What causes fingertip discoloration?

Causes of Fingertip Discoloration

Fingertip discoloration is most commonly caused by fungal nail infections (onychomycosis), bacterial infections (particularly Pseudomonas), vascular disorders (especially Raynaud's phenomenon), inflammatory skin conditions, or trauma—each requiring specific diagnostic confirmation before treatment.

Infectious Causes

Fungal Infections (Onychomycosis)

• Distal and Lateral Subungual Onychomycosis (DLSO) is the most common pattern, causing thickened, discolored nails with separation from the nail bed, affecting toenails more than fingernails 1, 2
• Superficial White Onychomycosis (SWO) presents as crumbling white lesions on the nail surface, particularly in children, usually caused by T. interdigitale 1
• Proximal Subungual Onychomycosis (PSO) causes discoloration starting from the proximal nail, is uncommon in the general population but frequent in immunocompromised patients, and may serve as a marker for HIV infection 1
• Total Dystrophic Onychomycosis represents advanced disease with near-complete nail plate destruction, typically requiring oral antifungal therapy 2
• Laboratory confirmation is essential: 50% of dystrophic nails are non-fungal despite similar appearance, requiring direct microscopy with potassium hydroxide preparation and fungal culture on Sabouraud's glucose agar 3

Candidal Infections

• Candida infections account for 5-10% of onychomycosis cases and more commonly affect fingernails than toenails 1
• Chronic paronychia with secondary nail dystrophy occurs in patients with wet occupations, causing swelling of the posterior nail fold, white/green/black marks, and nail plate involvement with proximal discoloration 1
• Distal Candida nail infection presents with onycholysis and less subungual hyperkeratosis than dermatophyte infections, nearly always associated with Raynaud's phenomenon or other vascular insufficiency 1

Bacterial Infections

• Green Nail Syndrome caused by Pseudomonas aeruginosa produces green or black discoloration, requiring keeping the area dry and applying topical povidone iodine 2% twice daily 1, 4
• Bacterial infections can coexist with fungal infections and may require independent treatment 1

Vascular Causes

Raynaud's Phenomenon

• Raynaud's phenomenon causes episodic vasospasm with characteristic triphasic color changes: white (vasoconstriction), blue (cyanosis), and red (hyperemia), triggered by cold or stress 5
• Affects 5-20% of the European population, four times more common in women, with average onset at age 40 6
• Primary Raynaud's disease occurs without underlying conditions, while secondary Raynaud's syndrome associates with systemic diseases like systemic lupus erythematosus 7, 8
• Distal Candida nail infection is almost exclusively seen in patients with Raynaud's phenomenon or vascular insufficiency 1
• Can lead to fingertip necrosis following minor trauma or surgical procedures 9

Acrocyanosis

• Characterized by persistent, painless bluish-red symmetrical discolorations of hands and feet, more common in women, manifesting before age 25 6
• Unlike Raynaud's, discoloration is non-paroxysmal and continuous rather than episodic 6

Inflammatory and Dermatologic Causes

Contact Dermatitis

• Irritant contact dermatitis (ICD) accounts for 80% of occupational hand dermatitis cases, caused by frequent hand washing, detergents, and chemical irritants 1
• Allergic contact dermatitis (ACD) results from sensitization to preservatives, surfactants, antimicrobial ingredients, or rubber accelerators in gloves 1
• Both can present with erythema, edema, vesicle formation, scaling, or lichenification affecting fingertips 1

Other Inflammatory Conditions

• Psoriasis causes nail changes including thinning, subungual hyperkeratosis, and onycholysis, often with less friability than fungal infections 1
• Lichen planus affects approximately 10% of patients with the condition, causing nail thinning, subungual hyperkeratosis, and discoloration 1

Traumatic and Occupational Causes

• Repetitive trauma causes distal onycholysis leading to colonization by infectious pathogens and nail plate discoloration 1
• Occupational exposure to irritants (bleach, detergents, hot water) increases risk of discoloration through barrier disruption 1
• Health care workers have an estimated 30% prevalence of occupational skin disease affecting hands due to frequent hand hygiene practices 1

Critical Diagnostic Pitfalls

• Never diagnose fungal infection based on appearance alone—laboratory confirmation with microscopy and culture is mandatory, as 50% of dystrophic nails are non-fungal 3
• Examine family members for fungal infections when onychomycosis is suspected, as household transmission is common 3
• Distinguish between nail trauma and infection by examining the nail bed after clipping: normal longitudinal epidermal ridges indicate trauma rather than infection 1
• Consider systemic diseases when evaluating fingertip discoloration, particularly in cases of Candida infection or atypical presentations 1, 8
• Bacterial superinfection commonly coexists with fungal infections and requires independent treatment 1

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