Laddering melanotic pattern of Langer's lines in skin of colour.

Mechanobiological stimulation of the skin influences melanocyte activity. The clinical impact on melanocytes can be perceived by dermoscopy. Our aim was to assess the orientation of Langer's lines using the combination of ultrasound shear wave propagation and dermoscopy in 70 adults of darker skin complexion. On the back, 44/70 patients showed a honeycomb melanotic pattern without any main orientation. By contrast, a streaky parallel pattern of melanotic lines oriented in the direction of Langer's lines was found in 26/70 patients. Indeed, the maximum speed of ultrasound propagation was found parallel to the main orientation of the laddering melanotic pattern. The parallel melanotic pattern probably reflects the main orientation of the epidermal rete ridges aligned in the direction of Langer's lines. This aspect could be ascribed to the deepening of these structures and/or to mechanobiology affecting melanocytes. The aspect is reminiscent of that previously described in striae distensae and atrophic scars.