Pigmentary Demarcation Lines

 

Salient features

 

·       Lines of demarcation between dorsal surfaces (which are relatively hyper pigmented) and ventral surfaces

 

·       Physiologic pattern of human pigmentation

 

·       More often apparent in individuals with darkly pigmented skin

 

·       Most commonly seen on the anterolateral upper arm and posteromedial thigh

 

Introduction

 

Pigmentary demarcation lines (PDL), also known as Futcher's or Voight's lines are areas of abrupt transition from hyper pigmented to hypo pigmented or normal skin color. In all skin types, the dorsal skin surfaces are relatively hyper pigmented compared to the ventral surfaces. In individuals with darkly pigmented skin, visible lines of demarcation between dorsal and ventral surfaces are more conspicuous, especially on the anterolateral portion of the upper arm. These demarcation lines are bilateral, symmetric, and present from infancy through adulthood. Additional lines occur on the posteromedial aspect of the thighs, upper chest, paraspinal region of the back, and face

 

Facial PDL are divided into three types F, G and H. Line F denotes an inverted cone-shaped patch that extends from the lateral orbital rim and points inferiorly or inferolaterally. Line G is analogous to line F, but having two inverted cones with a rim of normal pigmentation in between that forms a W-shaped patch. Line H is a linear hyper pigmented patch which extends from the lateral corners of the mouth. Facial PDL may present around puberty and may persist unchanged throughout life. It should be differentiated from melasma and post inflammatory hyper pigmentation. Various initiating factors include hormonal changes at puberty, pregnancy and acute illnesses like chickenpox, typhoid fever and viral hepatitis.  Periorbital melanosis and facial pigmentary demarcation line-F may represent same spectrum of the disease.

Periorbital melanosis usually appears after puberty and is more common in certain ethnic groups. POM is frequently observed in multiple members of the same family. Facial PDL may have a genetic predisposition and become visible around puberty. It may appear from childhood but remain unnoticed and become prominent after exposure to triggering factors e.g. pregnancy or hormonal changes at puberty. Facial PDL-F has a prolonged course causing cosmetic concerns for the patients and a challenge for dermatologists.

 

Differential Diagnosis

 

POM and PDL-F are common chronic and same pigmentary conditions and should be considered as a single entity. PDL-F should be differentiated from other similar conditions like melasma, lichen planus pigmentosus, post inflammatory hyper pigmentation and drug-induced pigmentation.

 

PIH may occasionally be confused with pigmentary demarcation lines types A, B, D, and F–H. However, in the latter there is no preceding inflammation or injury and the lines are perfectly symmetric and stable over time. Types C and E pigmentary demarcation lines may be confused with linear nevoid hypopigmentation. Linea nigra, the linear hyper pigmentation that extends from the umbilicus to the pubis in pregnant women, is easily distinguished from a pigmentary demarcation line.

 

Treatment

 

These are normal pigmentation patterns, and no treatment is indicated.