For my dermatology practical exam i have a spotter of nail psoriasis… please prepare me with questions and answer of moderate to hard to very hard that examiner could ask
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"nail psoriasis"
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nail psoriasis clinical features differential diagnosis treatment guideline
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https://dermnetnz.org/topics/nail-psoriasis
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Nail psoriasis spotter: examiner-style viva questions with answers
Start with a confident spotter presentation
“This is nail psoriasis, or psoriatic nail dystrophy. The likely features are irregular nail pitting, salmon-patch or oil-drop discoloration, distal onycholysis with an erythematous proximal margin, and subungual hyperkeratosis. It results from psoriasis involving the nail matrix and/or nail bed. I would examine the skin and scalp for psoriasis, joints for psoriatic arthritis, and exclude concomitant onychomycosis with nail clippings for KOH microscopy and fungal culture.”
The most diagnostic combination is irregular pitting + oil-drop/salmon patch + onycholysis with an erythematous border, especially in fingernails. Dermatology, 2-Volume Set, 5e, p. 1449.
Moderate-level questions
1. What is your diagnosis?
Nail psoriasis or psoriatic nail dystrophy.
2. Define nail psoriasis.
It is psoriasis affecting structures of the nail unit, particularly the nail matrix and/or nail bed, producing characteristic nail changes.
3. What clinical signs do you see in nail psoriasis?
- Irregular coarse pitting
- Oil-drop sign or salmon patch
- Onycholysis, often with a pink-red proximal border
- Subungual hyperkeratosis
- Nail plate thickening and crumbling
- Splinter haemorrhages
- Leukonychia
- Red spots in the lunula
- Beau lines and onychorrhexis in more extensive matrix disease
4. Which three signs are most characteristic?
- Irregular pitting
- Oil-drop or salmon-patch discoloration
- Onycholysis with an erythematous border
5. What is the oil-drop sign?
It is a translucent, irregular, yellow-orange to salmon-pink discoloration visible through the nail plate. It represents psoriatic involvement of the nail bed.
6. What is the difference between pitting in psoriasis and alopecia areata?
- Psoriasis: pits are usually large, deep, irregular, and randomly scattered.
- Alopecia areata: pits tend to be fine, shallow, regular, and geometrically distributed.
7. Which part of the nail unit produces pitting?
The nail matrix.
8. Why does pitting occur?
Focal psoriatic inflammation of the matrix causes defective keratinisation. Parakeratotic cells are shed from the growing nail plate, leaving pits.
9. What is onycholysis?
Separation of the nail plate from the nail bed, usually beginning distally or laterally.
10. What distinguishes psoriatic onycholysis from simple traumatic onycholysis?
Psoriatic onycholysis commonly has a well-demarcated erythematous or salmon-pink proximal margin. This is a useful clue to active psoriatic inflammation.
11. Is nail psoriasis limited to patients with skin psoriasis?
No. It may occasionally be the only clinical manifestation, although one should then carefully exclude fungal infection, trauma, lichen planus, and a nail-unit tumour if a single nail is involved.
12. How common is nail involvement in psoriasis?
Nail abnormalities occur in up to about 50% of patients with psoriasis at a given time, and the lifetime frequency is higher. Dermatology, 2-Volume Set, 5e, p. 1449.
Hard-level questions
13. Classify nail signs according to nail matrix versus nail-bed involvement.
| Nail matrix involvement | Nail-bed involvement |
|---|---|
| Pitting | Oil-drop/salmon patch |
| Leukonychia | Onycholysis |
| Red spots in lunula | Subungual hyperkeratosis |
| Onychorrhexis | Splinter haemorrhages |
| Beau lines | Nail-bed discoloration |
| Crumbling of nail plate |
A useful rule: matrix disease alters the nail plate as it grows; nail-bed disease alters what is visible beneath the plate. Harrison’s Principles of Internal Medicine, 22e, Clinical Features.
14. Why is nail psoriasis important beyond being a cosmetic problem?
It can cause pain, reduced fine touch, difficulty handling small objects, occupational disability, stigma, and impaired quality of life. More importantly, it is strongly associated with psoriatic arthritis, particularly enthesitis and distal interphalangeal joint disease.
15. What joint history would you take in this patient?
Ask about:
- Pain and swelling in distal interphalangeal joints
- Morning stiffness
- Dactylitis, or “sausage digit”
- Heel pain suggesting Achilles or plantar-fascia enthesitis
- Inflammatory back pain
- Reduced function or grip
- Family history of psoriasis or psoriatic arthritis
Nail involvement is a strong clinical predictor of concomitant psoriatic arthritis. Dermatology, 2-Volume Set, 5e, p. 1449.
16. Explain the association between nail psoriasis and psoriatic arthritis.
The nail apparatus is anatomically and functionally linked to the distal interphalangeal extensor tendon enthesis. This nail-enthesis relationship helps explain why nail disease is associated with distal interphalangeal arthritis and enthesitis.
17. What is the differential diagnosis of nail psoriasis?
The main differentials are:
- Onychomycosis
- Nail lichen planus
- Trauma and repetitive microtrauma
- Alopecia areata
- Chronic eczema or dermatitis
- Reactive arthritis
- Parakeratosis pustulosa, especially in children
- Acrodermatitis continua of Hallopeau
- Nail-unit tumour in isolated, persistent single-nail disease
18. How would you differentiate nail psoriasis from onychomycosis?
| Feature | Nail psoriasis | Onychomycosis |
|---|---|---|
| Pitting | Coarse, irregular, deep | Usually absent or not typical |
| Oil-drop sign | Characteristic | Absent |
| Onycholysis | Pink-red border may be seen | Common, but without typical erythematous border |
| Nail colour | Salmon-yellow areas possible | Yellow, brown, white, or black discoloration |
| Skin disease | Psoriasis elsewhere may be present | Tinea pedis often present |
| Mycology | Negative unless coinfection | Fungal elements/culture positive |
| Distribution | Several fingernails often affected | Toenails commonly affected |
In toenails, clinical distinction may be difficult, so fungal testing is important. Dermatology, 2-Volume Set, 5e, p. 1449.
19. Can onychomycosis coexist with nail psoriasis?
Yes. A damaged dystrophic nail is prone to secondary fungal infection. Do not assume all thick yellow nails in a patient with psoriasis are solely psoriatic.
20. What investigations would you perform?
Usually diagnosis is clinical, but perform:
- Nail clippings and subungual debris for KOH microscopy
- Fungal culture, and where available PAS stain of nail clippings
- Assessment for cutaneous psoriasis
- Screening clinical assessment for psoriatic arthritis
- Biopsy only if diagnosis remains uncertain, particularly for isolated single-nail disease or suspected tumour
A matrix biopsy may cause permanent nail dystrophy, so it is not routine. The DermNet diagnostic summary also recommends fungal testing because onychomycosis can coexist and matters before immunosuppressive treatment.
21. What would lichen planus of the nail look like?
Look for:
- Longitudinal ridging and fissuring
- Nail-plate thinning
- Trachyonychia
- Dorsal pterygium
- Scarring and permanent nail loss in severe disease
Dorsal pterygium is particularly suggestive of nail lichen planus rather than psoriasis.
22. What is the Koebner phenomenon and why is it relevant here?
Koebner phenomenon means development or exacerbation of psoriasis at sites of trauma. Nail biting, manicuring, picking, ill-fitting footwear, repeated occupational trauma, and aggressive nail cleaning can worsen nail psoriasis.
Very hard questions
23. Describe the pathology of nail psoriasis.
Histology varies with the affected site but may show:
- Psoriasiform epidermal hyperplasia
- Parakeratosis
- Neutrophils within parakeratotic areas
- Hypogranulosis
- Dilated capillaries in the papillary dermis
- In nail bed lesions, focal parakeratosis and neutrophilic collections can produce the clinical oil-drop and subungual hyperkeratotic changes.
Histopathology can help distinguish psoriasis from onychomycosis and other nail disorders, but biopsy is used selectively because it can permanently damage the nail. Fitzpatrick’s Dermatology, Vols. 1-2, p. 1610.
24. What is NAPSI?
NAPSI stands for Nail Psoriasis Severity Index. Each target nail is divided into four quadrants.
For each quadrant:
- Score 1 if any nail-matrix feature is present.
- Score 1 if any nail-bed feature is present.
Thus, each nail can score from 0 to 8, and all 20 nails yield a maximum score of 160. It is mainly used to quantify severity and response in clinical studies and specialist follow-up.
25. What are the limitations of NAPSI?
- It measures presence rather than the degree of each change.
- It may not reflect pain, function, or quality-of-life impact well.
- It can be time-consuming.
- It does not by itself separate active inflammation from fixed dystrophy.
26. How would you manage limited nail psoriasis?
- Explain the chronic, slow-to-improve course.
- Reduce trauma: keep nails short, avoid picking/manicures, wear gloves for wet work, use spacious footwear.
- Examine for and treat concomitant onychomycosis.
- For limited disease, use a potent topical anti-inflammatory treatment directed to the relevant site:
- Proximal nail fold for matrix disease
- Hyponychium/distal nail bed for nail-bed disease
- Consider intralesional corticosteroid by an experienced dermatologist for selected few-nail disease.
- Reassess for arthritis and functional impairment.
27. Why do topical drugs often work poorly in nail psoriasis?
The nail plate is a strong barrier, and the diseased tissue may lie in the matrix or nail bed, where topical medication penetrates poorly. Treatment must be applied to the appropriate anatomical site and requires prolonged use. Nail psoriasis is often resistant to topical therapies. Dermatology, 2-Volume Set, 5e, p. 1449.
28. When would systemic treatment be appropriate?
Consider systemic therapy when there is:
- Moderate-to-severe cutaneous psoriasis
- Significant functional impairment or pain from nail disease
- Major cosmetic or psychosocial burden
- Numerous nails involved and failure of local treatment
- Coexisting psoriatic arthritis
Systemic treatment choice should be guided by the total psoriasis burden, arthritis, comorbidity profile, pregnancy plans, infection risk, and previous therapies.
29. Which systemic therapies may improve nail psoriasis?
Conventional systemic agents and targeted therapies used for psoriasis may improve nail disease, including:
- Methotrexate
- Cyclosporine
- Acitretin in appropriate patients
- Apremilast
- Biologics targeting TNF, IL-17, IL-12/23, or IL-23 pathways
- JAK/TYK2-pathway agents in selected settings, depending on local approvals and individual risk assessment
Do not claim one agent is universally best in a viva. Say: “Choice is individualised based on skin severity, psoriatic arthritis, comorbidities, safety considerations, access, and patient preference.”
30. Why must improvement be assessed slowly?
Fingernails grow roughly 3 mm per month, and toenails grow more slowly. Visible improvement may take several months, especially in toenails. Existing damaged nail plate must grow out.
31. A patient has only one dystrophic thumbnail. Would you call it nail psoriasis immediately?
No. Isolated single-nail dystrophy needs a broader differential:
- Onychomycosis
- Trauma
- Lichen planus
- Onychopapilloma or other nail-unit tumour
- Bowen disease/squamous cell carcinoma
- Subungual melanoma if pigmentation is present
I would examine the rest of the skin and nails, perform fungal testing, use dermoscopy where appropriate, and consider specialist nail-unit biopsy if a tumour cannot be excluded.
32. What dermoscopic clues may support nail psoriasis?
Reported dermoscopic features include:
- Irregular coarse pits
- Salmon patches
- Erythematous border of onycholysis
- Splinter haemorrhages
- Dilated capillaries in the hyponychium
A 2024 systematic review specifically evaluated dermoscopic features of nail psoriasis, PMID 38520074. This supports dermoscopy as an adjunct, not a replacement for mycological testing when fungus is possible.
33. Give a concise examiner-level distinction between nail psoriasis and reactive arthritis.
Both can produce psoriasiform nail changes, including subungual hyperkeratosis and onycholysis. In reactive arthritis, look for the systemic context: preceding genitourinary or gastrointestinal infection, asymmetric oligoarthritis, enthesitis, conjunctivitis/uveitis, urethritis, circinate balanitis, and keratoderma blennorrhagica.
34. What examination would you do after identifying nail psoriasis?
- Inspect all 20 nails
- Examine scalp, ears, umbilicus, natal cleft, elbows, knees, palms and soles for psoriasis
- Look for plaques and assess body surface involvement
- Examine joints, especially DIP joints
- Look for dactylitis and enthesitis
- Check feet for tinea pedis and onychomycosis
- Ask about functional limitation, work impact, pain, and psychosocial distress
High-yield one-line answers to memorise
- Pitting = nail matrix involvement.
- Oil-drop sign = nail-bed psoriasis.
- Onycholysis with a red proximal border strongly suggests psoriasis.
- Coarse irregular pits suggest psoriasis; fine regular pits suggest alopecia areata.
- Always exclude coexisting onychomycosis with nail clippings.
- Nail psoriasis is a clinical clue to psoriatic arthritis.
- Nail disease responds slowly because the nail plate must grow out.
- Do not biopsy routinely: matrix biopsy can cause permanent dystrophy.
- Isolated single-nail dystrophy requires exclusion of tumour.
- Avoid trauma because of Koebnerisation.
A polished final answer if the examiner asks: “How will you manage this patient?”
“I would first assess the number of nails involved, functional and psychosocial impact, associated skin psoriasis, and symptoms or signs of psoriatic arthritis. I would obtain nail clippings for fungal microscopy and culture because onychomycosis can mimic or coexist with nail psoriasis. I would advise trauma avoidance and nail care. For limited disease, I would use site-directed topical therapy or consider intralesional corticosteroid in selected cases. If nail disease is extensive, disabling, treatment-resistant, associated with significant skin disease, or accompanied by psoriatic arthritis, I would refer for systemic psoriasis therapy.”
Recent systematic reviews found in the last two years focus on dermoscopy and laser therapies, not findings that overturn the core clinical approach above: dermoscopy review, PMID 38520074 and laser review, PMID 38858829.
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