top of page

Benign Longitudinal Menlanoncyhia Radial (BLMR)

Author: Dr Annie Price

Chief Editor: Dr Daniel Keith

BLMR typically present as longitudinal bands consisting of multiple thickened, pigmented lines on the nail unit. It may involve single or multiple nails; affecting finger and toenails.

​

BMLR is the result of melanocytic activation, as opposed to melanocytic proliferation which is seen in acral lentiginous melanoma, for example.

​

Histopathological investigation represents the gold standard for definitive diagnosis due to the clinical ambiguity in differentiating BLMR from acral melanoma. 

Macroscopic Appearance

NB: When assessing melanonychia, it’s important to consider the following:

  • number of affected nails

  • pigment colour(s)

  • band borders

  • presence of longitudinal/transverse/total pigmentation

  • extension into the periungual tissue (Hutchinson’s sign)

  • additional nail signs.

image.png

Figure 1.

Multiple thickened, longitudinal pigmented bands on the great toenail.

Dermoscopic Appearance

Dermoscopy is useful for differentiating melanocytic and non-melanocytic nail pigmentation. Melanocytic pigmentation is typically brown-black and within the nail plate (see Figure 2). Subungual haematoma, for example, is one of the most common causes of non-melanocytic nail pigmentation and is identified on dermoscopy by the presence of red-brown globules which lack longitudinal lines.

 

Typical dermoscopic features of BLMR:

​

  • Regularly spaced parallel lines that are uniform in thickness

  • Homogeneous colour of the individual lines and background band

  • Proximal nail matrix pigmentation in which the pigmented band extends from the nail base to the nail tip

 

Atypical features of melanocytic pigmentation include multicoloured lines, oblique lines or total melanonychia (pigmentation of the whole nail plate). Micro-Hutchinson’s sign is an atypical dermoscopic finding which refers to pigmentation of the periungual tissues.

image.png

Figure 2.

Multiple vertical brown lines on the nail plate, arranged in a longitudinal band. The proximal and distal band ends are equal in width.

bottom of page