What are the differential diagnoses and recommended work‑up for a 55‑year‑old man with asymptomatic longitudinal ridges on his fingernails?

Longitudinal Nail Ridges in a 55-Year-Old Man

In an asymptomatic 55-year-old man with longitudinal fingernail ridges, this is most likely a normal age-related change requiring no workup or treatment beyond reassurance and basic nail care, unless examination reveals additional concerning features such as nail pitting, onycholysis, subungual hyperkeratosis, or paronychia that would suggest inflammatory or infectious disease. 1

Initial Clinical Assessment

The first step is examining the nails carefully for features that distinguish benign aging from pathologic conditions:

Normal aging features:

• Vertical ridges running from cuticle to nail tip without other abnormalities 1
• Hard, smooth nail texture (not soft or friable) 1
• No associated nail fold inflammation or discoloration 1

Concerning features requiring further evaluation:

• Nail pitting or onycholysis suggests psoriasis or other inflammatory conditions 2, 1
• Soft, friable texture with thickening and discoloration indicates possible fungal infection 2, 1
• Paronychia (nail fold swelling/erythema) suggests Candida infection, particularly with occupational moisture exposure 2, 1
• Subungual hyperkeratosis (debris under nail) points toward fungal infection 1
• Thinning of nail plate with longitudinal ridging may indicate lichen planus 1

Differential Diagnosis by Category

Benign/Age-Related (Most Likely)

• Normal aging: Vertical ridges are often a normal sign of aging as the nail matrix's ability to produce smooth nails diminishes 1

Inflammatory Conditions

• Psoriasis: Presents with nail pitting, onycholysis, and the majority of fingernails showing changes; often accompanied by skin plaques 2
• Lichen planus: Produces thinning of the nail plate with subungual hyperkeratosis and longitudinal ridging 1

Infectious Causes

• Dermatophyte onychomycosis: Thickening, discoloration, and friable texture; more commonly affects toenails 2
• Candida infection: Typically begins proximally with paronychia, unlike dermatophyte infections which start distally; associated with wet occupations 2, 1
• Nondermatophyte moulds: Account for approximately 5% of UK cases; suspect when previous antifungal treatment has failed repeatedly 2, 1

Systemic/Medication-Related

• Chemotherapy agents: Taxanes cause onychorrhexis with longitudinal ridging as dose-dependent toxicity 1, 3
• Connective tissue diseases: Can present with longitudinal ridging, periungual erythema, and telangiectasia 4

Recommended Workup Algorithm

For isolated longitudinal ridges with no other abnormalities:

• No laboratory testing needed 1
• Reassurance that this is a normal aging change 1
• Recommend daily topical emollients and protective nail lacquers 1, 3

If examination reveals concerning features, proceed with:

Laboratory Testing Indications

For suspected fungal infection (soft/friable texture, thickening, discoloration):

• Potassium hydroxide (KOH) preparation with microscopy as first-line screening test 1
• Fungal culture on Sabouraud's glucose agar to identify specific pathogen species 1
• Collect subungual debris from the most proximal part of the infection using a dental scraper 1
• Critical pitfall: Do not assume fungal infection without laboratory confirmation—50% of dystrophic nails are non-fungal despite similar clinical appearance 1, 5

For suspected inflammatory disease (pitting, onycholysis, thinning):

• Nail biopsy may be necessary for definitive diagnosis of lichen planus or psoriasis when clinical features are ambiguous 1

For suspected systemic conditions (brittle nails, multiple nail changes):

• Thyroid function tests to screen for thyroid dysfunction 1
• Complete blood count to check for iron deficiency anemia 1
• Consider checking albumin if Muehrcke's lines present 6

Management Recommendations

For Normal Age-Related Ridges

• Apply daily topical emollients to periungual folds, nail matrix, and nail plate to maintain hydration 1, 3
• Use protective nail lacquers to limit water loss from the nail plate 1, 3
• File nail surfaces gently with an emery board after softening in warm water 1
• Avoid trauma, nail biting, use of nails as tools, prolonged water soaking, and exposure to harsh chemicals 1, 3

For Confirmed Fungal Infection

• Treat only after mycological confirmation with systemic antifungal agents such as terbinafine or itraconazole 1
• Daily application of urea-based keratolytic cream to reduce nail thickness if needed 1

For Inflammatory Conditions

• For psoriasis or lichen planus affecting less than 3 nails: Intralesional triamcinolone acetonide 5-10 mg/cc for nail matrix involvement and topical steroids with or without vitamin D analogs for nail bed involvement 1

Critical Pitfalls to Avoid

• Do not diagnose fungal infection based on appearance alone—always obtain laboratory confirmation as 50% of dystrophic nails are non-fungal 1, 5
• Do not overlook occupational counseling—patients with chronic moisture exposure need guidance on protective measures like wearing gloves while cleaning 1
• Inadequate specimen collection from superficial nail plate rather than proximal subungual debris contributes to false negatives 1
• Do not miss medication history—chemotherapeutic agents and targeted therapies can cause nail changes 1