly in axillae, groin, inframammary folds or natal cleft; exclude candidiasis, dermatophyte infection and contact irritation when atypical.
Record patient and clinician global severity, body surface area, difficult sites, nail disease, systemic upset, life impact and joint symptoms; erythema can be underestimated in deeply pigmented skin.
Topical treatment is first-line for most limited disease, but formulation and potency must follow site: thick trunk plaques tolerate different therapy from face, flexures and genitals.
Refer for diagnostic uncertainty, more than 10% body surface area, inadequate topical control, major functional or psychosocial impact, phototherapy need, significant nails, or any childhood psoriasis.
Generalised pustular psoriasis or erythroderma requires immediate same-day specialist assessment, while suspected psoriatic arthritis requires rheumatology referral as soon as it is recognised.
Ask about smoking, alcohol, weight, cardiovascular risk, mood and treatment practicality without implying blame; agree goals that matter to the person.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Immune and genetic susceptibility

Psoriasis is a chronic immune-mediated disorder with polygenic susceptibility. Family history increases probability, but its absence does not exclude disease and psoriasis is neither infectious nor caused by poor hygiene.

Phenotype-specific triggers

Guttate psoriasis often follows a streptococcal throat infection, particularly in children and young adults. Trauma can provoke plaques through the Koebner response, while stress, smoking, alcohol and some medicines may modify activity.

Medicine associations

Lithium, beta blockers, antimalarials and some immune therapies can aggravate psoriasis in susceptible people. Establish timing and indication before changing treatment; abrupt withdrawal of systemic corticosteroids can destabilise disease.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Accelerated epidermal turnover
T-cell and cytokine signalling drives keratinocyte proliferation and impaired maturation. The resulting thickened epidermis and retained nuclei produce sharply demarcated plaques with adherent scale.
2
Inflammation across compartments
Psoriatic inflammation can involve skin, nails, entheses, peripheral joints and the axial skeleton. Visible surface area therefore understates disease burden when high-impact sites or joints are affected.
3
Flexural surface difference
Moist opposing surfaces reduce visible scale, so flexural psoriasis appears smooth and glazed rather than classically silvery. Friction and maceration can add soreness or fissuring without changing the underlying psoriatic process.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Chronic plaque pattern

Symmetrical, sharply marginated plaques with dry adherent scale affect extensor limbs, scalp margin, sacrum or umbilicus. Removing scale may reveal pinpoint bleeding, but deliberate scraping is unnecessary and can traumatise skin.

Guttate eruption

Numerous small oval or droplet-like scaly lesions arise abruptly across trunk and proximal limbs, commonly after sore throat. Ask about infection, medicines and sexual risk because other widespread papulosquamous eruptions can mimic it.

Flexural phenotype

Smooth shiny plaques occupy skin folds with little scale; fissuring may be painful. Symmetry and psoriasis elsewhere help, whereas satellite pustules, an advancing border or dominant exposure suggest another diagnosis.

Inflammation in darker skin

Activity may look violaceous, deep brown or grey rather than bright red. Palpate thickness, warmth and scale, compare with nearby skin, and ask about itch and tenderness; pigment alteration may persist after activity settles.

Joint warning symptomsRed flag

Morning stiffness, swollen joints, whole-digit swelling, heel pain or inflammatory back pain can precede or follow cutaneous disease. A negative PEST does not exclude axial arthritis or inflammatory back pain.

Systemic instabilityRed flag

Fever, malaise, widespread pustulation, rapidly spreading erythema, oedema, shivering or reduced urine output are not routine plaque symptoms. Check observations and arrange same-day specialist assessment.

Red flags requiring action

Diffuse tender erythema, sterile-looking pustules, fever, malaise, shivering, oedema, dehydration or altered observations require same-day specialist care.
A hot swollen joint, dactylitis, inflammatory back pain or painful enthesitis suggests psoriatic arthritis and needs prompt rheumatology assessment.
Rapid change after starting or stopping a medicine, especially systemic corticosteroid withdrawal, requires a full medication timeline and urgent advice if disease is unstable.
Major mood disturbance, hopelessness or self-harm thoughts are clinical severity markers and require direct risk assessment and appropriate urgent mental-health support.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First assessment: morphology and full skin examinationFirst step
Why
Establish plaque, guttate or flexural phenotype and detect scalp, nail, palmoplantar or genital involvement.
Interpretation and limitations
Typical symmetric plaques and supporting sites usually establish the diagnosis. An isolated, unilateral, ulcerated or treatment-resistant lesion should reopen the differential rather than attract stronger empirical steroid.
02
Severity and impact record
Why
Document static clinician and patient global assessment, body surface area, difficult sites and functional or psychosocial impact.
Interpretation and limitations
More than 10% body surface area is one NICE example of extensive disease, but severe nail, genital, facial, hand or foot disease can merit escalation at much lower extent.
03
Annual psoriatic arthritis screen
Why
Identify peripheral joint, entheseal and axial symptoms before irreversible damage develops.
Interpretation and limitations
Use a validated adult tool such as PEST, then ask separately about inflammatory back pain because PEST does not detect axial disease; suspected arthritis warrants rheumatology referral.
04
Targeted mycology
Why
Distinguish dermatophyte infection from asymmetric annular, flexural or steroid-modified disease.
Interpretation and limitations
Microscopy can give earlier support and culture identifies fungus more slowly; a negative specimen is less reassuring if too little scale or the wrong edge was sampled.
05
Skin biopsy for genuine uncertainty
Why
Exclude an inflammatory, infectious or neoplastic mimic when history and examination remain discordant.
Interpretation and limitations
Histology can support psoriasis but must be matched to site and treatment history. Sample an active representative lesion with consent and tell pathology the competing diagnoses.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Seborrhoeic dermatitis

Greasy scale on scalp, eyebrows, nasolabial folds and ears is less sharply bordered than plaque psoriasis. Overlap exists, so examine extensor sites, umbilicus and nails before forcing a binary label.

Dermatophyte infection

Tinea corporis or cruris often has an active advancing edge, relative central clearing or asymmetry. Scrape scale from the active margin when morphology is uncertain, particularly before escalating corticosteroid.

Eczema and contact dermatitis

Eczema is often less sharply demarcated and more exudative or lichenified, with an exposure pattern in contact disease. Personal atopy and intense itch support but do not prove eczema.

Papulosquamous mimics

Pityriasis rosea, secondary syphilis, lichen planus, pityriasis rubra pilaris and cutaneous lymphoma enter the differential when distribution, mucosae, palms, soles, systemic history or treatment response is atypical.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01First-lineLimited chronic plaques on trunk or limbsFirst stepFirst lineAdult plaque psoriasis amenable to topical treatment and without unstable features.

1Agree a formulation the person can use, demonstrate fingertip-unit quantities, and use emollient or soap substitute to soften scale while explaining fabric fire risk.
2Use a potent topical corticosteroid once daily plus a vitamin-D analogue once daily, applied separately morning and evening, for up to four weeks as NICE initial trunk-and-limb treatment.
3Review response, adherence, quantity, irritation and steroid adverse effects by four weeks; do not automatically continue potent steroid beyond the planned course.
4If goals are unmet, follow the NICE topical sequence or refer when extent, difficult site, distress or repeated failure makes topical-only care inadequate.

02Guttate sequenceAcute droplet eruptionAbrupt widespread small scaly lesions with a compatible post-infective history and no systemic instability.

1Confirm the pattern and examine throat, palms, soles and mucosae; pursue streptococcal or sexual-health testing only when history and findings make the result clinically useful.
2Explain that many eruptions improve over weeks to months; treat itch and dryness, and use site-appropriate topical anti-inflammatory treatment for troublesome lesions.
3Refer if diagnosis is uncertain, the eruption is extensive or persistent, or phototherapy is needed; NICE offers narrowband UVB when plaque or guttate psoriasis is not controlled topically.

03Sensitive sitesFace, flexures and genital skinThin or occluded skin where steroid adverse effects occur more readily.

1PreferredCheck for fungal or irritant coexistence and ask about pain, sexual function and preferred formulation with privacy and consent.
2Use a short course of mild or moderate potency corticosteroid once or twice daily for a maximum of two weeks under the NICE site-specific pathway; never use potent or very potent products here.
3If control remains poor or repeated treatment creates serious atrophy risk, specialist-experienced prescribing may use a topical calcineurin inhibitor twice daily for up to four weeks, off-label for psoriasis.

04EscalationSpecialist or urgent pathwayEscalationDiagnostic doubt, childhood disease, topical failure, extensive or high-impact disease, arthritis concern, or systemic upset.

1Refer all children and young people at presentation and adults meeting NICE specialist criteria; provide baseline morphology, extent, impact, treatments used and joint screen.
2Send suspected psoriatic arthritis to rheumatology as soon as suspected rather than waiting for a dermatology appointment or abnormal blood test.
3For generalised pustules or erythroderma, arrange immediate same-day specialist assessment and supportive ABCDE care; avoid unplanned systemic corticosteroid changes.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

NICE initial topical regimen for adult trunk or limb psoriasis, alongside an acceptable formulation and adherence support.

Potent topical corticosteroid plus vitamin-D analogue

Apply the potent corticosteroid thinly once daily and the vitamin-D analogue once daily at a different time, one in the morning and one in the evening, for up to 4 weeks.

Keep each product within its licence and prescribed quantity; avoid potent steroid on face, flexures or genitals, monitor atrophy, and respect vitamin-D analogue area and dose limits.

Short NICE-supported control of psoriasis where thin or occluded skin increases corticosteroid absorption and adverse-effect risk.

Mild or moderate potency topical corticosteroid for sensitive sites

Apply a thin layer once or twice daily to affected face, flexural or genital skin for no longer than 2 weeks, using the prescribed potency and quantity.

Do not substitute a potent or very potent product; reassess persistent disease for infection, contact allergy or an alternative diagnosis, and avoid indefinite repeat courses without review.

Reduces cracking and scale, improves comfort and can make application of active therapy easier, although it does not suppress psoriatic inflammation alone.

Emollient or soap substitute

Apply generously and repeatedly according to dryness, smoothing in the direction of hair growth; separate from active topical medicines by about 20 to 30 minutes when practical.

Residue on clothing, bedding, dressings and hair increases fire severity even when dry; avoid smoking and naked flames, wash fabrics frequently, and manage slip risk.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Psoriatic arthritis

Peripheral synovitis, dactylitis, enthesitis or axial inflammation can cause irreversible damage. Ask annually and at symptom change rather than waiting for severe skin disease.

Cardiometabolic burden

Severe psoriasis is associated with cardiovascular risk. NICE recommends cardiovascular risk assessment at presentation and every five years for adults whose severity has required phototherapy, systemic treatment or hospital admission.

Psychological and social harm

Stigma, sleep loss, treatment burden, sexual difficulty and low mood can be disproportionate to body surface area. High-impact sites and distress can justify specialist escalation despite limited extent.

Treatment toxicity

Continuous potent corticosteroid can cause atrophy and rebound; systemic therapies can affect marrow, liver, kidney, blood pressure, infection risk or pregnancy. Safe care depends on planned review rather than indefinite repeat prescribing.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review new topical treatment at about four weeks, checking phenotype, application site, amount used, adherence, irritation, steroid atrophy and whether the person's agreed goal has been met.
Repeat severity and impact assessment before referral, at each referral point and when judging treatment response; include difficult sites and patient-rated burden rather than body surface area alone.
Offer annual psoriatic arthritis assessment to every person with psoriasis, especially during the first ten years, and reassess sooner when joint, heel, digit or back symptoms develop.
For adults with severe psoriasis as defined by need for phototherapy, systemic treatment or hospital admission, record cardiovascular risk at presentation and at least every five years thereafter.
Review adults using intermittent potent or very potent topical corticosteroids at least annually for atrophy and other adverse effects; NICE advises annual review for children using any potency.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Scale depends on site

Classic scale is reduced by moisture in flexures and can be thick where hair or palmoplantar keratin traps it. Absence of silvery scale does not exclude psoriasis.

Colour is not activity alone

Residual hyperpigmentation or hypopigmentation can outlast inflammation. Combine colour with thickness, scale, warmth, symptoms and interval change before continuing anti-inflammatory treatment.

Guttate is a pattern

A preceding sore throat raises probability but does not make every droplet eruption psoriasis. Palmar lesions, mucosal findings, medicine timing or persistent atypical disease should prompt alternatives.

Small area can be severe

A palm, sole, genital or visible facial plaque can impair walking, work, intimacy or wellbeing more than widespread asymptomatic trunk plaques. Document the consequence explicitly.

Treatment acceptability predicts use

Ointment may suit thick dry plaques but fail on a hairy scalp or during a working day. Offer formulation choices before labelling someone non-adherent.

11Common pitfallsFrequent interpretation and management errors.

01
Calling all scaly flexural disease psoriasis without examining for fungal infection, candidiasis, irritant exposure or psoriasis at other sites.
02
Underestimating activity in deeply pigmented skin because inflammation is not bright red, or treating inactive pigment change as an ongoing flare.
03
Repeating potent corticosteroid indefinitely without a stop point, quantity review or examination for atrophy.
04
Using a low body surface area to dismiss severe genital, scalp, nail, hand or foot impact.
05
Waiting for radiographs or inflammatory markers before referring clinically suspected psoriatic arthritis.
06
Treating fever and widespread erythema as uncomplicated plaque disease instead of checking for unstable psoriasis, infection or a drug reaction.