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melanonychia; longitudinal melanonychia; melanonychia striata

Etiology: - subungual melanoma - physiologic longitudinal melanonychia - systemic disorders - trauma - inflammatory disorders - fungal infections - drugs (azidothymidine, minocycline, antimalarials, gold, chemotherapy) - benign melanocytic hyperplasias - lentigo Epidemiology: - prevalence increases with age - more common in darker pigmented individuals - ~100% of blacks > 50 years of age - in the general white population, prevalence is 1.4% Pathology: - increased production of melanin by melanocytes in nail matrix Clinical manifestations: - asymptomatic brown or black pigmentation of the nail - commonly presents as pigmented band arranged lengthwise along the nail - longitudinal brown lines may extend from tip of nail into the lunula - typically multiple nails are involved - a single nail with longitudinal melanonychia suggests an underlying melanocytic lesion (subungual melanoma) [3] - suspect melanoma when proximal nail fold involved (Hutchinson's sign) * images [1,2] Laboratory: - nail plate clipping for histologic analysis (KOH prep) & appropriate cultures if fungal infection suspected - nail matrix biopsy if subungual melanoma suspected [3] - > 3 mm in width - irregular or blurred borders to the band - brown black discoloration of the proximal nail fold (skin proximal to nail) Differential diagnosis: - subungual melanoma is the most serious concern - acral lentiginous melanoma (periungual pigmentation or Hutchinson's sign) - melanotic macule of the nail unit - nail matrix nevus - onychomycosis - subungual hematoma * also see brown nails Management: - refer to dermatology if subungual melanoma suspected - directed at underlying etiology - no treatment indicated for benign etiology

Specific

Laugier-Hunziker syndrome

General

melanocytic disorder brown nails; longitudinal brown lines; black nails

References

  1. Adigun C. James JD et al (images) Melanonychia http://emedicine.medscape.com/article/1375850-overview
  2. DermNet NZ: Melanonychia (images) http://www.dermnetnz.org/hair-nails-sweat/melanonychia.html
  3. Medical Knowledge Self Assessment Program (MKSAP) 17, 18. American College of Physicians, Philadelphia 2015, 2018.
  4. Jefferson J, Rich P. Melanonychia. Dermatol Res Pract. 2012;2012:952186 PMID: 22792094
  5. Alessandrini A, Dika E, Starace M, Chessa MA, Piraccini BM. Diagnosis of Melanonychia. Dermatol Clin. 2021 Apr;39(2):255-267. PMID: 33745638 Review.