Leukonychia (White Spots on Nails): Causes, Myths, and When to See a Doctor

Leukonychia — white spots or lines on nails — is common and usually benign. True leukonychia is in the nail plate; apparent leukonychia is in the nail bed.

Common Causes

1. Trauma (Most Common): Minor injury to nail matrix (manicure, biting, hitting) → air pockets in keratin → white spot. Appears weeks later (nail growth ~3 mm/mo).
2. Manicure/Pedicure Damage: Aggressive cuticle pushing, gel/acrylic removal.
3. Nutritional Deficiencies (Rare as sole cause): Zinc, calcium, protein, biotin — but usually other signs present.
4. Medications: Chemo (cyclophosphamide, doxorubicin), antimalarials, sulfonamides, retinoids.
5. Systemic Illness: Cirrhosis (Muehrcke's lines — paired white bands), hypoalbuminemia, renal failure (half-and-half nails), heart failure.
6. Fungal Infection (Onychomycosis): White/yellow patches, thickening, crumbling — usually distal/lateral.
7. Skin Diseases: Psoriasis (pitting, oil spots), lichen planus, alopecia areata.
8. Heavy Metal Poisoning: Arsenic (Mees' lines — transverse white bands), thallium.

Myths

• Calcium deficiency — not a direct cause; milk doesn't clear spots.
• Vitamin deficiency — rarely isolated leukonychia.

When to See a Doctor

• Spots persist >6 months (nail doesn't grow out).
• Multiple nails affected with bands/lines (Muehrcke's, Mees').
• Associated nail changes (thickening, detachment, color change).
• Systemic symptoms (fatigue, edema, abdominal pain).
• Recent chemo or toxin exposure.

Management

• Traumatic: Wait for grow-out (fingernails 6 mo, toenails 12–18 mo).
• Fungal: Topical/oral antifungal after confirmation (KOH, culture, PCR).
• Systemic: Treat underlying condition.

Single spots from minor trauma need no treatment. Patterns across nails deserve investigation.