6.2 Nail Disorders, Onychomycosis & Nail Unit Tumours
Key Takeaways
- Fingernails grow about 3 mm per month and are replaced in about 6 months, while toenails grow about 1 mm per month and take 12 to 18 months to regrow.
- Oral terbinafine 250 mg daily for about 6 weeks for fingernails and 12 weeks for toenails is first-line for dermatophyte onychomycosis after mycological confirmation.
- Hutchinson sign, the spread of pigment from a longitudinal melanonychia onto the nail fold, is a warning sign of subungual melanoma and needs a nail matrix biopsy.
- Terry nails (white proximal nail with a narrow distal pink band) suggest cirrhosis, heart failure, or diabetes, whereas half-and-half nails suggest chronic kidney disease.
- A glomus tumour causes severe pinpoint nail pain, cold sensitivity, and a bluish spot under the nail, and multiple glomus tumours are associated with neurofibromatosis type 1.
Last updated: September 2026
6.2 Nail Disorders, Onychomycosis & Nail Unit Tumours
Nail Anatomy and Growth
- The nail matrix forms the nail plate: the proximal matrix makes the upper (dorsal) plate, and the distal matrix makes the lower (ventral) plate. The lunula is the visible part of the distal matrix.
- The nail bed lies under the plate and ends at the hyponychium. The proximal nail fold and cuticle seal the space above the matrix.
- Growth: fingernails about 3 mm per month (full replacement in about 6 months); toenails about 1 mm per month (12–18 months).
The site of a sign tells you where the problem lies. Pitting and leukonychia come from the matrix. Onycholysis and subungual hyperkeratosis come from the nail bed.
Key Nail Signs
| Sign | Description | Main Causes |
|---|---|---|
| Pitting | Small depressions in the plate | Psoriasis, alopecia areata, eczema |
| Beau lines | Transverse grooves across all nails | Temporary matrix arrest after severe illness, chemotherapy; distance from cuticle dates the event |
| Onychomadesis | Proximal separation and shedding of the plate | Severe matrix arrest, for example after hand, foot, and mouth disease |
| Koilonychia | Spoon-shaped nails | Iron deficiency; normal in infants |
| Clubbing | Loss of the angle between nail fold and plate (over 180°); positive Schamroth window test | Lung cancer, bronchiectasis, cystic fibrosis, cyanotic heart disease, inflammatory bowel disease |
| Terry nails | White proximal nail with a narrow distal pink-brown band | Cirrhosis, heart failure, diabetes |
| Half-and-half (Lindsay) nails | Proximal half white, distal half red-brown | Chronic kidney disease |
| Muehrcke lines | Paired white transverse bands that fade on pressure (nail bed) | Hypoalbuminaemia, chemotherapy |
| Mees lines | True white transverse bands in the plate that grow out | Arsenic, thallium, other poisoning |
| Splinter haemorrhages | Thin red-brown longitudinal lines | Trauma (most common), psoriasis, infective endocarditis |
| Onycholysis | Distal separation of plate from bed | Psoriasis, trauma, onychomycosis, thyroid disease, photo-onycholysis (tetracyclines, psoralens) |
| Green nail | Green-black discolouration | Pseudomonas aeruginosa (pyocyanin) under onycholytic nails |
| Yellow nail syndrome | Thick, slow-growing yellow nails | With lymphoedema and pleural effusion or chronic sinusitis |
| Dorsal pterygium | Proximal nail fold fused to the matrix, splitting the nail | Lichen planus (scarring) |
| Triangular lunulae | Triangle-shaped lunulae | Nail-patella syndrome (LMX1B), with absent patellae, iliac horns, and nephropathy |
Onychomycosis
- Causes: dermatophytes, mainly Trichophyton rubrum, cause most toenail infections. Non-dermatophyte moulds (Scopulariopsis, Fusarium) and Candida (especially in fingernails with chronic paronychia or chronic mucocutaneous candidiasis) cause the rest.
- Patterns: distal lateral subungual (the most common); proximal subungual (suggests immunosuppression, including HIV); white superficial (T. interdigitale); endonyx; and total dystrophic.
- Confirm before treating: potassium hydroxide (KOH) microscopy with culture, fungal PCR, or nail clipping histology with PAS stain. About half of dystrophic nails are not fungal (psoriasis, trauma).
- Treatment:
- Oral terbinafine 250 mg daily: about 6 weeks for fingernails and 12 weeks for toenails. It is first-line for dermatophytes. Check liver function at baseline, and warn about taste disturbance and rare liver injury.
- Itraconazole pulse therapy (200 mg twice daily for 1 week each month; 2 pulses for fingernails, 3 for toenails): useful for Candida and some moulds. Watch for drug interactions and avoid in heart failure.
- Topical lacquers (amorolfine 5%, ciclopirox 8%): for limited distal disease without matrix involvement, or combined with oral therapy.
- Adjuncts: debridement, treatment of tinea pedis, and footwear hygiene to prevent relapse.
Paronychia
| Type | Features | Management |
|---|---|---|
| Acute | Painful red swelling of the nail fold, often with pus, after minor trauma | Staphylococcus aureus or streptococci; warm soaks, drainage, anti-staphylococcal antibiotic |
| Chronic | Swollen fold with loss of the cuticle for over 6 weeks, in wet work (cooks, cleaners) | Mainly an irritant or allergic dermatitis with secondary Candida; avoid wet work, topical steroid plus antifungal |
| Herpetic whitlow | Grouped painful vesicles on a finger | HSV; do not incise; oral antiviral |
Inflammatory Nail Disease
- Nail psoriasis: pitting, oil-drop spots, onycholysis, subungual hyperkeratosis, and splinter haemorrhages. Severity is scored with the NAPSI. Nail disease predicts psoriatic arthritis. Treatment: intralesional triamcinolone, topical steroid with calcipotriol, and for severe disease systemic agents (IL-17, IL-23, and TNF inhibitors are effective).
- Nail lichen planus: thinning, ridging, and fissuring, which can lead to dorsal pterygium and permanent nail loss. Treat early with intralesional or systemic corticosteroids.
- Trachyonychia ("twenty-nail dystrophy"): rough, sandpaper-like nails in alopecia areata, lichen planus, psoriasis, or on its own.
Longitudinal Melanonychia and Subungual Melanoma
A brown-black longitudinal band arises from melanocyte activation (ethnic in darker skin types, drugs, trauma, Laugier-Hunziker syndrome), a lentigo or naevus, or melanoma.
Warning features (ABCDEF rule):
| Letter | Feature |
|---|---|
| A | Age (peak in the 5th to 7th decades) and African, Asian, or Native American background (nail melanoma forms a higher share of melanomas) |
| B | Band: brown-black, breadth ≥ 3 mm, irregular or blurred borders |
| C | Change: rapid increase in width, or failure of a dystrophic nail to improve |
| D | Digit: thumb, big toe, and index finger most often; a single digit is more worrying than many |
| E | Extension of pigment onto the nail fold (Hutchinson sign) |
| F | Family or personal history of melanoma or dysplastic naevi |
Pseudo-Hutchinson sign: pigment seen through a thin, transparent cuticle, or periungual pigment in Laugier-Hunziker or ethnic pigmentation. Dermoscopy of melanoma shows irregular lines of varying colour, thickness, and spacing with loss of parallelism. A suspicious band needs a nail matrix biopsy (tangential excision of the matrix at the band's origin) by a trained operator. A subungual haematoma shows red-purple globules and grows out distally over weeks.
Nail Unit Tumours
| Tumour | Key Points |
|---|---|
| Glomus tumour | Severe pinpoint pain, cold sensitivity, bluish-red spot under the nail; Love pin test and Hildreth test; multiple lesions in NF1; MRI and excision |
| Subungual exostosis | Firm nodule lifting the nail of the big toe in young people; diagnosed on X-ray |
| Digital myxoid (mucous) cyst | Translucent cyst on the proximal nail fold, linked to distal interphalangeal osteoarthritis; causes a longitudinal groove |
| Onychomatricoma | Yellow thickened band with finger-like projections from the matrix |
| Bowen disease / squamous cell carcinoma | Persistent warty or eroded periungual lesion, often HPV 16; the most common malignant nail tumour |
| Subungual melanoma | Usually acral lentiginous type; see warning signs above |
Test Your Knowledge
A 60-year-old man has a 5 mm wide, irregular brown-black longitudinal band on his left thumbnail that has widened over a year, with pigment spreading onto the proximal nail fold. What is the most appropriate next step?
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Test Your Knowledge
Onychomycosis of the big toenail caused by Trichophyton rubrum is confirmed by culture. What is the standard first-line oral regimen?
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B
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D
Test Your Knowledge
A patient with a long history of alcohol misuse has nails that are white over most of the plate, with a narrow pink-brown band at the distal edge. Which condition do these nails most suggest?
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B
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D
Test Your Knowledge
A 40-year-old woman has severe stabbing pain in one fingertip, worse in cold water, and a small bluish spot visible under the nail plate. What is the most likely diagnosis?
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B
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D