How to Diagnose and Manage Nail Psoriasis vs Onychomycosis

1. Diagnosis Criteria

🔵 A. Nail Psoriasis – Diagnostic Criteria

Clinical Diagnosis (no single gold standard). Diagnosis is based on classic nail findings + history of psoriasis.

Major Nail Features

1. Pitting

2. Oil-drop (salmon patch) discoloration

3. Onycholysis with erythematous border

4. Subungual hyperkeratosis (psoriatic type: chalky, white)

5. Nail crumbling / roughness

6. Leukonychia
   

Supportive Features

• Current or past cutaneous psoriasis

• Psoriatic arthritis

• Family history of psoriasis

• Negative fungal studies (KOH/PAS/culture)
  

Diagnostic Tools

• Clinical exam = primary

• Dermoscopy (onycholysis with reddish margin, irregular pitting)

• PAS stain of nail clipping (to rule out fungus)

• Nail matrix biopsy (rarely needed)
  

🟢 B. Onychomycosis – Diagnostic Criteria

Must confirm fungus before systemic therapy.

Major Criteria

(At least 1 required)

1. Positive KOH (hyphae or yeast)

2. Positive fungal culture

3. Positive PAS stain (most sensitive)

4. PCR positive for dermatophyte or non-dermatophyte mold
   

Clinical Features

• Nail thickening (onychauxis)

• Whitish/yellowish discoloration

• Subungual debris (keratinous, dense)

• Distal-lateral subungual onychomycosis (most common)

• Proximal white onychomycosis (HIV indicator)

• Total dystrophic onychomycosis
  

Supportive Features

• Tinea pedis/manuum

• Household fungal infection

• Slow progression

• Usually no pitting, no oil-drop
  

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2. Management

🔵 A. Management of Nail Psoriasis

1. Mild Disease (<3 nails, cosmetic concern only)

Topical therapy (first-line)

• High-potency topical steroid (Clobetasol 0.05%)

• Calcipotriol (vitamin D analog)

• Tazarotene 0.1% gel

• Tacrolimus 0.1% ointment (safe for long-term use)
  

2. Moderate Disease

Intralesional therapy

• Triamcinolone acetonide 2.5–10 mg/mL

  • Inject into nail matrix or nail bed every 4–8 weeks
    

3. Severe Disease / Multiple Nails / Functional Impairment

Systemic therapy (depending on comorbid psoriasis)

• Methotrexate 7.5–20 mg weekly

• Cyclosporine 2.5–5 mg/kg/day

• Acitretin 25–50 mg/day (great for hyperkeratosis)

• Biologic therapy (BEST evidence)

  • IL-17 inhibitors: Secukinumab, Ixekizumab

  • TNF-α inhibitors: Adalimumab, Etanercept

  • IL-23 inhibitors: Guselkumab, Risankizumab

Biologics are most effective overall for severe nail psoriasis.

4. Supportive care

• Avoid trauma & excessive manicure

• Keep nails short

• Treat concomitant fungal infection

• Moisturizers & protect hands (gloves)
  

🟢 B. Management of Onychomycosis

1. Confirm Diagnosis First

Systemic antifungal therapy should not be started without confirmation.

• KOH preparation – rapid bedside test

• PAS stain – highest sensitivity

• Fungal culture – identifies organism (takes longer)

Exam pearl: Helps differentiate from nail psoriasis or trauma.

2. Systemic Antifungal Therapy (First-line)

A. Terbinafine – Drug of Choice

Terbinafine (250 mg) 1×1 po pc

• Fingernails: 6 weeks

• Toenails: 12 weeks

Rationale:

• Fungicidal against dermatophytes

• Highest cure rate

Monitoring:

• Baseline liver function test (LFT)

• Repeat if prolonged therapy or symptoms

B. Itraconazole – Alternative

Pulse therapy (preferred for fingernails)

Itraconazole (100 mg) 2×2 po pc for 1 week/month

• Fingernails: 2 cycles

• Toenails: 3–4 cycles

Continuous therapy (off-label for fingernails)

Itraconazole (100 mg) 1×2 po pc

• Fingernails: 6 weeks

• Toenails: 12 weeks

(Equivalent to Itraconazole 200 mg 1×1 po pc)

C. Fluconazole (Alternative, off-label)

Fluconazole (150–300 mg) 1×1 weekly po

• Fingernails: 3–6 months

• Toenails: longer duration required

Indication:

• Candida infection

• When terbinafine cannot be used
  

3. Topical Therapy (Only Mild Disease)

Indications:

• <50% nail involvement

• No nail matrix involvement

Options:

• Efinaconazole 10% solution daily × 48 weeks

• Ciclopirox 8% lacquer daily × 48 weeks

• Tavaborole 5% daily

Limitation: Lower efficacy, especially for toenails

4. Adjunctive Measures

• Nail debridement to improve drug penetration

• Treat concomitant tinea pedis/manuum

  • Terbinafine cream (1%) 1×1 topical for 2–4 weeks

• Keep nails dry

• Avoid occlusive footwear and trauma

5. Prevention

• Do not share nail instruments

• Keep feet dry

• Use antifungal powder if recurrent

• Treat close contacts if fungal infection present

  
  

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3. High-Yield Table: Nail Psoriasis vs Onychomycosis

Feature	Nail Psoriasis	Onychomycosis
Etiology	Immune-mediated psoriasis	Fungal infection (dermatophytes, yeast, mold)
Pitting	Common	Rare / absent
Oil-drop sign	Characteristic	Never
Subungual hyperkeratosis	Chalky, white	Yellow-brown, crumbly
Discoloration	Yellow-red (salmon patch)	Yellow-white-brown
Onycholysis	Present with erythematous margin	Present but no red border
Nail plate	Crumbling, ridging	Thickened, brittle
Pain	Usually mild	Often none unless severe
Associated diseases	Skin psoriasis, PsA	Tinea pedis, immunosuppression
Diagnosis	Clinical + rule out fungus	Must confirm fungus (KOH/PAS/culture)
First-line treatment	Topical steroid + vit D	Oral terbinafine
Response time	Slow (6–12 months)	Faster (3–6 months for hands)
Systemic therapy	MTX, cyclosporine, biologics	Terbinafine, itraconazole
Occurrence	Chronic autoimmune	Infectious, contagious

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Exam Pearls

1. Pitting + oil-drop → Psoriasis

2. Confirm fungus before systemic antifungals

3. Terbinafine = best for fungal infection

4. Biologics = best for severe nail psoriasis

5. Psoriasis may mimic fungus → always rule out with KOH/PAS

6. Onycholysis with erythematous border → Psoriasis

7. Fungal debris is yellow-brown; psoriatic debris is white-chalky