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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Nail signs of psoriasis, melanoma and systemic disease

Dermatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Nail sign with acute systemic disease

New clubbing with hypoxia, haemoptysis or severe breathlessness, or splinter haemorrhages with fever, murmur, embolic features or sepsis, may signal serious cardiopulmonary disease or infective endocarditis.

Action: Assess observations and systemic stability immediately and use the relevant acute respiratory, cardiac, sepsis or endocarditis pathway; cosmetic nail treatment must not delay investigation.

Overview

Read nail morphology as a diagnostic clue without overclaiming specificity, recognise melanoma and infection warnings, and connect psoriasis, clubbing, koilonychia and other changes to proportionate investigation.

Nail signs arise from different anatomy. Matrix disease changes the plate as it is formed, producing pits, ridges, Beau lines or longitudinal pigment. Nail-bed disease causes onycholysis, oil-drop change, subungual material or splinter haemorrhage. Proximal and lateral folds reveal inflammation, infection or pigment spread. Fingernails take roughly six months and toenails twelve to eighteen months to replace, so a groove's distance from the cuticle can place a past event approximately but cannot date it precisely without individual growth rate.

Psoriasis is a common unifying diagnosis, yet fungus frequently coexists and must be confirmed before systemic antifungal treatment. Melanonychia deserves an inclusive approach: benign racial or physiological bands are common in people with deeply pigmented skin and often affect several nails, but this must never become reassurance for a changing irregular single band. Conversely, automatic urgent biopsy of every stable narrow band can cause avoidable permanent dystrophy. Dermoscopy, serial measurement and specialist triage balance those harms.

Practice

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DermatologyOriginal SBA

Changing single nail band

A 52-year-old has a new dark longitudinal thumbnail band that has widened proximally, contains irregular colours and now extends onto the proximal nail fold. What is the best action?

Choose one answer, then submit
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • Primary Care Dermatology Society longitudinal melanonychiaInclusive risk assessment, dermoscopy, surveillance and urgent biopsy features.
  • NICE NG12 suspected skin cancer recommendationsUrgent referral framework for suspected melanoma and squamous malignancy.
  • NICE CG153 psoriasis recommendationsNail assessment, difficult-site burden and psoriasis treatment context.
  • NHS nail problemsCommon nail changes and systemic reasons to seek medical assessment.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Systemic associations are clues, not shortcuts. Clubbing can accompany lung cancer, bronchiectasis, interstitial lung disease, cyanotic heart disease and inflammatory bowel or liver disease. Koilonychia prompts iron assessment when history supports it. Terry or half-and-half nails and transverse lines occur with chronic or severe illness but have limited specificity. A good nail examination therefore leads to a focused history, physical examination and selected tests rather than a chart of one-to-one diagnoses.

Key points

  • Nails record matrix, bed and systemic events slowly; name the structure and pattern before assigning a disease, because most single signs are not specific.
  • Psoriasis causes regular pitting, oil-drop or salmon patches, subungual hyperkeratosis and onycholysis with an erythematous border, and may exist without obvious skin plaques.
  • A new evolving irregular longitudinal melanonychia band in one adult nail, especially with periungual Hutchinson pigment or nail destruction, must be assessed urgently for melanoma.
  • Longitudinal pigmentation across several nails can be physiological in darker skin or drug related, but change, symptoms and one-nail asymmetry remain important in every skin tone.
  • True clubbing includes loss of the nail-fold angle, increased fluctuation and bulbous distal phalanx; it triggers cardiopulmonary, gastrointestinal and inflammatory assessment rather than a cosmetic referral.
  • Koilonychia can accompany iron deficiency, while Beau lines mark temporary matrix arrest after severe illness or stress; neither establishes the systemic diagnosis by itself.
  • Splinter haemorrhages are commonly traumatic and distal, but multiple proximal lesions plus fever, murmur or embolic features require urgent endocarditis assessment.
  • Onycholysis occurs with psoriasis, fungus, trauma, thyroid disease and medicines; clip, examine and sample rather than inferring cause from separation alone.

Aetiology

01

Matrix inflammation

Psoriasis, lichen planus and systemic growth arrest alter plate formation, producing pits, ridges, grooves, thinning or pigment lines.

02

Nail-bed disease

Psoriasis, fungus, trauma and tumours change adhesion, keratin and vasculature beneath the plate, creating onycholysis, debris or haemorrhage.

03

Melanocyte activation or proliferation

Physiological pigmentation, medicines, inflammation, naevi and melanoma can each generate longitudinal melanin from the nail matrix.

04

Systemic tissue signalling

Cardiopulmonary and inflammatory disease can remodel distal digits, while severe illness temporarily arrests matrix growth and iron deficiency alters plate structure.

Pathophysiology

  1. 1
    Matrix defects grow distally

    Once plate is formed it cannot repair, so pits, grooves and pigment migrate toward the free edge at the individual's nail-growth rate.

  2. 2
    Bed adhesion is disrupted

    Inflammation, keratin accumulation or trauma separates plate from bed, allowing air, organisms and debris into the onycholytic space.

  3. 3
    Melanin enters the plate

    A matrix melanocyte population deposits pigment into growing keratin, producing a longitudinal band whose width and regularity reflect the source.

  4. 4
    Distal soft tissue expands

    Clubbing involves vascular and connective-tissue change beneath the nail bed, increasing fluctuation and flattening the normal proximal-fold angle.

Clinical features and red flags

Psoriatic matrix signs

Regular pits, crumbling and leukonychia arise from matrix inflammation and may accompany scalp, natal-cleft, umbilical or extensor psoriasis.

Psoriatic bed signs

Oil-drop colour, subungual hyperkeratosis and onycholysis with a salmon-pink proximal margin support nail-bed psoriasis.

Suspicious melanonychiaRed flag

A new single band with irregular lines, colour variation, proximal widening, periungual extension or dystrophy raises nail-unit melanoma concern.

True clubbing

Loss of the normal nail-fold angle, increased nail-bed fluctuation, bulbous tips and absent Schamroth window support clubbing when assessed together.

Koilonychia

A thin concave spoon-shaped plate can accompany iron deficiency but also occurs after trauma, exposure or as an individual trait.

Beau lines

Transverse depressions at similar levels across several nails record temporary matrix growth arrest after systemic illness, chemotherapy or severe stress.

Splinter haemorrhagesRed flag

Thin longitudinal red-brown lines are often distal and traumatic; multiple proximal lesions with fever or embolic features raise endocarditis concern.

Red flags requiring action

  • A new or changing single-nail longitudinal pigmented band with irregular width or colour, proximal widening, Hutchinson sign, nail dystrophy, bleeding, ulceration or a subungual mass requires urgent suspected melanoma assessment.

Investigations

  1. 01
    All-nail and skin examinationFirst step
    Why
    Define number, symmetry, anatomical structure and associated skin or joint phenotype.
    Interpretation and limitations
    Several similar nails with classic skin psoriasis support a field disorder; a progressive single nail needs focal tumour, trauma or infection assessment.
  2. 02
    Nail dermoscopy
    Why
    Assess pigment lines, nail-bed vascular features and an onycholysis margin under magnification.
    Interpretation and limitations
    Irregular line thickness, colour, spacing and periungual spread increase melanoma concern, but dermoscopy cannot replace specialist biopsy when clinical suspicion persists.
  3. 03
    Serial photography and measurement
    Why
    Determine whether a low-risk pigmented band is stable or evolving under a specialist plan.
    Interpretation and limitations
    Use calibrated width, proximal and distal landmarks, consistent lighting and a short defined review interval; undocumented observation is not safe surveillance.
  4. 04
    Nail clipping and subungual mycology
    Why
    Identify fungal infection where psoriasis, trauma and onychomycosis overlap.
    Interpretation and limitations
    Collect proximal diseased plate and debris before systemic antifungal treatment; positive fungus can coexist with psoriasis and does not explain a suspicious pigment band automatically.
  5. 05

Differential diagnosis

01

Onychomycosis

Subungual debris and colour can mimic psoriasis, so representative microscopy and culture are needed before prolonged oral antifungal treatment.

02

Traumatic dystrophy

Footwear, sport, picking or repetitive work produces local ridges, haemorrhage and onycholysis with a distribution matching mechanical exposure.

03

Physiological melanonychia

Stable regular bands in several nails are common in darker skin and differ from a new widening irregular single-nail outlier.

04

Subungual haematoma

Trauma-related blood fails to form orderly longitudinal matrix lines and should migrate distally with plate growth, while persistent atypical pigment needs review.

05

Periungual squamous malignancy

A persistent verrucous, ulcerated or destructive nail-fold lesion can mimic wart or infection and requires biopsy when treatment fails or invasion is suspected.

Management

01Pigmented bandTriage melanonychia without skin-tone biasFirst stepLongitudinal brown or black pigment appears in one or more nails.+
  1. 1Ask onset, change, trauma, medicines, pregnancy, family pigmentation and melanoma history, then examine every nail, skin and mucosa and photograph with consent.
  2. 2Refer urgently a new or changing irregular single band, proximal widening, Hutchinson sign, dystrophy, bleeding or mass through the suspected melanoma pathway.
  3. 3For a genuinely low-risk stable pattern, specialist-led dermoscopic surveillance uses calibrated images and a defined interval; any evolution converts to biopsy assessment.
02Psoriatic nailSeparate inflammation from fungusPitting, oil-drop change, hyperkeratosis or onycholysis suggests psoriasis.+
  1. 1Look for scalp, ear, umbilical, natal-cleft and extensor disease and ask about inflammatory joint symptoms and functional nail pain.

Complications

01

Delayed melanoma diagnosis

Attributing an evolving pigmented band to ethnicity, trauma or fungus can allow nail-unit melanoma to invade before targeted biopsy.

02

Missed systemic disease

Failure to investigate true new clubbing or infective endocarditis features delays treatment of potentially life-threatening underlying disease.

03

Pain and functional loss

Psoriatic, fungal and structural dystrophy can impair grip, walking, footwear tolerance and fine manual tasks despite small body-surface area.

04

Procedure-induced dystrophy

Poorly planned matrix biopsy, avulsion or destructive treatment can permanently split or deform a nail without obtaining diagnostic tissue.

Monitoring and follow-up

  • For a monitored pigmented band, record calibrated width, colour pattern, proximal widening and periungual pigment at every defined specialist review.
  • Track psoriatic nail growth and function over at least six months and reassess mycology before systemic antifungal treatment or unexplained deterioration.
  • Follow new clubbing through a named clinician until a plausible cause is identified or an appropriate specialist has accepted ongoing assessment.
  • After iron replacement, document haematological response and investigation of blood loss; normal nail shape may take an entire growth cycle to return.
  • Following nail-unit biopsy, monitor infection, pain, histology, permanent growth change and whether further excision or oncology discussion is required.

Special situations

Structure locates disease

Pits originate in matrix, while oil-drop change and onycholysis arise in bed; identifying anatomy narrows both diagnosis and biopsy target.

Several bands can be normal

Physiological melanonychia commonly affects multiple nails in darker skin, but a changing outlier still receives the same melanoma scrutiny.

Clubbing is a composite sign

One curved nail is not enough; angle loss, fluctuation, distal enlargement and distribution together make the finding more reliable.

Nails timestamp imperfectly

A Beau line moves distally as nail grows, offering an approximate record of systemic stress but not a precise calendar date.

Coexistence is common

Psoriatic dystrophy creates spaces in which fungus can grow, so a positive sample does not erase inflammatory signs or joint screening.

Common pitfalls

  1. 01

    Reassuring a changing single pigmented band solely because the patient has dark skin.

  2. 02

    Urgently biopsying every stable multi-nail physiological band without specialist dermoscopic triage.

  3. 03

    Diagnosing systemic disease from one nonspecific nail sign without history and examination.

  4. 04

    Calling thick yellow psoriatic nails fungal and prescribing oral terbinafine without sampling.

  5. 05

    Treating splinter haemorrhages cosmetically when fever, murmur or embolic signs are present.

  6. 06

    Performing an unplanned nail-matrix biopsy without consent for permanent dystrophy and histological orientation.

  • Nail-matrix biopsy can permanently alter growth and should be planned by a specialist who can target the lesion and orient histology correctly.
    • Nail-unit biopsy
    Why
    Establish melanoma, inflammatory matrix disease or another structural diagnosis when the result changes management.
    Interpretation and limitations
    A nail specialist selects matrix, bed or fold target and counsels about pain, scar and permanent dystrophy; superficial clipping cannot exclude a matrix melanoma.
  • 06
    Cardiopulmonary assessment for clubbing
    Why
    Identify a serious thoracic, cardiac or inflammatory cause of true new clubbing.
    Interpretation and limitations
    Use symptoms, oxygen saturation, chest examination and indicated radiography or specialist testing; normal initial observations do not make persistent new clubbing cosmetic.
  • 07
    Full blood count and ferritin
    Why
    Assess iron deficiency when koilonychia or blood-loss history supports it.
    Interpretation and limitations
    Interpret ferritin with inflammation and investigate the cause of deficiency; spooning alone does not justify indefinite iron or prove gastrointestinal bleeding.
  • 08
    Blood cultures and endocarditis pathway
    Why
    Investigate systemic infection when splinter haemorrhages accompany fever, murmur or embolic findings.
    Interpretation and limitations
    Obtain appropriate cultures before antibiotics when this does not delay sepsis treatment, and arrange echocardiography and specialist care from the overall probability.
    • 2
    Obtain representative fungal mycology before oral antifungal treatment when thickening or colour could be infection, recognising that both diagnoses can coexist.
  • 3Treat within the psoriasis pathway according to skin, nail and joint burden; isolated severe nail disease can justify dermatology referral even when skin area is small.
    • 03Clubbing or systemic clueInvestigate the person rather than the plateTrue clubbing, koilonychia, Beau lines or widespread new nail change has no obvious local explanation.+
    1. 1Confirm morphology and timeline, then take respiratory, cardiac, gastrointestinal, bleeding, dietary, medicine and severe-illness history with a directed full examination.
    2. 2Use oxygen saturation, chest imaging, full blood count, ferritin, liver, renal, thyroid or other tests only as supported by that clinical pattern.
    3. 3EscalationEscalate hypoxia, haemoptysis, sepsis, murmur or embolic signs immediately and arrange follow-up ownership for less acute unexplained clubbing or systemic change.
    04Single destructive nailExclude tumour before repeated treatmentOne nail develops progressive dystrophy, ulceration, bleeding, pain or a subungual mass.+
    1. 1Document duration and prior trauma or treatment, remove polish and examine plate, bed, folds and regional nodes without curetting a possible tumour.
    2. 2Arrange urgent dermatology or nail-surgery assessment for dermoscopy, imaging where indicated and properly targeted biopsy.
    3. 3Do not use repeated antibiotics, antifungals or avulsion as diagnostic substitutes, and ensure histology results and wound care have named clinical ownership.