I have fingernails with longitudinal ridges, orange discoloration, a dark subungual band just distal to the lunula, and swollen cuticles—what could be causing this and how should it be evaluated and treated?

Evaluation and Management of Fingernails with Ridges, Orange Discoloration, Dark Subungual Band, and Swollen Cuticles

This presentation requires urgent mycological confirmation before any treatment, as the combination of swollen cuticles (paronychia), nail discoloration, and ridging strongly suggests Candida nail infection, though the dark band raises concern for alternative diagnoses including melanoma that must be excluded. 1

Immediate Diagnostic Priorities

Rule Out Malignancy First

• Any dark subungual band in an adult warrants serious consideration of biopsy to exclude subungual melanoma or squamous cell carcinoma, particularly if you are over age 50. 2, 3
• The dark band is the most concerning feature in your presentation and should not be attributed to infection without histopathologic evaluation 3, 4
• Irregular, broad, or heterogeneous pigmented bands are particularly worrisome for melanoma and require dermoscopic evaluation and likely biopsy 4

Establish Infectious Etiology

• The swollen, erythematous cuticles (paronychia) combined with nail changes strongly suggest Candida infection rather than dermatophyte onychomycosis, as Candida characteristically starts proximally in the nail fold while dermatophytes begin distally 1, 5
• Candida paronychia typically affects fingernails (not toenails) and is associated with occupations requiring repeated water immersion 1
• The orange discoloration and ridging could represent Candida nail plate involvement, which causes white, green, or black marks with transverse or longitudinal furrowing 1

Mandatory Laboratory Testing

Do not initiate any antifungal treatment without mycological confirmation—approximately 50% of dystrophic nails are non-fungal despite appearing clinically identical to fungal infections. 6, 5

Required Specimens

• Collect material from the proximal nail fold (site of paronychia) and subungual debris for potassium hydroxide (KOH) preparation with microscopy 6, 5
• Submit specimens for fungal culture on Sabouraud's glucose agar, incubated at 28°C for at least 3 weeks 5
• Calcofluor white staining significantly increases sensitivity compared to KOH alone 6
• For the dark band specifically: nail matrix and nail bed biopsy with histopathologic examination using periodic acid-Schiff (PAS) staining is essential to exclude melanoma 6, 2

Common Pitfall to Avoid

• The most common cause of treatment failure is incorrect diagnosis based solely on clinical appearance without laboratory confirmation 5
• Inadequate specimen collection from superficial nail plate rather than proximal subungual debris contributes to false negatives 5

Differential Diagnosis Framework

If Candida Infection Confirmed

• Candida paronychia presents with swollen, erythematous, painful periungual skin with a prominent gap between the fold and nail plate 1
• Nail plate involvement follows, with infection commencing proximally, causing opacity, furrowing, pitting, and friability 1
• Unlike dermatophyte infections, pressure on and movement of the nail is painful with Candida 1
• Bacterial superinfection is common and may contribute to the dark discoloration 1

Alternative Non-Infectious Causes

• Lichen planus produces nail thinning with subungual hyperkeratosis and longitudinal ridging, affecting approximately 10% of cases with nail involvement 6, 5
• Psoriasis presents with nail pitting, oil drop sign, and subungual hyperkeratosis 6
• Longitudinal erythronychia (red bands) can be associated with benign tumors, malignant neoplasms, or systemic conditions like Darier disease 2, 7
• The dark band could represent subungual hemorrhage, but this must be distinguished from melanoma 3

Treatment Algorithm

If Candida Infection Confirmed (After Biopsy Excludes Malignancy)

Systemic antifungal therapy is required for Candida nail infection with paronychia:

• Itraconazole is the preferred agent for Candida species, as azoles are specifically advocated when onychomycosis is caused by Candida 8
• Pulse itraconazole dosing: 200mg twice daily for 1 week per month, for 2 pulses (2 months total) for fingernails 8
• Alternative: Fluconazole 150-300mg once weekly for 12-16 weeks for fingernails 8

Adjunctive measures for paronychia:

• Keep affected area dry and avoid prolonged water exposure 1, 5
• Apply topical povidone iodine 2% twice daily if bacterial superinfection suspected 8, 5
• Wear protective gloves during wet work to prevent recurrence 5

If Non-Infectious Cause Identified

• For lichen planus affecting less than 3 nails: intralesional triamcinolone acetonide 5-10 mg/cc for nail matrix involvement 5
• For psoriasis: topical steroids with or without vitamin D analogs for nail bed involvement 5
• Daily topical emollients to cuticles and periungual tissues to maintain hydration 5

Preventive Measures and Monitoring

• Apply daily topical emollients to cuticles and periungual tissues 8, 5
• Avoid prolonged water soaking and exposure to harsh chemicals 5
• Wear gloves while cleaning or working with chemicals 5
• If suspicious longitudinal melanonychia identified, dermoscopic follow-up every 6 months is recommended 4

Critical Red Flags

• Any dark band in a patient over 50 years requires biopsy to exclude squamous cell carcinoma or melanoma 2, 3
• Irregular, broad, or heterogeneous pigmented bands warrant immediate dermatology referral 4
• Micro-Hutchinson's sign (pigmentation extending onto periungual skin) on dermoscopy is highly suspicious for melanoma 4
• Progressive widening or darkening of the pigmented band requires urgent re-evaluation 9, 4