What are the causes, evaluation, and management of leukonychia (white lines on the nails)?

White Lines in Nails (Leukonychia)

White lines on the nails (leukonychia) require systematic evaluation to distinguish between benign cosmetic variants and serious systemic disease, with management directed at the underlying cause rather than the nail appearance itself.

Classification and Diagnostic Approach

Leukonychia must be classified both anatomically and morphologically to guide evaluation 1:

Anatomical Classification

• True leukonychia: Abnormality within the nail plate itself
• Apparent leukonychia: Abnormality of the nail bed showing through the plate
• Pseudoleukonychia: Surface-only changes (external deposits)

Morphological Patterns

• Transverse lines (Mees' lines, Muehrcke's lines)
• Total/partial (Terry's nails, Lindsay's nails)
• Longitudinal streaks
• Punctate (leukonychia punctata)

Key Diagnostic Distinction

The single most important clinical test is applying pressure to the nail: True leukonychia remains white under pressure because the abnormality is in the nail plate, while apparent leukonychia blanches because the problem is in the vascular nail bed 1.

Causes by Category

Benign/Idiopathic

• Trauma (most common cause - manicure habits, minor injury)
• Hereditary leukonychia (rare, often PLCδ1 gene mutations) 2, 3
• Idiopathic true leukonychia (benign, no treatment needed)

Systemic Disease (Apparent Leukonychia)

• Hypoalbuminemia (Muehrcke's lines - paired transverse bands that blanch with pressure)
• Chronic kidney disease (Lindsay's nails - proximal white, distal pink)
• Liver cirrhosis (Terry's nails - proximal white, narrow distal pink band)
• Congestive heart failure

Toxic Exposures

• Chronic arsenic poisoning - can cause leukonychia totalis with Mees' lines 4
• Heavy metals (lead, thallium)
• Chemotherapy agents

Infectious

• Fungal infection (onychomycosis) - though this typically causes yellow-white discoloration rather than true white lines [@1-10@]

Other

• Nutritional deficiencies (zinc, vitamin B12) 3
• Thyroid disorders 3
• Psoriasis, lichen planus 5

Evaluation Algorithm

1. History: Duration, progression, trauma history, systemic symptoms, medications, occupational exposures, family history

2. Physical examination:

   • Apply pressure to determine true vs. apparent leukonychia
   • Assess pattern (transverse, longitudinal, total, punctate)
   • Examine all nails and skin
   • Look for systemic signs (edema, jaundice, pallor)

3. Laboratory testing (when systemic disease suspected):

   • Complete blood count
   • Comprehensive metabolic panel (albumin, liver function, creatinine)
   • Thyroid function tests
   • If toxic exposure suspected: urine/hair/nail arsenic levels 4
   • Vitamin B12, zinc levels if deficiency suspected

4. Nail-specific testing:

   • Fungal culture and microscopy if onychomycosis suspected 6
   • Nail biopsy rarely needed (only for unclear hereditary cases or malignancy concern)

Management

True Leukonychia

• Traumatic/idiopathic: Reassurance, no treatment needed - will grow out with nail
• Hereditary: Traditionally no effective treatment, but intramatricial triamcinolone acetonide (5-10 mg/cc) shows promise for significant psychosocial burden 2
• Fungal: See onychomycosis treatment below

Apparent Leukonychia

Treat the underlying systemic condition - nail changes will resolve with correction of:

• Hypoalbuminemia (nutritional support, treat underlying cause)
• Renal failure (optimize dialysis, consider transplant)
• Liver disease (manage cirrhosis)
• Correct nutritional deficiencies

Toxic Leukonychia

• Remove exposure source immediately
• Arsenic poisoning: Chelation therapy may be indicated for acute/severe cases 4
• Supportive care for neuropathy if present

Pseudoleukonychia

• Gentle removal of surface deposits
• Avoid causative agents (nail polish, chemicals)

Critical Pitfalls to Avoid

1. Don't assume all white nails are fungal - this leads to unnecessary antifungal treatment. Always perform fungal testing before treating 6.

2. Don't miss systemic disease - Transverse white lines (especially Muehrcke's or Mees' lines) warrant evaluation for hypoalbuminemia, renal disease, or toxic exposure.

3. Don't confuse Muehrcke's lines (blanch with pressure, nail bed origin) with Mees' lines (don't blanch, nail plate origin) - this distinction guides whether to look for chronic disease vs. acute toxic exposure.

4. Don't biopsy hereditary leukonychia - it's a clinical diagnosis, and biopsy won't change management 3.

5. In cancer patients on targeted therapy, white nail changes may represent drug toxicity requiring dose adjustment or treatment modification 5.

When to Refer

• Leukonychia totalis with unclear etiology
• Suspected hereditary leukonychia with significant psychosocial impact (consider dermatology for intramatricial steroid injection)
• Systemic disease requiring specialist management
• Suspected malignancy (melanoma can rarely present with longitudinal leukonychia)