What causes fingernail lines or nail ridging?

What Causes Fingernail Lines (Ridging)?

Vertical ridges running from cuticle to nail tip are most commonly a normal sign of aging as the nail matrix's ability to produce smooth nails diminishes, though they can also indicate inflammatory conditions like psoriasis or lichen planus. 1

Normal Aging vs. Pathologic Causes

Vertical (Longitudinal) Ridges:

• Aging is the most common cause of vertical nail ridges, representing a benign physiological change where the nail matrix gradually loses its capacity to generate uniformly smooth nail plates 1
• Inflammatory dermatologic conditions including psoriasis and lichen planus can produce vertical ridging with associated nail thinning 1
• Brittle nail syndrome presents with longitudinal ridging combined with splitting or brittleness, potentially indicating systemic disease, medication side effects, or nail matrix damage 1

Horizontal Ridges (Beau's Lines):

• Represent temporary interruption of nail matrix activity, creating transverse grooves across the nail plate 2
• Can result from severe systemic illness, high fever, chemotherapy, or significant physiologic stress 2
• Multiple evenly-spaced Beau's lines may correlate with cyclical events like severe dysmenorrhea 3

Infectious and Inflammatory Causes

Fungal Infections (Onychomycosis):

• Present with thickening, discoloration, and friable texture of nails, more commonly affecting toenails 1
• Account for 15-40% of all nail diseases in adults 4
• Confirmation requires direct microscopy with potassium hydroxide preparation and fungal culture before initiating treatment 1

Chronic Paronychia:

• Infection and inflammation in the nail matrix area leads to proximal nail dystrophy with associated ridging 4
• Commonly occurs in patients with wet occupations or chronic moisture exposure 4
• Can cause nail thickening, ridging, and discoloration 5

Medication-Induced Ridging

• Cytotoxic drugs (taxanes, anthracyclines, fluorouracil, EGFR inhibitors) commonly cause nail abnormalities including ridging 6
• Drug-induced horizontal ridges may require temporary dose adjustment in consultation with the prescribing physician 1
• Most drug-induced nail disorders resolve after discontinuation, though complete resolution may take several years 6

Diagnostic Approach

When to Investigate Further:

• Thickening, discoloration, and friable texture warrant mycological testing with potassium hydroxide preparation and fungal culture on Sabouraud's glucose agar 1
• Inflammatory causes affecting less than 3 nails may benefit from intralesional triamcinolone acetonide 5-10 mg/cc for nail matrix involvement 1
• Examination of all 20 nail units is essential, as nail changes may indicate underlying systemic disease 7

Prevention and Management

General Nail Care:

• Daily application of topical emollients to cuticles and periungual tissues helps prevent nail problems 1
• Avoid excessive moisture exposure and wear gloves when cleaning or working with chemicals 1
• For medication-induced horizontal ridges, daily dilute vinegar soaks to nail folds twice daily for 10-15 minutes plus mid-to-high potency topical steroid ointment twice daily 1

Common Pitfall: Many clinicians assume all nail ridging represents fungal infection, but vertical ridging is most often benign aging-related change 1. Always confirm suspected onychomycosis with laboratory testing before initiating antifungal therapy, as clinical appearance alone is insufficient for diagnosis 1.