Discolored Toenails 
Overview
Discoloration of one or more toenails is a common clinical finding. Toenails normally appear translucent or light pink, reflecting the color of the underlying nail bed. A change in color—ranging from white, yellow, brown, green, blue, to black—can be a sign of benign conditions (trauma, cosmetic staining) or pathology (fungal infection, systemic disease, or melanoma). Early evaluation is important to determine cause and prevent complications.


Etiology (Causes)
Toenail discoloration may result from a variety of local and systemic factors:
1. Infectious Causes
  • Onychomycosis (dermatophyte fungal infection)
    Most common cause of yellow or brown nail discoloration. Associated features include thickening, subungual debris, and onycholysis.
  • Bacterial infection (e.g., Pseudomonas aeruginosa)
    Leads to a green–black discoloration (“green nail syndrome”) and may occur with onycholysis or chronic moisture exposure.
2. Traumatic or Mechanical Causes
  • Subungual hematoma from acute trauma (sports, tight shoes) causes dark red, purple, or black nails due to bleeding under the nail plate.
  • Repeated microtrauma, as seen in runners or athletes, may cause yellow–brown discoloration and nail thickening.
3. Dermatologic & Inflammatory Disorders
  • Psoriasis can cause nail pitting, onycholysis, and “oil drop” (orange-brown) spots.
  • Lichen planus may result in longitudinal ridging, thinning, or dark discoloration.
4. Systemic or Metabolic Disorders
  • Yellow nail syndrome is characterized by thickened, yellow nails, lymphedema, and respiratory disease.
  • Systemic illnesses such as liver disease, renal failure, or certain chemotherapies can cause diffuse nail color changes.
5. Neoplastic Causes
  • Subungual melanoma can present as a new or changing pigmented streak (longitudinal melanonychia), often brown or black, sometimes with periungual pigmentation (Hutchinson’s sign). Early biopsy is critical.
6. Exogenous Causes
  • Cosmetic staining from nail polish or dyes
  • Chemical exposures such as silver nitrate, nicotine, or certain medications (e.g., minocycline) may lead to bluish or gray nails.


Diagnosis
A thorough evaluation includes:
  • History: Onset, trauma, systemic disease, medications, occupational exposures.
  • Physical exam: Color pattern, thickness, associated nail or skin changes, symmetry.
  • Laboratory / imaging tests (as indicated):
    • Fungal culture or KOH preparation to confirm onychomycosis.
    • Dermoscopy for pigmented lesions.
    • Biopsy for suspected melanoma or other neoplasms.


Treatment
Management depends on the underlying cause:
Infectious
  • Onychomycosis
    • First-line: Oral terbinafine or itraconazole for 12–16 weeks.
    • Alternatives: Topical efinaconazole, ciclopirox, or tavaborole for mild disease or when oral therapy is contraindicated.
  • Bacterial (Pseudomonas)
    • Topical antiseptics (e.g., acetic acid soaks), appropriate antibiotics, and keeping the nail dry.
Traumatic
  • Subungual hematoma
    • Small, painless: observation.
    • Painful or large: nail trephination or removal to relieve pressure.
    • Preventive measures: proper footwear, trimming nails short.
Dermatologic / Systemic
  • Treat underlying psoriasis, lichen planus, or systemic illness.
  • Yellow nail syndrome may improve with treatment of underlying lymphatic or pulmonary disease.
Neoplastic
  • Suspicious pigmented lesions require prompt biopsy and, if confirmed, melanoma excision with appropriate oncologic management.
Supportive & Preventive Care
  • Keep nails dry and well-trimmed.
  • Wear properly fitting shoes.
  • Avoid harsh chemicals and frequent nail polish application if recurrent staining occurs.


Expectations and Prognosis
  • Fungal infection: Complete nail clearing can take 6–12 months due to slow nail growth, even after effective therapy. Recurrence rates may exceed 20–30 %.
  • Traumatic hematoma: Typically resolves as the nail grows out (3–6 months for toenails).
  • Psoriasis or lichen planus: Chronic course; nails may improve with systemic or biologic therapy.
  • Melanoma: Prognosis depends on early detection and stage at diagnosis—timely intervention is critical.
  • Exogenous staining: Resolves as the nail grows if the causative exposure is removed.
Patients should be counseled that visible improvement is gradual, as toenails grow approximately 1–2 mm per month.


Key References (Peer-Reviewed)
  1. Gupta AK, Versteeg SG. Onychomycosis: current trends in diagnosis and treatment. Am J Clin Dermatol. 2017;18(6):733–744.
  2. Lipner SR, Scher RK. Onychomycosis: treatment and prevention of recurrence. J Am Acad Dermatol. 2019;80(4):853–867.
  3. Piraccini BM, Alessandrini A. Onychomycosis: a review. J Fungi (Basel). 2015;1(1):30–43.
  4. Phan A, Dalle S, Touzet S, Ronger-Savle S, Balme B, Thomas L. Dermoscopic features of subungual melanoma: a prospective study. Br J Dermatol. 2007;156(5):958–963.
  5. Haneke E. Nail psoriasis: clinical features, pathogenesis, differential diagnoses, and management. Dermatol Ther. 2012;25(6):463–481.
  6. Rockwell PG. Acute and chronic paronychia. Am Fam Physician. 2001;63(6):1113–1116.
  7. Baran R, Juhlin L. Green nail syndrome (chloronychia): Pseudomonas infection of the nails. J Am Acad Dermatol. 1987;16(5 Pt 1):931–933.​