Vertical Hyperpigmentation Stripes on Nails in a Teenager
In teenagers, vertical hyperpigmented nail stripes (melanonychia striata) are most commonly benign, particularly in darker-skinned individuals, but require careful clinical evaluation to exclude subungual melanoma, with observation being the preferred approach for benign-appearing lesions. 1
Diagnostic Approach
Initial Clinical Assessment
Determine the most likely etiology by examining specific features:
- Ethnic/physiologic melanonychia is the most common cause in dark-skinned teenagers and presents with multiple nail involvement, uniform brown coloration, and bandwidth <3mm 1
- Evaluate for concerning features that suggest malignancy: abrupt onset, rapid growth, bandwidth >3mm, irregular borders, pigment variegation, single digit involvement, proximal widening (triangular shape), nail plate dystrophy, and Hutchinson sign (periungual pigment spread onto cuticle or nail folds) 1
- Assess for secondary causes including recent trauma, medications, endocrine disorders, or dermatological conditions like lichen planus or psoriasis 1, 2
Key Distinguishing Features
- Benign melanonychia typically shows uniform tan-to-brown coloration with sharp lateral borders and stable appearance over time 1
- Melanoma warning signs include age >50 years at onset (less common in teenagers), personal/family history of melanoma, and rapid changes in existing pigmented bands 1
- Fungal infection presents differently with nail thickening, friable texture, and discoloration rather than discrete longitudinal bands 3, 2
Diagnostic Testing
Laboratory confirmation is essential when fungal infection is suspected:
- Perform KOH preparation and fungal culture only if clinical features suggest onychomycosis (thickening, friability, discoloration affecting the entire nail) rather than melanonychia 3
- Dermoscopy can help differentiate melanocytic from non-melanocytic causes 4
- Nail matrix biopsy is indicated for suspicious lesions with melanoma warning signs, particularly in Caucasian patients where longitudinal pigmented streaks tend toward malignancy 5
Common Pitfall to Avoid
Do not assume fungal infection based on appearance alone - 50% of nail dystrophy cases are non-fungal, and melanonychia striata has a distinct longitudinal band pattern rather than diffuse discoloration 3, 2
Management Algorithm
For Benign-Appearing Melanonychia (Most Teenagers)
Adopt a conservative "wait-and-see" approach:
- Observation with serial photography every 3-6 months to monitor for changes in width, color, or borders 1
- Patient education about warning signs requiring immediate re-evaluation 1
- Prolonged follow-up is mandatory for early detection of possible malignant transformation 1
For Suspicious Lesions
Refer promptly to dermatology for evaluation and possible nail matrix biopsy if any melanoma warning signs are present 4
If Fungal Infection is Confirmed
Systemic antifungal therapy is required:
- Terbinafine (first-line): weight-based dosing of 62.5 mg daily if <20 kg, 125 mg daily for 20-40 kg, or 250 mg daily if >40 kg, for 6 weeks (fingernails) or 12 weeks (toenails) 3
- Itraconazole pulse therapy (alternative): 5 mg/kg/day for 1 week per month, for 2 pulses (fingernails) or 3 pulses (toenails) 3
- Baseline liver function tests are recommended before initiating systemic antifungal therapy 3
Preventive Measures
- Daily topical emollients to cuticles and periungual tissues help maintain nail health 2
- Avoid nail trauma and excessive moisture exposure 2
- Sun protection as recommended for general population if pigmentation is related to UV exposure 6
Critical Clinical Pearl
In teenagers, particularly those with darker skin types, multiple nail involvement with uniform pigmentation strongly suggests benign ethnic melanonychia - this is so common in dark-skinned individuals as to be considered a normal variant and requires only observation 7, 1