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Longitudinal melanonychia - Nail and Distal Digit
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Longitudinal melanonychia - Nail and Distal Digit

Contributors: Vivian Wong MD, PhD, William M. Lin MD, Susan Burgin MD, Shari Lipner MD, PhD
Other Resources UpToDate PubMed

Synopsis

Longitudinal melanonychia describes a longitudinal band of pigment that extends from the nail matrix to the free edge of the nail. Melanonychia means "black nail." There are many causes of nail pigmentation (see Differential Diagnosis section) including skin diseases, systemic diseases, infections, trauma, medications, and pigmented lesions. While longitudinal melanonychia can have a benign etiology, it is critical to rule out acral lentiginous melanoma as a cause.

Melanocytes normally reside in the nail matrix and nail bed, though they are typically inactive in individuals of Northern European descent. In the nail matrix, if melanin production by melanocytes is greater than degradation by keratinocytes, the result is a longitudinal band. This phenomenon can be caused by melanocyte activation, melanocytic hyperplasia, lentigo simplex, melanocytic nevus, atypical melanocytic proliferations, and acral lentiginous melanoma.

Pediatric nail melanoma is extremely rare, particularly in individuals with Fitzpatrick phototypes I and II, but carries significant morbidity and mortality. The fingernails are more commonly involved than toenails. Evaluation of longitudinal melanonychia is more difficult in children than adults due to lack of clinical and histopathological guidelines. According to recent cohort studies from Asia, the majority of pediatric cases undergo regression or stagnation, and no incidence of melanoma was found in biopsied cases.

Codes

ICD10CM:
L60.8 – Other nail disorders

SNOMEDCT:
707196007 – Longitudinal melanonychia

Look For

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Diagnostic Pearls

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Differential Diagnosis & Pitfalls

Causes of longitudinal melanonychia:
Differential diagnosis of nail pigmentation:
  • Bacterial pigmentation, most commonly from Pseudomonas, Klebsiella, or Proteus, can have a greenish or grayish hue and is often located at the lateral edge of the nail.
  • Subungual hematoma is often the result of trauma and is most commonly found on the medial aspect of the first toe.
  • Exogenous nail pigmentation is most commonly caused by dirt, tobacco, potassium permanganate, and tar and typically does not cause a longitudinal streak. Most can easily be removed through physical means.

Best Tests

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Management Pearls

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Reviewed:05/17/2022
Last Updated:05/19/2022
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Longitudinal melanonychia - Nail and Distal Digit
A medical illustration showing key findings of Longitudinal melanonychia : Longitudinal brown-black nail bands
Clinical image of Longitudinal melanonychia - imageId=740351. Click to open in gallery.  caption: 'Several light grayish-brown longitudinal bands on the thumbnails.'
Several light grayish-brown longitudinal bands on the thumbnails.
Copyright © 2022 VisualDx®. All rights reserved.