Abnormal pigmentation within cutaneous scars: A complication of wound healing

Abstract

Abnormally pigmented scars are an undesirable consequence of cutaneous wound healing and are a complication every single individual worldwide is at risk of. They present a challenge for clinicians, as there are currently no definitive treatment options available, and render scars much more noticeable making them highly distressing for patients. Despite extensive research into both wound healing and the pigment cell, there remains a scarcity of knowledge surrounding the repigmentation of cutaneous scars. Pigment production is complex and under the control of many extrinsic and intrinsic factors and patterns of scar repigmentation are unpredictable. This article gives an overview of human skin pigmentation, repigmentation following wounding and current treatment options.

Keywords: Melanin; melanogenesis; pigmentation; scar(s); wound.

Figure 1

Stages of melanosomal maturation. Melanosomes exist in four distinct stages as they become increasingly laden with melanin pigment prior to transport out of the cell into neighbouring keratinocytes via melanocyte dendrites. Histochemical markers which identify melanosomes at varying stages of development are useful in the diagnosis of melanocytic lesions

Figure 2

Melanogenesis is a complex process under the control of many genes. Key steps are activation of MITF-M, which leads to downstream activation of essential enzymes Tyrosinase, TRP1 and TRP2

Figure 3

Intrinsic regulation of melanogenesis. Melanogenesis is under the control of multiple extrinsic factors, from a variety of cell types. Communication between these cell types is essential for successful melanin production (Adapted from[50])

Figure 4

(a) Abnormal pigmentation within scars renders even flat, matt and supple scars more noticeable. The central hypopigmentation and peripheral hyperpigmentation can be clearly seen in this child's postburn scar (b) Abnormalities in pigmentation following injury are more pronounced in people with darker skin types. This child's postburn scar is centrally hypopigmented and peripherally hyperpigmented, making the scar highly noticeable against the surrounding unwounded skin

Figure 5

Melanocyte populations within the human hair follicle. There are multiple sites within the human hair follicle capable of producing melanocytes. The most important of these, the æbulgeæ region, houses the melanocyte stem cell reservoir